摘要:

Journal of the Chemical Society, Faraday Transactions I ISSN 0300-9599Journal of the Chemical Society, Faraday Transactions I ISSN 0300-9599Abdulla, Mohammad A., Abou-Kais, Antoine, 1786-95 Abraham, Michael H., 359-65, Adams, Gayle E., 975-1001 Adams, Paul A., 1500-6 Agnew, Andrew, 2885-95, Aharoni, Chaim, 1507- 16 Ah-Sing, Eric, 359-65 Al-Ammar, Asad S., 195-205, Albeck, Michael, 1488-95, Albery, W. John, 1007-19 Alexander, Roger D., 1075-80, Allsopp, Stephen R., 1275-89 Amelitcheva, Tatiana M., Amira, Mohamed F., 1170-8 Anastasi, Christopher, 1693-701 Angeletti, Carlo, 1595-603 Angerstein-Kozlowska, Halina, Arakwa, Kazuo, 1953-62 Aronson, Michael P., 555-74 Arrowsmith, P., 3016-21 Asmus, Klaus-Dieter, 1820-6 Atri, Gulshan M., 366-79 Ayscough, Peter B., 5 1 1 - 18, Bailey, Ivy M., 1146-58 Baker, Richard R., 2229-51 Baldwin, Alan C., 2171-8 Baldwin, Roy R., 366-79, Ball, Matthew C., 1477-87 Bamford, Clement H., 1020-8, Bannard, John E., 153-62, Baranski, Andrzej, 146-52, Barker, Barry E., 1776-85 Barraclough,Peter B., 1360-72 Barrer, R.M., 1871-8 Barrer, Richard M., 745-55, Barrie, James A., 490-7 Barteri, Mario, 288-96 Barthomeuf, Denise, 1786-95 Barton, Allan F. M., 153-62 Basahel, Sulaiman N., 1020-8 Baumgartner, Erwin, 1 196-209 Bayliss, Stuart G., 776-84 Beekmans, Nico M., 31-45 Bennetto, H. Peter, 2385-92 Ben Taarit, Younes, 3000-7 Bertolini, Jean-Claude, 1720-5 Beunen, Joseph A., 2501-17 2873-84 1604-14,2101-10,2858-67 2896-906 657-64 1496-9 1081-8 306- 15 1373-89 248 1-9 1329-36,2229-5 1 1634-47,1648-54 163-73 2027-36 2786-97,2798-806 J.C.S.FARADAY I AUTHOR INDEX VOL. 74 (1978) 1 AUTHOR INDEX, 1978 Bezus, Arkadt G., 306-15 Bhattacharya, Ashok K., 1750-7 Bhattacharyya, Sudhindra N., Bickley, Roger I., 869-82 Birtwistle, David T., 2051-64 Blackley, David C., 205 1-64 Blackmore, David R., 765-75 Blanch, Jan H., 1254-62 Bleier, Alan, 1346-59 Bogaard, Martin P., 3008- 15 Bogomolova, Larisa L., 306- 15 Bombi, G. Giorgio, 1-9 Bone, Stephen, 720-6 Bonifacic, Marija, 1820-6 Booth, Colin, 2352-62 Borghesani, Gianna, 79-92 Bose, Kumardev, 105 1-63 Boucher, Ernest A., 427-31, Bouchy, Alain, 2652-66 Boughey, Marie T., 2200-9 Brady, John F., 2839-49 Brass, Ian J., 1556-61 Brett, Norman H., 1530-7 Briend-Faure, Marguerite, Brookes, Hugh C., 2193-9 Brooks, Brian W., 3022-6 Buckingham, A.David, 3008- 15 Buckland, Anthony D., Bucknell, James G., 1922-38 Buelow, Martin, 1210-20 Buisson, David H., 1081-8 Bullock, Anthony T., 727-32, Burch, Robert, 2982-90,299 1-9 Burdett, Nigel A., 53-62,63-70 Buxton, George V., 697-714 Cabani, Sergio, 2408- 17, Cadman, Philip, 2301-12 Cains, Peter W., 2689-702 Calado, Jorge C. G., 893-91 1 Caldin, Edward F., 1796-803, Caley, William F., 2942-5 1, Calvaruso, Giuseppe, 525-9 Cameron, G. Gordon, 727-32 Campbell, Ian M., 316-25, Capparelli, Albert0 L., 1834-48, Carabine, Michael D., 2689-702 Cargill, Robert W., 1444-56 Castiglioni, Mario, 8 18-26 Cataliotti, Rosario, 5 19-24 Cavasino, F. Paolo, 525-9 Ceckiewicz, Stanislaw, 146-52, 622-35 846-57 1538-44 2393-407 1556-6 1 2667-7 1 1804- 10,2065-9 2952-67 2672-7 1849-60 2027-36 Chadwick, Alan V., 2562-9 Chan, Chee-Yan, 2037-44 Chand, Anhai, 1768-75 Che, Michel, 1324-8,2378-84 Chee-Yan Chan, 837-45 Chemla, Marius, 2320-32 Chierico, Angelo, 2333-51 Chorng-Horng Twu, 893-91 1 Choudhury, Debendra N., Christensen, Bjarne, 23 13- 19 Cleaver, Brian, 686-96 Collin, Guy J., 1939-44 Coluccia, Salvatore, 1324-8, Compton, Richard G., 1007-19 Conti, Giovanni, 2408-17 Conway, Brian E., 1373-89, Cooke, Michael D., 2363-77 Cooney, Ralph P., 2542-9 Cooper, Peter G., 785-94 Cooper, W.David, 1583-9, Coppens, Henry J., 2193-9 Copperthwaite, Richard G., Cordischi, Dante, 456-65, Costenoble, Martin, 13 1-5 Costenoble, Martin L., 466-76, Coudurier, Gisele F., 3000-7 Couper, Aitken, 326-36 Cowell, Christopher, 337-47 Cox, Alan, 1275-89 Cox, Raymond G., 1242-53 Cremers, Adrien, 182-9, Cremers, Andrien, 136-45 Cross, Stephen N.W., 2130-40, Cullis, Charles F., 1922-38 Cundall, Robert B., 1339-45, Currie, John C., 1390-402 Cutler, Sidney G., 1758-67 Dalmai-Imelik, Gisele, 1720-5 Danil De Namor, Angela F., Darwent, Basil de B., 1545-55 Das, Asim K., 1051-63 Das, Bijoy K., 22-30 Das, Kaushik, 1051-63 Das, Prasanna K., 22-30 Davidson, Iain M. T., 2171-8 Davies, A. Keith, 181 1-19 Dawber, J. Graham, 960-3, Dawson, Ray B., 490-7 Deane, A. Michael, 2913-22 De Basttisti, Achille, 79-92 2868-72 2763-70,29 13-22 1390-402 2008- 16,227 1-7 2252-70 883-92 477-83 1234-41,2470-80 2141-5 1403-9 359-65,2101-10 1702-8, 1709- 192 J.C.S. FARADAY I AUTHOR INDEX VOL. 74 (1978) Delafosse, Denise, 1538-44 De Lisi, Rosario, 1096-1 11 De Visser, Cees, 1 159-69 Di Dio, Emanuele, 525-9 Donckt, E.Vander, 827-36 Druon, Christian, 530-7 Ducarme, Valentin, 506-8 Duckworth, Ralph M., 2200-9 Dudeney, A. William L., Dufaux, Michel, 440-9 Duffy, John A., 1410-19 Dunn, Lawrence A., 1 159-69 Dunning, Antony J., 2617-24 Ebeid, El Zeiny M., 1457-66 Ebel, Maria, 2092- 100 Ebert, Michael, 665-75 Egan, Karen L., 21 11-20 El-Bayoumi, M. Ashraf, Eley, Daniel D., 223-36 Eliezer, Isaac, 393-402 Elliot, A. John, 51 I-18,2111-20 Ellison, Alan, 2017-26,2807-17 Evans, Geoffrey A., 366-79, Evers, Edward L., 4 18-26 Failes, Robert L., 776-84 Farber, Milton, 1089-95 Farinella, Marcello, 288-96 Farrell, Patrick G., 858-68, Farrington, John A., 665-75 Feakins, David, 380-92 Fenby, David V., 1768-75 Fernandez-Prini, Roberto, Fiedler, Klaus, 2423-33 Figuera, Juan M., 809- 17 Figueras, Francois, 174-81 Foerster, Horst, 1435-43 Folman, Mordechai, 2935-41 Forrest, Jacques W., 2562-9 Fox, Katharine K., 220-2 Fox, Malcolm F., 1776-85 Freeman, John J., 758-61 Frey, Henry M., 1827-33 Friedman, Robert Mark, 758-61 Frost, Ray L., 583-96 Fuentes, Sergio, 174-8 1 Fujii, Yukio, 1467-76 Furukawa, Kazuo, 297-305, Fussey, David E., 1403-9 Gaggelli, Elena, 2 154-8 Gallina, Pietro, 5 19-24 Galuszka, Jan, 146-52,2027-36 Gans, Peter, 432-9 Gault, Francois G., 2652-66 Gault, Yvonne, 2678-88 Gelbin, David, 2423-33 Getoff, Nikola, 1029-35 Giles, Dennis, 733-44 Gill, Dip S., 1834-48, 1849-60 Gill, J.Bernard, 432-9 Giuffre, Luigi, 2 179-92 Goffredi, Mario, 1096-1 11 Gonzalez, Francisco, 1 5 17-29 Gray, Christopher G., 893-91 1 1075-80, 1081-8 1457-66 1329-36 1268-74 1 196-209,2460-9 795-803,804-8, 1861-70 Green, John C., 697-714 Green, Mino, 2724-41 Gregg, S.John, 348-58 Griffin, Mervyn, 432-9 Griffiths, David M., 403-17 Gstrein, Kurt H., 1002-6 Gubbins, Keith E., 893-91 1 Hall, Denver G., 1758-67 Hall, Peter G., 948-59, 1221-33, Halpern, Bret, 1883-912 Hamann, Sefton D., 2742-9 Handy, Brian J., 316-25, 2672-7 Harris, Kenneth R., 933-47 Harrison, Andrew J., 1403-9 Harrison, Philip G., 2597-603, Hayhurst, Allan N., 53-62, Hayon, Elie, 1776-85 Heaviside, John, 2542-9 Heckmann, Gernot, 71-8 Heggen, Inger, 1263-7 Hemidy, Jean F., 2763-70 Hendra, Patrick J., 2542-9 Herman, Jan A., 1939-44 Hertz, H. Gerhard, 1834-48, Heuvelsland, Wim J. M., Hibbert, D. Brynn, 1973-80, Hill, Tony, 359-65 Hillman, A.Robert, 1007- 19 Ho, Rickey Kam C., 46-52 Holz, Manfred, 644-56 House, William A., 1045-9, Howald, Reed A., 393-402 Hoyte, Otho P. A., 46-52 Hucknall, David J., 1922-38 Hunter, Robert J., 450-5 Hussein, Falah H., 2873-84 Iida, Yoichi, 190-4 Iijima, Toshiro, 2583-96 Imelik, Boris, 440-9 Indovina, Valerio, 456-65, Inel, Yuksel, 2301-12 Ingram, Malcolm D., 1410-19 Inui, Tomoyuki, 2490-500 Irvine, Elizabeth A., 1590-3 Irving, Elizabeth A., 206-10 Irving, Roger J., 1075-80, Isa, Saadoon A., 546-54 Israelachvili, Jacob N., Ito, Osamu, 1188-95 Iwasawa, Yasuhiro, 2968-8 1 James, Alan D., 10-21 James, David W., 583-96 James, Robert G., 1666-75 Jayson, Gerald G., 418-26 Jeanjean, Janine, 1538-44 John, Christopher S., 326-36, Johnson, Christopher A.F., 1360-72,2265-70 2604- 16,2703- 13 63-70, 7 15- 19 1849-60 1 159-69 1981-9 1 1 12-24 883-92 1081-8 975- 1001 498-505 2930-4 Johnson, David W., 964-74 Jones, Colin F., 1615-23, Jones, Malcolm N., 2923-9 Joyner, Richard W., 546-54 Kaerger, Joerg, 12 10-20 Kanemoto, Sho, 676-85 Kasrai, Masoud, 2452-9 Katayama, Akiko, 1963-72 Katsanos, Nicholas A., 575-80 Kelley, Barry P., 277 1-8, Kemp, Terence J., 1275-89 Kennedy, Lois V. F., 498-505 Kent, Henry J., 846-57 Kermarec, Maggy, 1538-44 Khoo, Kean H., 837-45, Khosravi Babadi, Ezatollah, Kijenski, Jacek, 250-61 King, Keith D., 912-18 Kirsch, L. J., 3016-21 Kirsch, Leslie J., 2293-300 Kiselev, Andrei V., 306- 15 Kita, Hideaki, 1963-72 Kittaka, Shigeharu, 676-85 Klaning, Ulrik K., 28 18-38 Klofutar, Cveto, 21 59-65 Kocirik, Milan, 1210-20 Koehler, Gottfried, 1029-35 Koga, Yoshikata, 1913-21 Komiyama, Jiro, 2583-96 Konar, Ranajit S., 1545-55 Kumakura, Minoru, 1953-62 Kumarasinghe, Sudath, 1036-44 Kundu, Kiron K., 1051-63 Lafferty, Joseph, 538-45,2760-2 Lambert, Graham, 2481-9 Lampard, Desmond, 1403-9 Land, Edward J., 538-45, Laschi, Franco, 21 54-8 Latzel, Johannes, 2092-100 Lauks, Iments R., 2724-41 Ledoux, Marc J., 2652-66 Lee, John A., 237-49 Lee, Munam, 1726-37, 1738-49 Lepori, Luciano, 2667-7 1 Levinger, Aron, 1488-95 Leyendekkers, J.V., 450-5 Li-In-On, Regs, 337-47 Lilley, Terence H., 1301-23, Lim, Tiong-Koon, 2037-44 Lima, M. Conceicao P., 1036-44 Lindblom, Goran, 1290-300 Lindman, Bjorn, 1290-300 Lindstrom, Jakob, 1263-7 Linford, Roger G., 2363-77 Linton, Max, 2742-9 Lips, Alexander, 733-44, 2200-9 Liszi, Janos, 1604-14,2858-67 Liveri, Vincenzo Turco, Lloyd, John, 2252-70 Lubezky, Aviva, 2935-41 1624-33 2779-85 2037-44 427-3 1 597-602,665-75,2077-91, 2760-2 277 1-8, 2779-85 1096-1 11J.C.S.FARADAY I AUTHOR INDEX VOL. 74 (1978) 3 Lutfullah, 93-102, 103-14, Lycourghiotis, Alexis, 575-80 McAlpine, Eoghan, 597-602 McAteer, James C., 2378-84 Macca, Carlo, 1-9 Maccoll, Allan, 2714-23 Maddock, Alfred G., 919-32 Maes, Andre, 13 1-5, 136-45, Makai, Alexander J., 2850-7 Malinowski, Stanislaw, 250-61 Mandel, Michel, 2339-5 1 Manning, Gary D., 2434-51 Marsden, Robert S., 1583-9, Marshall, Roger M., 2121-9 Mason, Stanley G., 1242-53 Massardier, Jean, 1720-5 Masson, Charles R., 2942-51, Matijevic, Egon, 1346-59 Matsuda, Minoru, 1 188-95 Matteoli, Enrico, 2408-17 Mau, Albert W.H., 603-12 Meares, Patrick, 1758-67 Melvin, Deirdre, 1337-8 Metcalfe, Alan, 1945-52 Metcalfe, Leonard P., 869-82 Metiu, Horia, 2750-4 M’Halla, Jalel, 2320-32 Mingins, James, 261 7-24 Minoura, Yuji, 1726-37, Mirodatos, Claude, 1786-95 Mitchell, D. John, 2501-17 Miura, Robert M., 1913-21 Mognaschi, Ezio R., 2333-51 Mollett, Christopher C., 427-31 Mollica, Vincenzo, 2667-71 Monk, Cecil B., 1170-8 Montague, Derek C., 262-76, Morgan, John A., 21 1-19 Mori, Toshio, 2583-96 Morigami, Tadashi, 1738-49 Morimoto, Tetsuo, 676-85 Morsi, Salah E., 1457-66 Mortier, Wilfried J., 466-76, Moyes, Richard B., 1666-75 Mruzek, Margaret N., 2714-23 Mueller, Shirley Ann, 948-59, Muhammad, Din, 9 19-32 Mullik, Sanam U., 1634-47, Munuera, Guillermo, 15 17-29 Nabardi, Bashir, 2452-9 Naccache, Claude, 440-9 Nagy, Janos B., 2210-28 Nagy, Otto B., 2210-28 Nakamura, Tetsuro, 804-8, Nakano, Yasuo, 2968-8 1 Nasehzadeh, Asadollah, 359-65 Navaratnam, Suppiah, 181 1-19 Naylor, Timothy D., 2352-62 Newnham, Colin E., 237-49 484-9 182-9, 1234-41,2470-80 2008- 16,227 1-7 2952-67 1738-49 277-87 477-83 2265-70 1648-54 1861-70 Niccolai, Neri, 2154-8 Nicol, Stuart K., 785-94 Niepce, Jean-Claude, 1530-7 Noller, Heinrich, 2092-100 Norfolk, David J., 1676-86 Norwood, Leslie S., 1477-87 Occhiuzzi, Manlio, 456-65, Ogasawara, Sadao, 2968-8 1 Ohgushi, Tatsuo, 613-21 Ohno, Hideo, 297-305,795-803, Okagawa, Akio, 1242-53 Okamoto, Byron Y., 1990-2007 Oldershaw, Geoffrey A., Omar, Musa M., 115-22 O’Neill, Peter, 1820-6 O’Shaughnessy, Denis A., Overbeek, J.Theodoor G., Page, Nicholas D., 2121-9 Palavra, Antonio M. F., Paliani, Giulio, 519-24 Paljk, Spela, 2 159-65 Palmer, T. Frank, 1339-45 Parkes, David A., 1693-701, Parravicini, Gianbattista, Parsons, Barry J., 181 1-19 Pasquet, Daniel, 530-7 Paterson, Russell, 93-102, Paz-Andrade, Maria I., 2923-9 Pearson, Edward J., 223-36 Pedriali, Rodolfo, 79-92 Peeters, G., 1871-8 Peigneur, Paul, 182-9,2550-6 1 Pelton, Arthur D., 2193-9 Pepe, Franco, 1595-603 Perez, Juan M., 809-17 Perry, Robert W., 1655-65 Pethica, Brian A., 2617-24 Pethig, Ronald, 720-6 Petrella, Giuseppe, 2070-6 Phillips, Glyn O., 18 1 1 - 19 Pierens, Raymond K., 3008-1 5 Pilpel, Neiton, 123-30 Pispisa, Basilio, 288-96 Pontani, Thomas, 71-8 Porta, Piero, 1595-603 Pottinger, Ruth, 1827-33 Praliaud, Helene, 3000-7 Price, Colin, 2352-62 Prieto, Juan A., 15 17-29 Primet, Michel, 2570-80 Princen, Henricus M., 555-74 Pmetz, Walter A., 2077-91 hlidori, Fernando, 79-92 Quddus, Mahmoud A., 686-96 Raie, Razieh M., 2452-9 Rajab, Naman S., 2352-62 Rayner, John G., 785-94 Reddy, N.Kausalya, 727-32 Reed, Michael D., 2171-8 883-92 804-8, 1861-70 1687-92 380-92 2637-5 1 893-91 1 2293-300 2333-51 103-14,484-9,2885-95, 2896-906 Reed, W. John, 1275-89 Rendall, Henry M., 1179-87 Richmond, Peter, 261 7-24 Ridler, Gweneth M., 1500-6 Ridler, Philip F., 1500-6 Roberts, M. Wyn. 546-54 Robertson, Andrew J. B., Robinson, Brian H., 10-2 1, Robinson, Peter J., 2755-9 Rochester, Colin H., 403- 17, Rode, Bernd M., 71-8, 1002-6 Rogers, Donald W., 46-52, Rogerson, John S., 2672-7 Rogne. Otto, 1254-62,1263-7, Rose, Mark A., 1221-33 Rosner, Daniel E., 1883-912 Ross, Hilary J., 2930-4 Ross, John, 2750-4 Roussy, Georges, 2652-66 Sacchetto, Giuseppe A., 1-9 Sacco, Antonio, 2070-6 Sakaguchi, Tokuhisa, 1 188-95 Salmon, G.Arthur, 5 1 1 - 18, Sanniez, William H. K., 123-30 Santini, Sergio, 519-24 Schoonheydt, Robert A., Schulte-Frohlinde, Dietrich, Schulz, Ronald A., 359-65 Scott, Kevin F., 2873-84 Scurrell, Michael S., 23 13- 19 Seelemann, Rudolf, 1435-43 Segall, Robert L., 1615-23, Sehested, Knud, 28 18-38 Shahidi, Fereidoon, 858-68, Shaik, Sason, 1496-9 Shankar, S. Ude, 1945-52 Shapiro, Jacob S., 776-84 Sharp, William B., 1373-89 Sheppard, John G., 1500-6 Sheppard, Richard N., 490-7 Shiff, Karmela, 1488-95 Shingu, Haruo, 2490-500 Shoniya, Natalia K., 306-15 Shubayeva, Marianna A., Shukla, Jagdish P., 2045-50 Simmie, John M., 1337-8 Sinclair, Roy S., 538-45, Sing, Kenneth S.W., 2017-26, Sioli, Giancarlo, 2 179-92 Skelhorne, Graham G., 2755-9 Skinner, Henry A., 2923-9 Smart, Roger St. C., 1615-23, Smith, Alan, 1687-92 Smith, Alec L., 1 179-87,2200-9 21 1-19 2625-36 1 125-36, 1 137-45,2130-40, 2141-5,2393-407 2868-72 1796-803,2065-9 964-74 2550-61 1820-6 1624-33,2907-12 1268-74 306- 1 5 597-602 2807- 17 1624-33,2907-124 J.C.S. FARADAY I AUTHOR INDEX VOL. 74 (1978) Smith, Ian W. M., 1693-701 Soares, Virgilio A. M., 893-91 1 Sobue, Kozo, 1467-76 Sommerville, Iain D., 1410-19 Somsen, Gus, 1 159-69 Spaziante, Placido Maria, Spencer, Philip N., 686-96 Spiro, Michael, 1036-44 Spitzer, Jan J., 756-7,2385-92, Splendorini, Luciano, 288-96 Spnngett, Michael J., 7 15- 19 Srisankar, Elappulli V., 622-35 Snvastava, R.D., 1089-95 Staples, Edwin J., 2530-41 Staveley, Lionel A. K., 893-91 1, Steenken, Steen, 1820-6 Stone, Frank S., 2278-92 Strauss, Imants M., 2146-53, Struve, Peter, 1210-20 Stubbersfield, Rita B., 2352-62 Suehiro, Masatoshi, 2490-500 Sugiarto, Herman, 1973-80 Sugiura, Toshio, 1953-62 Swallow, A. John, 41 8-26 Swan, Timothy, 1676-86 Swinbourne, Ellice S., 776-84 Symons, Martyn C. R., 2146-53 Tabourier, Pierre, 530-7 Tada, Akio, 498-505 Tagaki, Yoshiki, 804-8 Takagi, Yoshiki, 1861-70 Takaishi, Tetsuo, 613-21 Tanaka, Kazuko, 1879-8 1 Tanaka, Motoharu, 1467-76 Tanemoto, Kei, 804-8 Taylor, Duncan, 206- 10, 1590-3 Tayyab, M. Mohammad, Tejuca, L.Gonzalez, 1064-74 2 1 79-92 24 18-21 2363-77 25 18-29 25 18-29 348-58 Tench, Anthony J., 2378-84, Thompson, Peter T., 1301-23, Thornton, Edward W., Tiddy, Gordon J. T., 1290-300, Tiley, Peter F., 1655-65 Tiong-Koon Lim, 837-45 Tobar, Aurora, 809-1 7 Toffel, Peter, 1820-6 Tortschanoff, Karl, 1804-10 Townsend, Rodney P., 745-55 Trasatti, Sergio, 79-92 Trebilco, Deborah Anne, Trebilco, Deborah-Anne, Trombe, Jean-Christian, Trotman-Dickenson, Aubrey F. Truscott, T. George, 538-45, Tsai, Peter, 2542-9 Tseung, Alfred C. C., 1973-80, Tsiatsios, Athanasios, 575-80 Turkevich, John, 1064-74 Turner, J. C. Robin, 2839-49, Turner, Peter S., 1615-23, Turq, Pierre, 2320-32 Turyn, Daniel, 1196-209 Tutsch, Ruediger, 1834-48, Tye, Frank L., 237-49 Ueda, Takashi, 2490-500 Ungarish, Moshe, 1507- 16 Uytterhoeven, Jan B., 466-76, Van Beek, Wim M., 2339-51 2763-70,29 13-22 1990-2007 2597-603,2604- 16,2703- 13 2530-41 1 125-36, 1 137-45 2393-407 2786-97,2798-806 2301-12 597-602,2760-2 1981-9 2850-7 1624-33, 2907-12 1849-60 477-83,2550-61 Van Blokland, Peter H.G. M., Vansant, E. F., 1871-8 Van Vooren, C., 827-36 Vedrine, Jacques C., 440-9, Vincent, Brian, 337-47 Vinek, Hannelore, 2092-100 Volpe, Paolo, 8 18-26 Wacrenier, Jean Mane, 530-7 Waddington, David J., 2293-300 Walker, Raymond W., 366-79, Walker, Stanley, 2045-50 Walsh, Robin, 1146-58 Wa Muanda, Mukana, 2210-28 Wan, Jeffrey K. S., 21 11-20 Warren, John, 2045-50 Watelle, Ginette, 1530-7 Webb, Geoffrey, 195-205, Weingaertner, Hermann, Wells, Cecil F., 636-43, 1569-82 White, Allan H., 3008-15 White, Lee R., 2501-17 White, Neal C., 2625-36 Wigfield, Kenneth, 2393-407 Williams, John O., 1457-66 Wilson, Christopher J., Wood, Colin E.C., 1339-45 Wood, Robert H., 1301-23, Woolf, Lawrence A., 933-47 Woolley, Allan, 2293-300 Woolley, Robert L., 1420-34 Worswick, Richard D., 2363-77 Yamada, Haruka, 1562-8 Yamamoto, Yoichiro, 1562-8 Yoroki, Mitsugu, 1861-70 Yusa, Atsushi, 613-21 Zecchina, Adriano, 1324-8, Zhdanov, Sergei P., 306- 15 Zikanova, Arlette, 121 0-20 2637-51 506-8, 1786-95 1329-36,2229-5 1 657-64 1834-48 1796-803. 1990-2007 2278-92J.C.S. FARADAY I SUBJECT INDEX VOL. 74 (1978) 5 SUBJECT INDEX, 1978 ABSORPTION ABSTRACTION ACETIC ACID ACETONE ACETONITRILE Adsorption/absorption characteristics of caesium on oxidized stainless steel, 1420-34 Moderation of photochemically generated hot hydrogen atoms, 1687-92 Mechanism of ketonization of acetic acid on anatase Ti02 surfaces, 15 17-29 Infrared study of the adsorption of acetone on rutile, 403-17 Some properties of binary aqueous liquid mixtures.Apparent molar volumes and heat capacities at 298. Hydrogenation of acetylene over supported metal catalysts. Part 1. Adsorption of acetylene-14C and Hydrogenation of acetylene over supported metal catalysts. Part 2. Carbon-14 tracer study of Shock tube studies of the high temperature pyrolysis of acetylene and ethylene, 1403-9 Evolution of adsorbed species during acetylene adsorption on nickel( 1 11) in relation to their vibrational Adsorption and polymerization of acetylene on oxide surfaces. A Raman study, 2542-9 Effect of temperature on the acid dissociation constants of 1 ,lo-phenanthroline and some related bases Reactions of some simple a- and 8-hydroxyalkyl radicals with cupric and cuprous ions in aqueous Effect of pressure on the electrical conductivities of some molten €3-group metal iodides and iodine, Model of polarisable spheres: a reappraisal, 756-7 Activity coefficients for the system hydrogen chloride + barium chloride + water at 298.15 K.Correlation of the catalytic activities of oxides with their work functions. Recombination of oxygen Activity coefficients for the system hydrogen chloride + cobalt chloride + water at 298.15 K. Effects of Application of polymer theory to silicate melts. The system metal(I1) oxide + metal(I1) fluoride + silica, Thermodynamics and constitution of silicate melts.The system lead monoxide + lead difluoride + Analysis of activity data in three component systems by means of an augmented Redlich-Kister Rapidly converging activity expansions for representing the thermodynamic properties of fluid systems: Correlation of the catalytic activities of oxides with their work functions. Recombination of oxwen 15 K over the whole mole fraction range, 1 159-69 ethylene-1% on silica supported rhodium, iridium and palladium and alumina supported palladium, 195205 deactivation phenomena, 657-64 spectra, 1720-5 ACETYLENE ACID DISSOCIATION CONSTANT in water, 1075-80 solution. Radiation chemical study, 697-7 14 686-96 ACTIVITY ACRYLAMIDE ACTIVATION VOLUME Comparison of Scatchards and Pitzer’s interpretations, 837-45 atoms on lithium(1 +) doped nickel oxides, 1750-7 higher-order electrostatic terms, 2 0 3 7 4 2942-5 1 silica, 2952-67 ACTIVITY COEFFICIENTS formalism, 393-402 gases, nonelectrolyte solutions, weak and strong electrolyte solutions, 1301-23 ACTIVITY EXPANSION ADSORBATE - - atoms on lithium( 1 +j doped nickel oxides, 1750-7 ADSORPTION Adsorption of butane- 1,4401 at the mercury-aqueous solution interface.Transition with polarization between two ideal adsorption models, 79-92 Hydrogenation of acetylene over supported metal catalysts. Part 1. Adsorption of acetylene-14C and ethy1ene-W on silica supported rhodium, iridium and palladium and alumina supported palladium, 195-205 Test of the nonane method for micropore evaluation. Use of nitrogen, n-hexane and carbon tetrachloride as adsorptives with ammonium phosphomolybdate, phosphotungstate and silicomolybdate as absorbents, 348-58 Role of Brcknsted acid centres for alkene double bond migration over alumina at temperatures above 450 K, 498-5056 J.C.S.FARADAY I SUBJECT INDEX VOL. 74 (1978) Study by electron paramagnetic resonance of charge-transfer complexes formed by adsorption of TCNE Adsorption of carbon monoxide on copper (100) studied by photoelectron spectroscopy and low energy Thermodynamics of adsorption based on gas-solid chromatography, 575-80 Hydrogenation of acetylene over supported metal catalysts. Part 2. Carbon-14 tracer study of Interaction of water molecules with the surface of tin(1V) oxide, 676-85 Electron spin resonance studies of the formation and thermal stability of oxygen radicals on calcium Physical adsorption of gas mixtures of 2,24imethylpropane and n-butane on Vycor glass and on Investigation of the surface heterogeneity of maximally hydroxylated nonporous silica by gas adsorption, Infrared study of the adsorption of anisoles on silica immersed in heptane, 1125-36 Infrared study of the adsorption of phenols on silica immersed in heptane, 1 137-45 Intercrystalline molecular transport in zeolites studied by uptake experiments and by nuclear magnetic resonance pulsed field gradient techniques, 12 10-20 Dielectric properties of water adsorbed by kaolinite clays, 1221-33 Electron paramagnetic resonance study of electron transfer at the surface of alkaline earth oxides.Reversible pyridine-induced formation of superoxide ions labelled with oxygen-17, 1324-8 Heterocoagulation.Part 3. Interactions of polyvinyl chloride latex with Ludox HS silica, 1346-59 Adsorption of water vapour by silica and the effect of surface methylation, 1360-72 Isomerization of n-butenes on A-type zeolites studied by infrared spectroscopy. Part 1. n-Butene Evolution of adsorbed species during acetylene adsorption on nickel( 1 1 1) in relation to their vibrational Characterization of the hydroxyls in offretite zeolite, 178695 Infrared studies of ethanol adsorbed on porous glass, 1945-52 Adsorption of hydrogen on a platinum-graphite catalyst. Part 1. Electron spin resonance measurement Infrared study of the adsorption of diketones on silica immersed in carbon tetrachloride, 2130-40 Infrared study of the adsorption of linoleic acid on alumina immersed in carbon tetrachloride, 2141-5 Adsorption of gas mixtures of 2,24imethylpropane and n-butane on graphite and application of ideal Reflectance spectra of carbon monoxide adsorbed on alkaline earth oxides, 2278-92 Infrared study of adsorption on silica from two-component and three-component liquid mixtures, Adsorption and polymerization of acetylene on oxide surfaces.A Raman study, 2542-9 Tin oxide surfaces. Part 4. Infrared study of the adsorption of oxygen and carbon monoxide + oxygen mixtures on tin(1v) oxide, and the adsorption of carbon dioxide on ammonia-pretreated tin(1v) oxide, 2597-603 Tin oxide surfaces. Part 9. Infrared study of the adsorption of carbon monoxide, nitric oxide and their mixtures on tin(Iv) oxide gels containing ion-exchanged chromium(III), manganese(II), iron(III), cobalt(II), nickel(I1) and copper(II), 2703-1 3 Luminescence and other spectroscopic studies of the reaction of pyridine and oxygen with thermally activated strontium oxide, 2763-70 Infrared spectra of nitric oxide, nitrous oxide, nitrogen dioxide and oxygen adsorbed on silicon monoxide films, 2935-41 Surface properties and catalytic activity of a molybdenum-fixed catalyst.Structure of the active site and mechanism for selective oxidation of ethyl alcohol, 2968-8 1 Structural characterization of high surface area reduced molybdenum oxide catalysts, 299 1-9 Oxidation of sulphur dioxide in aerosol droplets, catalysed by manganous sulphate, 2689-702 Fourier inversion of light scattering intensity data from coagulating dispersions, 11 12-24 Aqueous solutions containing amino acids and peptides.Part 8. Gibbs free energy of interaction of Kinetics, thermochemistry and mechanism of hydrogenolysis of aliphatic aldehydes on nickel-silica, Electron paramagnetic resonance study of electron transfer at the surface of alkaline earth oxides. Reflectance spectra of carbon monoxide adsorbed on alkaline earth oxides, 2278-92 Photoluminescent spectra of surface states in alkaline earth oxides, 29 13-22 on type X- and Y-zeolites, 530-7 electron diffraction, 546-54 deactivation phenomena, 657-64 oxide and some other oxides, 883-92 spherisorb silica, 948-59 1045-9 adsorption on zeolites containing alkali and alkaline earth cations, 1435-43 spectra, 172&5 in the gas-solid system, 1963-72 adsorbed solution theory, 2265-70 2393-407 AEROSOL AGGREGATE STRUCTURE ALANINE some a,co-amino acids with sodium chloride at 298.15 K, 2779-85 2873-84 ALDEHYDE ALK EARTH Reversible pyridine-induced formation of superoxide ions labelled with oxygen-17, 1 324-8 ALK EARTH OXIDEJ.C.S.FARADAY I SUBJECT INDEX VOL. 74 (1978) 7 ALKALI pV-T studies on molten alkali nitrates. Part 1. Thermal pressure coefficients and compressibilities, Water+-water isotope effect on nuclear magnetic relaxation of alkali halide nuclei and preferential solvation in mixed solvents, 644-56 Aqueous solutions containing amino acids and peptides. Part 5. Gibbs free energy of interaction of glycine with some alkali metal chlorides at 298.15 K, 2771-8 Lithium-7, sodium-23, and beryllium-9 nuclear magnetic resonance investigations of the influence of N- substitution on the solvation interaction of amides with alkali and alkaline earth metal ions, 7 1-8 Washburn numbers.Part 3. Alkali-metal chlorides in the DMSO + water system; comparison with p-V-T studies on molten alkali nitrates. Part 1. Thermal pressure coefficients and compressibilities, pV-T studies on molten alkali nitrates. Part 2. Internal energies and equation of state, 163-73 Structural analysis of some molten materials by X-ray diffraction. Part 4. Alkali nitrates RN03(R = Lithium- 7, sodium-23, and beryllium-9 nuclear magnetic resonance investigations of the influence of N- Thermodynamics of adsorption based on gas-solid chromatography, 575-80 Rayleigh scattering depolarization ratio and the molecular polarizability anisotropy for gases, 3008-1 5 1 53-62 ALKALI BROMIDE ALKALI CHLORIDE ALKALI METAL ALKALI METAL CHLORIDE hydrochloric acid; structural effects, 380-92 4LKALI METAL NITRATE 153-62 ALKALI NITRATE lithium, sodium, potassium, rubidium, caesium, and silver), 297-305 substitution on the solvation interaction of amides with alkali and alkaline earth metal ions, 71-8 ALKALINE EARTH METAL ALKANE ALKENE Characterization of supported platinum, hydrogenation and hydrogen-deuterium equilibration, 1064-74 ALKYL HALIDE Very low pressure pyrolysis (VLPP) of 3-chloropropionitrile, 9 12-1 8 Rayleigh scattering depolarization ratio and the molecular polarizability anisotropy for gases, 3008-1 5 Kinetic electron spin resonance spectroscopy.Part 6. Formation and termination reactions of aliphatic Reactions of alkyl radicals with nitrogen trifluoride, 2301-12 Kinetic isotope effects in the reactions of 4-nitrophenylnitromethane with alkylamidine bases in toluene, Partial molar volumes and viscosity of benzene solutions of tertiary n-alkylammonium picrates, 2 159-65 Low temperature infrared spectroscopic study of the solvation of ions in water, 2518-29 Flash photolysis study of the spectra of methyl peroxy and tert-butyl peroxy radicals and the kinetics of Kinetics of quaternizalion of &methyl and 4-ethyl pyridine with n-propyl and n-butyl bromide in Gas phase pyrolysis of cyclopropene. Part 1. Kinetics and mechanism, 1 146-58 Allene isomerization, 1337-8 Surface properties and catalytic activity of a molybdenum-fixed catalyst. Structure of the active site and Role of Broensted acid centres for alkene double bond migration over alumina at temperatures above Reexamination of the diffuse reflectance spectra of copper/alumina catalysts, 758-61 Electron spin resonance studies of the formation and thermal stability of oxygen radicals on calcium Characterization of supported platinum, hydrogenation and hydrogen-deuterium equilibration, 1064-74 1’- Radiolysis of methane adsorbed on y-alumina. Part 2.Kinetics of reactions occurring during Magnetic and optical studies of chromium oxides. Part 2. Calcination of chromic chloride supported on Infrared study of the adsorption of linoleic acid on alumina immersed in carbon tetrachloride, 2141-5 ALKYL RADICAL radicals by reductive dissociation of halogeno-compounds, 248 1--9 ALKYL RADICAL ABSTRACTION ALKY LAMIDINE 1796-803 ALKYLAMMONIUM PICRATE ALKYLAMMONIUM SALT ALKYLPEROXY RADICAL their mutual reactions and with nitric oxide, 1693-701 ALKYLPYRIDINE sulpholane, 427-3 I ALLENE ALLY LMOLY BDENUM mechanism for selective oxidation of ethyl alcohol, 2968-8 1 ALUMINA 450 K, 498-505 oxide and some other oxides, 883-92 irradiation, 1676-86 alumina, 20 1 7-268 J.C.S.FARADAY I SUBJECT INDEX VOL. 74 (1978) Adsorption and polymerization of acetylene on oxide surfaces. A Raman study, 2542-9 Infrared study of carbon monoxide chemisorption on zeolite and alumina supported rhodium, 2570-80 Magnetic and optical studies of chromium oxides.Part 3. Calcination of coprecipitated chromium and Magnetic and optical studies of chromium oxides. Part 3. Calcination of coprecipitated chromium and Thermodynamics of adsorption based on gas-solid chromatography, 575-80 Aqueous solutions containing amino acids and peptides. Part 8. Gibbs free energy of interaction of Partial molar volumes of organic compounds in water. Part 5. Betaines of a,o-aminocarboxylic acids, Partial molar volumes of organic compounds in water. Part 4. Aminocarboxylic acids, 858-68 Luminescence excitation and de-excitation involving one-electron transfer. Aqueous solutions of 1- Thermodynamic study of disorder in mercury(I1) diamminodichloride and mercury(I1) Complexes of ammonia and ethylenediamine with copper(I1) on zeolite A, 2550-61 Transition metal ion exchange in zeolites.Part 3. Ternary exchange in mordenite involving ammonium, Mechanism of ketonization of acetic acid on anatase Ti02 surfaces, 1 5 17-29 Infrared study of the adsorption of anisoles on silica immersed in heptane, 1125-36 Semiconducting oxides: effects of electronic and surface structure on dissolution kinetics of nickel oxide, Semiconducting oxides: infrared and rate studies of the effects of surface blocking by surfactants in Radicals derived from 1 ,Hisubstituted anthraquinones. Further evidence for association of quinones in Acidic properties of mixed tin + antimony oxide catalysts, 206-10 Dehydrogenation and isomerization of n-butenes on mixed tin + antimony oxide catalysts, 1590-3 Calculations on ionic solvation.Part 2. Entropies of solvation of gaseous univalent ions using a one- Examination of activation parameters for the dissociation of iron(II1) complexes as a means of assessing Percolation of gases into (potassium, calciumbA zeolites and their cation distribution, 61 3-21 Investigation of the surface heterogeneity of maximally hydroxylated nonporous silica by gas adsorption, Modified zeolites. Part 2. Sorption by dealuminated, silanated mordenites, 2798-806 Molecular interaction between iodine monochloride and diphenyl sulphides. A vibrational study, 5 19-24 New three-parameter empirical extension of the Arrhenius equation suitable for the precise evaluation of Mechanism of exchange in the manganese(I1tATP system from Fourier transform-nuclear magnetic Evidence for a molecular component in the thermal decomposition of azomethane, 21 21-9 Self-reactions of isopropylperoxy radicals in the gas phase, 2293-300 Activity coefficients for the system hydrogen chloride + barium chloride + water at 298.15 K.ALUMINIUM aluminium hydroxide gels, 2807-17 aluminium hydroxide gels, 2807-1 7 ALUMINIUM HYDROXIDE ALUMINIUM OXIDE AMINO ACID some a,o-amino acids with sodium chloride at 298.15 K, 2779-85 AMINOCARBOXYLATE 1268-74 AMINOCARBOXYLIC ACID AMINON APHTHALENESULPHONATE aminonaphthalene-4-(sodium)sulphonate, 2077-9 1 AMMINEMERCURY HALIDE diamminodibromide, 2363-77 AMMONIA AMMONIUM MORDENITE triethanolammonium and complexed nickel(II), 745-55 ANATASE CATALYST ANISOLE ANNEALING 1615-23 dissolution kinetics, 162433 ANTHRAQUINONE solution, 597-602 ANTIMONY APROTIC SOLVENT layer continuum model, 2858-67 mechanistic ambiguities.Data for phenolic complexes, 525-9 AQUATION ARGON 1045-9 AROMATIC SULPHIDES ARRHENIUS EQUATION ATP pseudothermodynamic activation parameters in chemical kinetics, 1 500-6 resonance and electron paramagnetic resonance data, 21 54-8 AZOMETHANE AZOPROPANE BARIUM CHLORIDE 100290 k17358J.C.S. FARADAY I SUBJECT INDEX VOL. 74 (1978) 9 Comparison of Scatchard’s and Pitzer’s interpretations, 837-45 BARIUM OXIDE Reflectance spectra of carbon monoxide adsorbed on alkaline earth oxides, 2278-92 Photoluminescent spectra of surface states in alkaline earth oxides, 291 3-22 Acid-base properties of molten oxides and metallurgical slags, 14 10- 19 Correlation between results of X-ray photoelectron spectroscopic studies and catalytic behaviour of Characterization of supported platinum, hydrogenation and hydrogen-deuterium equilibration, 1064-74 Patterns of activity in the benzenedeuterium exchange reaction and the hydrogenation of benzene Partial molar volumes and viscosity of benzene solutions of tertiary n-alkylammonium picrates, 21 59-65 Solvent effect on the dimerization and hydration constant of benzoic acid, 1467-76 Influence of applied electric fields on the free radical copolymerization of methylmethacrylate and Electronic absorption spectra of benzoyl radicals produced from benzoyl halides by irradiation with 7- Reactions of presolvated electrons and hydrogen atoms with benzyl chloride in methanol.A pulse Aqueous solutions containing amino acids and peptides.Part 8. Gibbs free energy of interaction of Partial molar volumes of organic compounds in water. Part 5. Betaines of a,waminocarboxylic acids, Solid state reversible reactions. Thermal behaviour of the photoisomer of bi(anthracene-9,lc Electrochemical decomposition of biformylperoxide. A quantum mechanical calculation, 1496-9 Thermodynamic study of dilute aqueous solutions of organic compounds. Part 5. Open-chain saturated Some properties of binary aqueous liquid mixtures. Apparent molar volumes and heat capacities at 298. Magnete-optical rotation studies of the structural properties of liquid mixtures. Part 1. Binary mixtures Magnete-optical rotation studies of the structural properties of liquid mixtures. Part 2. Binary mixtures Inorganic photophysics in solution.Part 1. Temperature activation of decay processes in the BASICITY magnesium oxide, 2092-100 BENZENE catalysed by evaporated metal films, 1666-75 BENZOIC ACID BENZOYL PEROXIDE styrene. An unusual decomposition of benzoylperoxide, 1488-95 rays in organic glass, 1 188-95 radiolysis study, 964-74 some cr,o-amino acids with sodium chloride at 298.15 K, 2779-85 BENZOYL RADICAL BENZYL CHLORIDE BETA BETAINE 1268-74 BIANTHRACENEDIMETHYLENE dimethylene), 603-1 2 BIFORMYL PEROXIDE BIFUNCTIONAL ALIPH bifunctional compounds, 2667-7 1 15 K over the whole mole fraction range, 1 15949 of alcohols, carboxylic acids, ethers and acetone with water, 1702-8 of some miscible organic components, 1709-19 luminescence of tris(2,2’-bipyridine)ruthenium(II) and tris( 1, 10-phenanthroline)ruthenium(II) ions, 1275-89 Spectrophotometric investigations of aqueous solutions at elevated temperatures.Effect of temperature on the stability constants of the tris complexes of 1 ,lO-phenanthroline, 5-nitro-1, lcphenanthroline and 2,2’-bipyridyl with iron (11), 1081-8 Bipyridylium quaternary salts and related compounds. Part 6. Pulse radiolysis studies of the reaction of paraquat radical analogues with oxygen, 665-75 Effect of pressure on the electrical conductivities of some molten B-group metal iodides and iodine, 686-96 Kinetics and mechanism of fast metal-ligand substitution processes in aqueous and micellar solutions Stability of metal uncharged ligand complexes in ion exchangers. Part 2. The copper + ethylenediamine Investigation of the size distribution of nonionic micelles formed from a polystyrene-polyisoprene block BINARY MIXT BIPYRIDINE BIPYRIDYL BIPYRIDYLIUM BISMUTH IODIDE BISPYRIDINEAZODIMETHYLANILINE studied by means of a dye-laser photochemical relaxation technique, 2625-36 complex in montmorillonite and sulphonic acid resin, 182-9 copolymer in N,N-dimethylacetamide, 235242 BJERRUM COMPLEX FORMATION FUNCTION BLOCK COPOLYMER10 J.C.S.FARADAY I SUBJECT INDEX VOL. 74 (1978) BOND ENERGY Mass spectrometric determination of the heats of formation of the silicon fluorides SiF(g), SiF*(g) and Flame photometric determinations of diffusion coefficients. Part 6. Results for carbon monoxide and Cyclization in the gas phase photolysis of neopentyl bromide, 776-84 Carbon difluoride emission during vacuum ultraviolet photodissociation of dibromodifluoromethane, Moderated copolymerization.Part 2. Transfer constant of styryl radicals towards carbon tetrabromide: Product crystallite size-reaction rate relationship in M(OH)*-MO decomposition. Structural pH calibration of tetroxalate, tartrate and phthalate buffer solutions at above IOO'C, 2434-5 I Percolation of gases into (potassium, calciumkA zeolites and their cation distribution, 61 3-21 Physical adsorption of gas mixtures of 2,24imethylpropane and n-butane on Vycor glass and on Molecular decomposition of 2,2,3,3-tetramethylbutane, 1329-36 Adsorption of gas mixtures of 2,24imethylpropane and n-butane on graphite and application of ideal Adsorption of butane--] ,Mi01 at the mercury-aqueous solution interface. Transition with polarization Calculation of dispersion force interactions between colloidal particles in butan--l-o1,2008-16 Colloid stability in butanol, 2271-7 Active centres on sodium hydrogen-Y zeolite in but-l-ene transformations, 14&52 Isomerization of n-butenes on A-type zeolites studied by infrared spectroscopy.Part 1. n-Butene Fourier transform infrared spectroscopy of the zeolite NaH-Y + but-1-ene system, 2027-36 Reactions of n-butenes on palladium films. Evidence for n-allylic species, 2652-66 Kinetics of quaternization of &methyl and k t h y l pyridine with n-propyl and n-butyl bromide in Decomposition of 2,2,3,3-tetramethylbutane in the presence of oxygen, 366-79 Kinetic analysis of deuteron-transfer reactions of alkylamidines with (2H2)4nitrophenylnitromethane. Adsorption of water vapour by silica and the effect of surface methylation, 1360-72 Transport in aqueous solutions of Group IlB metal salts (298.15K).Part 3. Isotopic diffusion Transport in aqueous solutions of Group IIB metal salts (298.15 K). Part 4. Interpretation and Product crystallite size-reaction rate relationship in M(OH)z-MO decomposition. Structural Stability constants for cadmium iodide complexes in aqueous cadmium iodide (298.15 K), 484-9 Effect of pressure on the electrical conductivities of some molten B-group metal iodides and iodine, Adsorption/absorption characteristics of caesium on oxidized stainless steel, 1420-34 Magnetic and optical studies of chromium oxides. Part 3. Calcination of coprecipitated chromium and Electron spin resonance studies of the formation and thermal stability of oxygen radicals on calcium Reflectance spectra of carbon monoxide adsorbed on alkaline earth oxides, 2278 -92 SiF3(g), 1089-95 free atoms of bromine, iodine, and thallium, 715-19 BROMINE BROMODIMETHY LPROPY L RADICAL BROMOFLUOROMETHANE 2930-4 BROMOMETHANE a penultimate unit effect in chain transfer, 1020-8 transformation mechanism, 1530-7 BRUCITE BUFFER BUTANE spherisorb silica, 948-59 adsorbed solution theory, 2265-70 between two ideal adsorption models, 79-92 BUTANEDIOL BUTANOL BUTENE adsorption on zeolites containing alkali and alkaline earth cations, 143543 BUTYL BROMIDE sulpholane, 427-3 1 BUTYL RADICAL BUTY LAMIDINE Implications of isotopic scrambling for the determination of kinetic isotope effects, 1254-62 CABOSIL CADMIIJM coefficients for cadmium-1 15 ions in aqueous cadmium iodide, 93-102 prediction of isotopic diffusion coefficients for cadmium in dilute solutions of cadmium iodide, 103-14 transformation mechanism, 1530-7 CADMIUM HYDROXIDE CADMIUM IODIDE 68696 CAESIUM CALCINATION aluminium hydroxide gels, 2807--17 oxide and some other oxides, 883-92 CALCIUM OXIDEJ.C.S.FARADAY I SUBJECT INDEX VOL. 74 (1978) 11 Photoluminescent spectra of surface states in alkaline earth oxides, 291 3-22 Studies in the system calcium sulphate monohydrate. Part 6. Surface chemistry and porosity of the Open-end capillary method in tracer and diffusion of electrolyte solutions, 2320-32 Origin of charge on colloidal particles in butanol, 1583-9 Calculation of dispersion force interactions between colloidal particles in butan-l-ol,2oO8-16 Colloid stability in butanol, 2271-7 Studies of reactions of atoms in a discharge flow stirred reactor. Part 2.Oxygen atom + dihydrogen + carbon monoxide system, 3 16-25 Adsorption of carbon monoxide on copper (100) studied by photoelectron spectroscopy and low energy electron diffraction, 546-54 Flame photometric determinations of diffusion coefficients. Part 6. Results for carbon monoxide and free atoms of bromine, iodine, and thallium, 7 15-19 Effect of lead compounds on heterogeneous oxidation catalysts, 1922-38 Reflectance spectra of carbon monoxide adsorbed on alkaline earth oxides, 2278-92 Infrared study of carbon monoxide chemisorption on zeolite and alumina supported rhodium, 2570-80 Tin oxide surfaces.Part 4. Infrared study of the adsorption of oxygen and carbon monoxide + oxygen mixtures on tin(1V) oxide, and the adsorption of carbon dioxide on ammonia-pretreated tin(1V) oxide, Tin oxide surfaces. Part 8. Infrared study of the mechanism of formation of a surface isocyanate species on tin oxide - 0.55 copper oxide during catalysis of the oxidation of carbon monoxide by nitric oxide, 2604-16 Tin oxide surfaces. Part 9. Infrared study of the adsorption of carbon monoxide, nitric oxide and their mixtures on tin(1V) oxide gels containing ion-exchanged chromium(III), manganese(II), iron(III), cobalt(II), nickel(I1) and copper(II), 2703-1 3 CALCIUM SULPHATE HEMIHYDRATE calcium sulphate hemihydrates, 1477-87 CAPILLARY DIFFUSION CARBON BLACK CARBON MONOXIDE 2597-603 CARBONYL SULPHIDE CARBONYLATION CARBOXYLATE Moderation of photochemically generated hot hydrogen atoms, 1687-92 Carbonylation of methanol and ethanol on a rhodium-zeolite catalyst, 23 13-19 Magneto-optical rotation studies of electrolyte solutions. Part 5.Measurements on aqueous solutions Electron transfer reactions involving chlorophylls a and b and carotenoids, 2760-2 Micellar catalysis of metal-complex formation. Kinetics of the reaction between nickel(I1) and pyridine- 2-azo-pdimethylaniline (PADA) in the presence of sodium dodecylsulphate micelles; a model system for the study of metal ion reactivity at charged interfaces, 10-21 Hydrogenolysis of cyclopentane and hydrogenation of benzene on palladium catalysts of widely varying dispersion, 174-8 1 Hydrogenation of acetylene over supported metal catalysts.Part 1. Adsorption of acetylene-14C and ethylene-14C on silica supported rhodium. iridium and palladium and alumina supported palladium, Acidic properties of mixed tin + antimony oxide catalysts, 20610 Influence of sodium on the physicochemical and catalytic properties of magnesium oxide, 250-6 1 Role of Broensted acid centres for alkene double bond migration over alumina at temperatures above Study of surface atom behaviour on platinum-silica and platinum-alumina catalysts by isotropic Reexamination of the diffuse reflectance spectra of copper/alumina catalysts, 758-61 Characterization of supported platinum, hydrogenation and hydrogendeuterium equilibration, 1064-74 Mechanism of ketonization of acetic acid on anatase Ti02 surfaces, 15 17-29 Dehydrogenation and isomerization of n-butenes on mixed tin + antimony oxide catalysts, 159&3 Structure and catalytic activity of cobalt magnesium alumina spinel solid solutions.Part 2. Decomposition of nitrous oxide, 1595-603 Semiconducting oxides: effects of electronic and surface structure on dissolution kinetics of nickel oxide, 161 5 2 3 Thermal reactions of methyl and acetyl manganese pentacarbonyls. Part 1. Initiation of free-radical polymerization and formation of methyl(2-methyl-4-oxopentanoate), 1634-47 Thermal reactions of perfluoromethyl and perfluoroacetyl manganese pentacarbonyls. Part 2. Initiation of free-radical polymerization and formation of methyl(2-methyl-4-ox0-5,5,5-trifluoropentanoate), Patterns of activity in the benzene-deuterium exchange reaction and the hydrogenation of benzene catalysed by evaporated metal films, 166C75 Polymerization of vinyl monomers initiated by chromium(I1) acetate + organic peroxides, 1726-37 of hydrophobic solutes, 960-3 CAROTENOID CATALYSIS 195-205 450 K, 498-505 exchange of oxygen from carbon dioxide, 506-8 1648-5412 J.C.S.FARADAY I SUBJECT INDEX VOL. 74 (1978) Living radical polymerizations of vinyl monomers initiated by aged chromium(I1) + BPO in homogeneous solution, 173849 Correlation of the catalytic activities of oxides with their work functions. Recombination of oxygen atoms on lithium(1 +) doped nickel oxides, 1750-7 Adsorption of hydrogen on a platinum-graphite catalyst.Part 1. Electron spin resonance measurement in the gas-solid system, 1963-72 Catalyst participation in the reduction of sulphur dioxide by carbon monoxide in the presence of water and oxygen, 198 1-9 Carbonylation of methanol and ethanol on a rhodium-zeolite catalyst, 23 13-19 Electron paramagnetic resonance study of molybdenum supported catalysts labelled with molybdenum- 95. Evidence for molybdenyl ions, 2378-84 Relation between propylene oxidation performance of copper-based bimetallic catalysts and the redox behaviour of their surfaces, 2490-500 Tin oxide surfaces. Part 8. Infrared study of the mechanism of formation of a surface isocyanate species on tin oxide - 0.55 copper oxide during catalysis of the oxidation of carbon monoxide by nitric oxide, 2604-16 Oxidation of sulphur dioxide in aerosol droplets, catalysed by manganous sulphate, 2689-702 Luminescence and other spectroscopic studies of the reaction of pyridine and oxygen with thermally Kinetics, thermochemistry and mechanism of hydrogenolysis of aliphatic aldehydes on nickel-silica, Preparation of high surface area reduced molybdenum oxide catalysts, 2982-90 Structural characterization of high surface area reduced molybdenum oxide catalysts, 299 1-9 Active centres on sodium hydrogen-Y zeolite in but-l-ene transformations, 146-52 Correlation of the catalytic activities of oxides with their work functions.Recombination of oxygen Chemical energy accommodation at catalyst surfaces. Flow reactor studies of the association of nitrogen Effect of lead compounds on heterogeneous oxidation catalysts, 1922-38 Correlation between results of X-ray photoelectron spectroscopic studies and catalytic behaviour of Relation between propylene oxidation performance of copper-based bimetallic catalysts and the redox Oxidation of sulphur dioxide in aerosol droplets, catalysed by manganous sulphate, 2689-702 Surface properties and catalytic activity of a molybdenum-fixed catalyst.Structure of the active site and activated strontium oxide, 2763-70 2873-84 CATALYST atoms on lithium(1 +) doped nickel oxides, 1750-7 atoms on metals at high temperatures, 1883-912 magnesium oxide, 2092- 100 behaviour of their surfaces, 2490-500 mechanism for selective oxidation of ethyl alcohol, 2968-8 1 CATION EXCHANGE Charge density effects in ion exchange.Part 2. Homovalent exchange equilibria, 1234-41 CATION EXCHANGER Stability of metal uncharged ligand complexes in ion exchangers. Part 3. Complex ion selectivity and Effect of molecular environment and of excitation energy on electron photoejection from Rate constants for the removal of radicals at the wall in linearly branched or terminated chain reactions, Moderated copolymerization. Part 2. Transfer constant of styryl radicals towards carbon tetrabromide: Charge density effects in ion exchange. Part 2. Homovalent exchange equilibria, 1234-41 Molecular interaction between iodine monochloride and diphenyl sulphides. A vibrational study, 5 19-24 Study by electron paramagnetic resonance of chargetransfer complexes formed by adsorption of TCNE X-ray photoelectron spectroscopy study of palladium and platinum ions in type Y-zeolite.Electron stepwise stability constants, 2470-80 monophenylphosphate, 1029-35 CESIUM CHAIN REACTION 765-75 CHAIN TRANSFER a penultimate unit effect in chain transfer, 1020-8 CHARGE DENSITY CHARGE TRANSFER on type X- and Y-zeolites, 530-7 transfer between metal aggregates and the support as evidenced by X-ray photoelectron spectroscopy and electron spin resonance, 440-9 CHARGE TRANSFER COMPLEXES CHARGE TRANSFER SPECTRA CHEMILUMINESCENCE Far-ultraviolet spectroscopy of chloride ion, 1776-85 Luminescence excitation and deexcitation involving one-electron transfer. Aqueous solutions of 1- aminonaphthalene+sodium)sulphonate, 2077-9 1 Effect of oxygen chemisorption and photodesorption on the conductivity of zinc oxide powder layers, 3 1-45 CHEMISORPTIONJ.C.S. FARADAY I SUBJECT INDEX VOL.74 (1978) 13 Hydrogen sorption by palladium-gold wires, 223-36 Sorption of hydrogen by palladium and palladium/silver alloy wires, 326-36 Infrared study of the adsorption of acetone on rutile, 403-17 Thermal stability and chemical reactivity of (Oz-)S species adsorbed on magnesium oxide surfaces, Electron spin resonance studies of the formation and thermal stability of oxygen radicals on calcium Temperature and pressure effects on surface processes at noble metal electrodes. Part 1. Entropy of Temperature and pressure effects on surface processes at noble metal electrodes. Part 2. Volume of Kinetics of activated chemisorption. Part 4. Differential heat of adsorption, 1507-16 Resonance Raman spectra of carbonium ions adsorbed on porous Vycor glass, 1562-8 y-Radiolysis of methane adsorbed on y-alumina. Part 2.Kinetics of reactions occurring during Sorption behaviour of silanated H-mordenite, 187 1-8 Infrared study of carbon monoxide chemisorption on zeolite and alumina supported rhodium, 2570-80 Tin oxide surfaces. Part 9. Infrared study of the adsorption of carbon monoxide, nitric oxide and their mixtures on tin(1V) oxide gels containing ion-exchanged chromium(III), manganese(II), iron(III), cobalt(II), nickel(I1) and copper(II), 2703-1 3 Infrared spectra of nitric oxide, nitrous oxide, nitrogen dioxide and oxygen adsorbed on silicon monoxide films. 2935-41 456-65 oxide and some other oxides, 883-92 chemisorption of hydrogen at platinum surfaces, 1373-89 adsorbed hydrogen and oxygen species at platinum and gold, 1390-402 irradiation, 1676-86 CHLORANIL 720-6 Temperature dependence of the low frequency dielectric dispersion in the perylene + chloranil complex, CHLORIDE CHLORINE Far-ultraviolet spectroscopy of chloride ion, 1776-85 Chlorine kinetic isotope effects, Thermal decomposition of l-chloroethane and evaluation of possible Rate of polymorphic transformation between phases I1 and I11 of hexachloroethane, 1913-21 Chlorine kinetic isotope effects. Thermal decomposition of l-chloroethane and evaluation of possible Comment on rate of polymorphic transformation between phases I1 and I11 of hexachloroethane, 2750-4 Energy distribution and mechanism in 3-chloro-3-methyldiazirine photolysis, 809-1 7 models of activated complex, 2714-23 CHLOROETHANE models of activated complex, 27 14-23 CHLOROMETHYLDIAZIRINE CHLOROMETHYLSILANE Adsorption of water vapour by silica and the effect of surface methylation, 1360-72 CHLOROPHYLL Electron transfer reactions involving chlorophylls a and b and carotenoids, 2760-2 Laser flash photolysis study of the photoionization of chlorpromazine and promazine in solution, Very low pressure pyrolysis (VLPP) of 3-chloropropionitrile, 91 2-1 8 Thermodynamics of adsorption based on gas-solid chromatography, 575-80 Gas-liquid chromatographic studies of thermodynamic interactions in ternary systems comprising Magnetic and optical studies of chromium oxides.Part 2. Calcination of chromic chloride supported on Van der Waals forces between objects covered with a chromium layer, 2637-51 Magnetic and optical studies of chromium oxides.Part 3. Calcination of coprecipitated chromium and Polymerization of vinyl monomers initiated by chromium(I1) acetate + organic peroxides, 1726-37 Living radical polymerizations of vinyl monomers initiated by aged chromium(I1) + BPO in Charge density effects in ion exchange. Part 2. Homovalent exchange equilibria, 1234-41 Magnetic and optical studies of chromium oxides. Part 3. Calcination of coprecipitated chromium and Fourier inversion of light scattering intensity data from coagulating dispersions, 11 12-24 Semiconducting oxides: effects of electronic and surface structure on dissolution kinetics of nickel oxide, CHLOROPROMAZINE 181 1-19 CH LOROPROPIONITRI LE CHROMATOG dinonylphthalate + trinitrotoluene + volatile hydrocarbon, 1655-65 alumina, 20 17-26 CHROMIUM aluminium hydroxide gels, 2807-17 CHROMIUM ACETATE homogeneous solution, 1738-49 CLAY CLUSTER COPPT aluminium hydroxide gels, 2807-1 7 COAGULATION COBALT14 J.C.S.FARADAY I SUBJECT INDEX VOL. 74 (1978) 1615-23 Spectroscopic investigation of the structure of a novel zerovalent cobalt nitrosyl in zeolite matrixes, Structure and catalytic activity of cobalt magnesium alumina spinel solid solutions. Part 2. Activity coefficients for the system hydrogen chloride + cobalt chloride + water at 298.15 K. Effects of Ring-disc electrodes. Part 18. Collection efficiency for high frequency a.c, 1007-19 Light scattering method for the study of close range structure in coagulating dispersions of equal sized Heterocoagulation.Part 3. Interactions of polyvinyl chloride latex with Ludox HS silica, 1346-59 Origin of charge on colloidal particles in butanol, 1583-9 Calculation of dispersion force interactions between colloidal particles in butan-l-ol,2008-16 Colloid stability in butanol, 2271-7 Transition metal ion exchange in zeolites. Part 3. Ternary exchange in mordenite involving ammonium, On the hydrolysis of silver(II), thallium(II), tin(III), and copper(III), 1820-6 Transport in aqueous solutions of Group IIB metal salts at 298.15 K. Part 6. Irreversible 3000-7 COBALT ALUMINATE Decomposition of nitrous oxide, 1595-603 higher-order electrostatic terms, 2037-44 COBALT CHLORIDE COLLECTION EFFICIENCY COLLOID spherical particles, 733-44 COMPLEX. triethanolammonium and complexed nickel(II), 745-55 COMPLEXING thermodynamic parameters for zinc chloride and verification of Onsager's reciprocal relationships, 2896-906 COMPRESSIBILITY pV-T studies on molten alkali nitrates.Part 1. Thermal pressure coefficients and compressibilities, Coupled fluxes in electrochemistry. Concentration distributions near electrodialysis membranes, Effect of pressure on the electrical conductivities of some molten B-group metal iodides and iodine, Velocity correlation coefficients as an expression of particle-particle interactions in (electrolyte) solutions Effects of water on proton migration in alcoholic solvents. Part. 5. Conductance of hydrogen chloride in On the hydrolysis of silver(II), thallium(II), tin(III), and copper(III), 1820-6 Viscosity and conductance studies in ethylene carbonate at 40°C, 2070-6 Light scattering method for the study of close range structure in coagulating dispersions of equal sized Moderated copolymerization.Part 2. Transfer constant of styryl radicals towards carbon tetrabromide: Influence of applied electric fields on the free radical copolymerization of methylmethacrylate and Stability of metal uncharged ligand complexes in ion exchangers. Part 2. The copper + ethylenediamine Adsorption of carbon monoxide on copper (100) studied by photoelectron spectroscopy and low energy Gamma radiolysis of copper(I1) nitrilotriacetate in aqueous solution, 622-35 Reexamination of the diffuse reflectance spectra of copper/alumina catalysts, 758-61 On the hydrolysis of silver(II), thallium(II), tin(III), and copper(III), 1820-6 Chemical and electrochemical kinetics of copper(I1) reduction in chloride media, 1973-80 Catalyst participation in the reduction of sulphur dioxide by carbon monoxide in the presence of water and oxygen, 198 1-9 Relation between propylene oxidation performance of copper-based bimetallic catalysts and the redox behaviour of their surfaces, 2490-500 Complexes of ammonia and ethylenediamine with copper(I1) on zeolite A, 2550-61 Tin oxide surfaces.Part 8. Infrared study of the mechanism of formation of a surface isocyanate species on tin oxide - 0.55 copper oxide during catalysis of the oxidation of carbon monoxide by nitric oxide, 2604 1 6 COPPER IONS 153-62 CONCN DISTRIBUTION 2839-49 COND 686-96 93347 methanol at 15,25 and 35°C and in ethanol and pentan-1-1 at 15 and 35"C, 1096-1 11 COORDINATION NUMBER spherical particles, 733-44 a penultimate unit effect in chain transfer, 1020-8 styrene.An unusual decomposition of benzoylperoxide, 1488-95 complex in montmorillonite and sulphonic acid resin, 182-9 electron diffraction, 546-54 COPOLYMERIZATION COPOLYMN COPPER Reactions of some simple a- and p-hydroxyalkyl radicals with cupric and cuprous ions in aqueousJ.C.S. FARADAY I SUBJECT INDEX VOL. 74 (1978) 15 solution. Radiation chemical study, 697-714 ion exchange, 13 1-5 CRYSTAL STRUCTURE Site group interaction effects in zeolite-Y. Part 1. Structural examination of the first stages of the silver Influence of sodium on the physicochemical and catalytic properties of magnesium oxide, 250-61 Luminescence of kyanoanthracene.Identification of new excimeric species, 1457-66 Study by electron paramagnetic resonance of charge-transfer complexes formed by adsorption of TCNE Cyclization in the gas phase photolysis of neopentyl bromide, 776-84 Thermodynamics of adsorption based on gas-solid chromatography, 575-80 Thermal unimolecular reactions of vinylcyclobutane and isopropenylcyclobutane, 1827-33 Intercrystalline molecular transport in zeolites studied by uptake experiments and by nuclear magnetic Gas phase pyrolysis of cyclopropene. Part 1. Kinetics and mechanism, 1 146-58 Allene isomerization, 1337-8 Pulse radiolysis study of protoferrihaem IX intercalated in sodium dodecyl sulphate micelles, 41 8-26 Analysis of pressure changes for simultaneous first-order decomposition reactions in a gas-kinetic Modified zeolites.Part 1. Dealuminated mordenites and their silanation, 2786-97 Modified zeolites. Part 2. Sorption by dealuminated, silanated mordenites, 2798-806 Theory of electrolytes. Part 3. On the number density of ions in the Debye-Hueckel ionic atmosphere, Analysis of pressure changes for simultaneous first-order decomposition reactions in a gas-kinetic Infrared spectra of nitric oxide, nitrous oxide, nitrogen dioxide and oxygen adsorbed on silicon Chemical processes at clean (l(r10) zinc oxide surfaces. Part 1. Thermal production of surface defects, Acidic properties of mixed tin + antimony oxide catalysts, 206-10 Location of cations in synthetic Zeolites-X and -Y.Part 5. The cation distribution in calcium-Y, Studies in the system calcium sulphate monohydrate. Part 6. Surface chemistry and porosity of the Correlation between results of X-ray photoelectron spectroscopic studies and catalytic behaviour of Influence of sodium on the physicochemical and catalytic properties of magnesium oxide, 250-6 1 Dehydrogenation and isomerization of n-butenes on mixed tin + antimony oxide catalysts, 1590-3 Fourier transform infrared spectroscopy of the zeolite NaH-Y + but-l-ene system, 2027-36 Correlation between results of X-ray photoelectron spectroscopic studies and catalytic behaviour of CUMENE CYANOANTHRACENE CYANOETHYLENE on type X- and Y-zeolites, 530-7 CY CLIZATION CYCLOALKANE CYCLOBUTANE CYCLOHEXANE resonance pulsed field gradient techniques, 12 10-20 CYCLOPROPENE CYTOCHROME C DEAD SPACE system with dead-space, 2755-9 DEALUMINATED MORDENITE DEBYE HUECKEL THEORY 2418-21 DECOMPN system with dead-space, 2755-9 monoxide films, 2935-41 2724-41 DEFECT DEHYDRATION calcium-X and lanthanum-Y in the ultimate stages of dehydration, 46676 calcium sulphate hemihydrates, 1477-87 magnesium oxide, 2092-100 DEHYDROGENATION magnesium oxide, 2092-1 00 DENSITY Partial molar volumes and viscosity of benzene solutions of tertiary n-alkylammonium picrates, 21 59-65 Rayleigh scattering depolarization ratio and the molecular polarizability anisotropy for gases, 3008-1 5 DEPOLARIZATION DESORPTION Effect of oxygen chemisorption and photodesorption on the conductivity of zinc oxide powder layers, Correlation between results of X-ray photoelectron spectroscopic studies and catalytic behaviour of Characterization of supported platinum, hydrogenation and hydrogen-cleuterium equilibration, 1064-74 Kinetic analysis of deuteron-transfer reactions of alkylamidines with (zH+I-nitrophenylnitromethane.31-45 magnesium oxide, 2092- 100 DEUTERIUM Implications of isotopic scrambling for the determination of kinetic isotope effects, 1254-6216 J.C.S. FARADAY I SUBJECT INDEX VOL. 74 (1978) DEUTERIUM EFFECT Kinetic isotope effects in the reactions of 4-nitrophenylnitromethane with alkylamidine bases in toluene, Kinetic isotope effect in the reaction of 4nitrophenylnitromethane with the cyclic amidine base DBU (1, Patterns of activity in the benzenAeuterium exchange reaction and the hydrogenation of benzene Thermodynamic study of deuterium exchange in water + methanol systems, 1768-75 Water42-water isotope effect on nuclear magnetic relaxation of alkali halide nuclei and preferential 1796-803 5-diazabicyclo( 5,4,0)undec-5-ene), 2065-9 catalysed by evaporated metal films, 1666-75 DEUTERIUM EXCHANGE DEUTERIUM ISOTOPE EFFECT solvation in mixed solvents.644-56 Kinetic isotope effect in the reaction of 4nitrophenylnitromethane with pentamethylguanidine in toluene, 1263-7 DI AZABICYCLOUNDECENE Kinetic isotope effect in the reaction of 4-nitrophenylnitromethane with the cyclic amidine base DBU (1, Kinetic isotope effect in the reaction of 4-nitrophenylnitromethane with the cyclic amidine base DBU (1, Energy distribution and mechanism in 3-chloro-3-methyldiazirine photolysis, 809-1 7 Temperature dependence of the low frequency dielectric dispersion in the perylene + chloranil complex, Relaxation processes of hydrogen bonded species in a polystyrene matrix, 2045-50 Kinetics of flowing dispersions.Part 1 1. Dielectric constants of streaming suspensions of spheroids, 5-diazabicyclo(5,4,0)undec-5-ene), 2065-9 5-diazabicyclo(5,4,0)undec-5-ene), 2065-9 DIAZABI 1YCLOUNDECENE DIAZIRINE DIELEC 720-6 DIELEC ABSORPTION DIELEC CONST 1242-53 Van der Waals forces between objects covered with a chromium layer, 2637-51 Dielectric properties of water adsorbed by kaolinite clays, 1221-33 Dielectric properties of N-methyl acetamide in carbon tetrachloride solution, 1 15-22 DIELEC LOSS DIELEC RELAXATION DIFFUSION Transport in aqueous solutions of Group IIB metal salts (298.15K).Part 3. Isotopic diffusion Diffusion in binary liquid mixtures of non electrolytes, 490-7 Flame photometric determinations of diffusion coefficients. Part 6. Results for carbon monoxide and coefficients for cadmium-115 ions in aqueous cadmium iodide, 93-102 free atoms of bromine, iodine, and thallium. 715-19 Velocity correlation coefficients as an expression of particle-particle interactions in (electrolyte) solutions 9-33-47 . - - . . Intercrystalline molecular transport in zeolites studied by uptake experiments and by nuclear magnetic resonance pulsed field gradient techniques, 12 10-20 Open-end capillary method in tracer and diffusion of electrolyte solutions, 2320-32 Model for analysing diffusion in zeolite crystals, 2423-33 Radiotracer studies of self-diffusion in the plastic solids norbornylene and norbornane, 2562-9 Transport in aqueous solutions of Group IIB metal salts (298.15 K).Part 4. Interpretation and Infrared study of the adsorption of diketones on silica immersed in carbon tetrachloride, 2 130-40 Radicals derived from 1,Misubstituted anthraquinones. Further evidence for association of quinones in Solvent effect on the dimerization and hydration constant of benzoic acid, 1467-76 Thermodynamics of hydrobromic acid in dioxan + water mixtures from electromotive force Ionic solvation in water + co-solvent mixtures. Part 6. Free energies of transfer of single ions from Dielectric properties of N-methyl acetamide in carbon tetrachloride solution, 1 15-22 Studies of reactions of atoms in a discharge flow stirred reactor.Part 3. The oxygen atom-dihydrogen- Studies of reactions of atoms in a discharge flow stirred reactor. Part 2. Oxygen atom + dihydrogen + DIFFUSION THEORY prediction of isotopic diffusion coefficients for cadmium in dilute solutions of cadmium iodide, 103-14 DIKETONE DIMERIZATION solution, 597-602 DIOXAN measurements at different temperatures, 22-30 water into water + dioxan mixtures, 1569-82 DIPOLE MOMENT DISCHARGE FLOW REACTION dioxygen system, 2672-7 DISCHARGE FLOW STIRRED REACTORJ.C.S. FARADAY I SUBJECT INDEX VOL. 74 (1978) 17 carbon monoxide system, 3 16-25 DISPERSION 720-6 Temperature dependence of the low frequency dielectric dispersion in the perylene + chloranil complex, Calculation of dispersion force interactions between colloidal particles in butan- l-o1,2Oo8-16 Van der Waals forces between objects covered with a chromium layer, 2637-51 Mutual reaction of isopropyl radicals, 3016-2 1 Mass spectrometric determination of the heats of formation of the silicon fluorides SiF(g), SiF2(g) and Kinetics and mechanism of fast metal-ligand substitution processes in aqueous and micellar solutions Electromotive force studies of electrolytic dissociation.Part 12. Dissociation constants of some strongly Ionic oxides: distinction between mechanisms and surface roughening effects in the dissolution of Washburn numbers. Part 3. Alkali-metal chlorides in the DMSO + water system; comparison with Some properties of binary aqueous liquid mixtures. Apparent molar volumes and heat capacities at 298. Ionic activities in sodium dodecyl sulphate solutions from electromotive force measurements, 1758-67 Reactions of n-butenes on palladium films.Evidence for n-allylic species, 2652-66 Measurement of forces between two mica surfaces in aqueous electrolyte solutions in the range 0-100 nm Sodium-23 quadrupole splittings in lyotropic liquid crystals. Relationship to electrical double layer Solid state reversible reactions. Thermal behaviour of the photoisomer of bi(anthracene9,lO- Aqueous solutions containing amino acids and peptides. Part 5 . Gibbs free energy of interaction of Transport in aqueous solutions of Group IIB metal salts at 298.15 K. Part 5. Irreversible DISPERSION FORCE DISPROPORTION ATION DISSOCN SiF&g), 1089-95 studied by means of a dyelaser photochemical relaxation technique, 2625-36 ionizing acids at zero ionic strength and 25"C, 1170-8 magnesium oxide, 2907-1 2 hydrochloric acid; structural effects, 380-92 15 K over the whole mole fraction range, 1 159-69 DISSOCN CONST DISSOLN DMSO DODECYL SODIUM SULPHATE DOUBLE BOND MIGRATION DOUBLE LAYER 975-1001 theory and estimates of double layer dimensions, 1290-300 dimethylene), 603-12 glycine with some alkali metal chlorides at 298.15 K, 2771-8 thermodynamic parameters for zinc perchlorate and verification of Onsager's reciprocal relationships, 2885-95 DTA ELEC ELEC COND Effect of pressure on the electrical conductivities of some molten B-group metal iodides and iodine, Protonic conductivity in layered tin chloride dihydrate single crystal, 2333-5 1 Electrical conductivities of shock-compressed solutions of potassium iodide in organic solvents, 2742-9 Hydration, dehydrative counter-ion binding and helix formation of charged poly(a-amino acid)s in Influence of applied electric fields on the free radical copolymerization of methylmethacrylate and Thermodynamics of hydrobromic acid in dioxan + water mixtures from electromotive force 686-96 ELEC CONDUCTANCE aqueous alcohol as revealed by a preferential binding study, 2583-96 styrene.An unusual decomposition of benzoylperoxide, 1488-95 measurements at different temDeratures. 22-30 ELEC FIELD EFFECT ELEC POTENTIAL ELECTROCHEM Electrochemical decomposition of biformylperoxide. A quantum mechanical calculation, 1496-9 Chemical and electrochemical kinetics of copper(I1) reduction in chloride media, 1973-80 ELECTRODE Ionic activities in sodium dodecyl sulphate solutions from electromotive force measurements, 1758-67 Electrical force between two permeable planar charged surfaces in an electrolyte solution, 261 7-24 Temperature and pressure effects on surface processes at noble metal electrodes.Part 1. Entropy of Temperature and pressure effects on surface processes at noble metal electrodes. Part 2. Volume of ELECTRODEPOSITION chemisorption of hydrogen at platinum surfaces, 1373-89 adsorbed hydrogen and oxygen species at platinum and gold, 1390-40218 J.C.S. FARADAY I SUBJECT INDEX VOL. 74 (1978) ELECTRODIALYSIS Coupled fluxes in electrochemistry. Concentration distributions near electrodialysis membranes, Polarization in electrodialysis.Rotating-disc studies, 2850-7 Surface and electrokinetic potentials of interfaces containing two types of ionizing group, 1 179-87 Origin of charge on colloidal particles in butanol, 1583-9 Self-diffusion coefficients of water in pure water and in aqueous solutions of several electrolytes with Colloid stability in butanol, 2271-7 Theory of electrolytes. Part 4. Model of polarizable dielectric spheres. Structure around ions in solution Theory of electrolytes. Part 3. On the number density of ions in the Debye-Hueckel ionic atmosphere, Polarization in electrodialysis. Rotating-disc studies, 2850-7 Open-end capillary method in tracer and diffusion of electrolyte solutions, 2320-32 Static relative permittivity of some electrolyte solutions in water and methanol, 2339-5 1 Model of polarisable spheres: a reappraisal, 756-7 X-ray photoelectron spectroscopy study of palladium and platinum ions in type Y-zeolite.Electron 2839-49 ELECTROKINETIC POTENTIAL ELECTROLYTE oxygen- I8 and deuterium as tracers, 1879-8 1 in relation to ionic solvation and activity coefficients, 2385-92 24 1 8-2 1 ELECTROLYTE SOLN ELECTROLYTE SOLUTION ELECTROLYTE THEORY ELECTRON EXCHANGE transfer between metal aggregates and the support as evidenced by X-ray photoelectron spectroscopy and electron spin resonance, 440-9 atom from measurements in flames, 53-62 paraquat radical analogues with oxygen, 665-75 Reversible pyridine-induced formation of superoxide ions labelled with oxygen-1 7, 1324-8 ELECTRON ION RECOMBINATION Kinetics of gas phase electron-ion recombination by nitrosyl + electron + nitrogen atom + oxygen Bipyridylium quaternary salts and related compounds. Part 6.Pulse radiolysis studies of the reaction of Electron transfer from aromatic molecules to dimethylmercury via a triplet exciplex, 827-36 Electron paramagnetic resonance study of electron transfer at the surface of alkaline earth oxides. Electron transfer reactions involving chlorophylls a and b and carotenoids, 2760-2 Origin of charge on colloidal particles in butanol, 1583--9 Calculations on ionic solvation. Part 2. Entropies of solvation of gaseous univalent ions using a one- Viscoelectric coefficient for water. 450-5 Ionic activities in sodium dodecyl sulphate solutions from electromotive force measurements, 1758-67 Kinetics of emulsion polymerization in the unsteady state, 3022-6 Thermodynamic study of deuterium exchange in water + methanol systems, 1768-75 Free energies and entropies of transfer of ions from water to methanol, ethanol and 1-propanol, 2101-10 Thermodynamic study of dilute aqueous solutions of organic compounds.Part 5. Open-chain saturated Heats of solution of electrolytes in ethanol and derived enthalpies of transfer from water, 359-65 Decomposition of 2,2,3,3-tetramethylbutane in the presence of oxygen, 366-79 Temperature and pressure effects on surface processes at noble metal electrodes. Part 1. Entropy of chemisorption of hydrogen at platinum surfaces, 1373-89 Free energies and entropies of transfer of ions from water to methanol, ethanol and 1-propanol, 2101-10 Thallous chloride-thallous sulphide phase diagram, 2 193-9 Thermodynamic study of dilute aqueous solutions of organic compounds.Part 5. Open-chain saturated Free energies and entropies of transfer of hydrogen halides from water to aqueous alcohols and the Study by electron paramagnetic resonance of chargetransfer complexes formed by adsorption of TCNE Electron paramagnetic resonance study of molybdenum supported catalysts labelled with molybdenum- ELECTRON TRANSFER ELECTROPHORESIS ELECTROSTATIC ENTROPY layer continuum model, 2858-67 ELECTROVISCOSITY EMF EMULSION POLYMN ENTHALPY bifunctional compounds, 2667-7 1 ENTHALPY TRANSFER ENTROPY bifunctional compounds, 2667-7 1 structure of aquo-organic solvents, 105 1-63 on type X- and Y-zeolites, 530-7 ENTROPY TRANSFER EPRJ.C.S.FARADAY I SUBJECT INDEX VOL. 74 (1978) 19 95. Evidence for molybdenyl ions, 2378-84 Complexes of ammonia and ethylenediamine with copper(I1) on zeolite A, 2550-61 pV-T studies on molten alkali nitrates. Part 2. Internal energies and equation of state, 163-73 X-ray photoelectron spectroscopy study of palladium and platinum ions in type Y-zeolite. Electron transfer between metal aggregates and the support as evidenced by X-ray photoelectron spectroscopy and electron spin resonance, 440-9 Adsorption of carbon monoxide on copper (100) studied by photoelectron spectroscopy and low energy electron diffraction, 546-54 Exchange processes in solutions of nitroxide surfactants, 220-2 X-ray photoelectron spectroscopy study of palladium and platinum ions in type Y-zeolite.Electron Thermal stability and chemical reactivity of (02~)s species adsorbed on magnesium oxide surfaces, In situ radiolysis electron spin resonance study of the radical-anions of substituted nitroimidazoles and Electron spin resonance studies of spin-labelled polymers. Part 14. End-group mobility of polystyrene Electron spin resonance studies of the formation and thermal stability of oxygen radicals on calcium Electron paramagnetic resonance study of electron transfer at the surface of alkaline earth oxides. 1 : 1 Hydrogen bonded complexes of phenol and 4fluorophenol with 2,2,6,6-tetramethylpiperidin-l- Characterization of the hydroxyls in offretite zeolite, 1786-95 Adsorption of hydrogen on a platinum-graphite catalyst.Part 1. Electron spin resonance measurement Magnetic and optical studies of chromium oxides. Part 2. Calcination of chromic chloride supported on Effect of viscosity on the bimolecular termination rate constants for semiquinone radicals in solution: a Mechanism of exchange in the manganese(I1)-ATP system from Fourier transform-nuclear magnetic Electron paramagnetic resonance study of molybdenum supported catalysts labelled with molybdenum- Kinetic electron spin resonance spectroscopy. Part 6. Formation and termination reactions of aliphatic Luminescence and other spectroscopic studies of the reaction of pyridine and oxygen with thermally Aqueous solutions containing amino acids and peptides. Part 5. Gibbs free energy of interaction of Magnetic and optical studies of chromium oxides.Part 3. Calcination of coprecipitated chromium and Spectroscopic investigation of the structure of a novel zerovalent cobalt nitrosyl in zeolite matrixes, Adsorption of ethane and ethylene by zeolites MgNaX and CaNaX with different degrees of ion Heats of solution of electrolytes in ethanol and derived enthalpies of transfer from water, 359-65 Free energies and entropies of transfer of hydrogen halides from water to aqueous alcohols and the Infrared studies of ethanol adsorbed on porous glass, 1945-52 Carbonylation of methanol and ethanol on a rhodium-zeolite catalyst, 23 13-19 Surface properties and catalytic activity of a molybdenum-fixed catalyst. Structure of the active site and mechanism for selective oxidation of ethyl alcohol, 2968-8 1 Kinetic analysis of deuteron-transfer reactions of alkylamidines with (2H+%-nitrophenylnitromethane.Implications of isotopic scrambling for the determination of kinetic isotope effects, 1254-62 Hydrogenation of acetylene over supported metal catalysts. Part 1. Adsorption of acetylene-l4C and ethylene-14C on silica supported rhodium, iridium and palladium and alumina supported palladium, Adsorption of ethane and ethylene by zeolites MgNaX and CaNaX with different degrees of ion exchange, 306-1 5 Hydrogenation of acetylene over supported metal catalysts. Part 2. Carbon-14 tracer study of EQUATION OF STATE ESCA ESR transfer between metal aggregates and the support as evidenced by X-ray photoelectron spectroscopy and electron spin resonance, 440-9 456-65 nitroaromatic compounds, 51 1-18 as a function of temperature and solvent, 727-32 oxide and some other oxides, 883-92 Reversible pyridine-induced formation of superoxide ions labelled with oxygen-1 7, 1324-8 oxyl: an electron spin resonance study, 155661 in the gas-solid system, 1963-72 alumina, 20 17-26 kinetic ESR study, 21 11-20 resonance and electron paramagnetic resonance data, 21 54-8 95.Evidence for molybdenyl ions, 2378-84 radicals by reductive dissociation of halogen~ompounds, 248 1-9 activated strontium oxide, 2763-70 glycine with some alkali metal chlorides at 298.15 K, 2771-8 aluminium hydroxide gels, 2807- 17 3000-7 ETHANE exchange, 306-1 5 ETHANOL structure of aquo-organic solvents, 105 1-63 ETHYLBUTYLAMIDINE ETHYLENE 195-20520 J.C.S. FARADAY I SUBJECT INDEX VOL.74 (1978) deactivation phenomena, 657-64 solution. Radiation chemical study, 697-7 14 Reactions of some simple a- and j3-hydroxyalkyl radicals with cupric and cuprous ions in aqueous Shock tube studies of the high temperature pyrolysis of acetylene and ethylene, 1.403-9 Viscosity and conductance studies in ethylene carbonate at 40°C, 2070-6 Stability of metal uncharged ligand complexes in ion exchangers. Part 2. The copper + ethylenediamine Kinetics of quaternization of &methyl and 4ethyl pyridine with n-propyl and n-butyl bromide in ETHYLENE CARBONATE ETHYLENEDIAMINE complex in montmorillonite and sulphonic acid resin, 182-9 sulpholane, 427-3 1 ETHYLPY RIDINE EVA€" HEAT Vapour pressure measurements on some organic high explosives, 1339-45 EXCHANGE Transition metal ion exchange in zeolites.Part 3. Ternary exchange in mordenite involving ammonium, Reactions of n-butenes on palladium films. Evidence for n-allylic species, 2652-66 Luminescence of kyanoanthracene. Identification of new excimeric species, 1457-66 Electron transfer from aromatic molecules to dimethylmercury via a triplet exciplex, 827-36 Photoluminescent spectra of surface states in alkaline earth oxides, 291 3-22 Vapour pressure measurements on some organic high explosives, 1339-45 Far-ultraviolet spectroscopy of chloride ion, 1776-85 Heats of hydrogenation of large molecules. Part 2. Six unsaturated and polyunsaturated fatty acids, Patterns of activity in the benzenedeuterium exchange reaction and the hydrogenation of benzene catalysed by evaporated metal films, 1666-75 Flow equation for coagulated suspensions, 785-94 Surface properties and catalytic activity of a molybdenum-fixed catalyst. Structure of the active site and Kinetics of gas phase electron-ion recombination by nitrosyl + electron + nitrogen atom + oxygen Kinetics of gas phase ion-ion recombination in nitrosyl + X- + nitric oxide + X for X being chlorine, Flame Dhotometric determinations of diffusion coefficients.Part 6. Results for carbon monoxide and triethanolammonium and complexed nickel(II), 745-55 EXCIMER EXCIPLEX EXCITON EXPLOSIVE FAR UV FATTY ACID 46-52 FERMI LEVEL FERRIC OXIDE FIXATION mechanism for selective oxidation of ethyl alcohol, 2968-8 1 atom from measurements in flames, 53-62 bromine and iodine, 63-70 FLAME free atoms of bromine, iodine, and thallium, 7 15-19 FLOC STRUCTURE Light scattering method for the study of close range structure in coagulating dispersions of equal sized Reversible flocculation of sterically-stabilized dispersions, 337-47 Light scattering method for the study of close range structure in coagulating dispersions of equal sized Colloid stability in butanol, 2271-7 Capillary Phenomena. Part 6.Behaviour associated with the flotation and mechanical manipulation of Capillary Phenomena. Part 6. Behaviour associated with the flotation and mechanical manipulation of Rapidly converging activity expansions for representing the thermodynamic properties of fluid systems: Electron transfer from aromatic molecules to dimethylmercury via a triplet exciplex, 827-36 Effect of molecular environment and of excitation energy on electron photoejection from Carbon difluoride emission during vacuum ultraviolet photodissociation of dibromodifluoromethane, spherical particles, 733-44 FLOCCULATION spherical particles, 733-44 FLOTATION solid spheres at fluid interfaces, 846-57 solid spheres at fluid interfaces, 846-57 gases, nonelectrolyte solutions, weak and strong electrolyte solutions, 1301-23 FLUID INTERFACE FLUID SYSTEM FLUORESCENCE monophenylphosphate, 1029-35 2930-4J.C.S.FARADAY I SUBJECT INDEX VOL. 74 (1978) 21 FLUORESCENCE QUENCHING FLUORIDE Luminescence excitation and de-excitation involving one-electron transfer. Aqueous solutions of 1- Application of polymer theory to silicate melts. The system metal(I1) oxide + metal(I1) fluoride + silica, Moderation of photochemically generated hot hydrogen atoms, 1687-92 Thermodynamics and constitution of silicate melts.The system lead monoxide + lead difluoride + Coupled fluxes in electrochemistry. Concentration distributions near electrodialysis membranes, Some properties of binary aqueous liquid mixtures. Apparent molar volumes and heat capacities at 298. Fragmentation and isomerization of protonated 3-methylbut-l-ene ions in gas-phase radiolysis, Free energies and entropies of transfer of ions from water to methanol, ethanol and 1-propanol, 2101-10 Thallous chloride-thallous sulphide phase diagram, 2 1939 Thermodynamic study of dilute aqueous solutions of organic compounds. Part 5. Open-chain saturated Aqueous solutions containing amino acids and peptides.Part 5. Gibbs free energy of interaction of Calculations on ionic solvation. Part 1. Free energies of solvation of gaseous univalent ions using a one- Aqueous solutions containing amino acids and peptides. Part 8. Gibbs free energy of interaction of Ionic solvation in water + co-solvent mixtures. Part 5. Free energies of transfer of large single ions Free energies and entropies of transfer of hydrogen halides from water to aqueous alcohols and the Ionic solvation in water + co-solvent mixtures. Part 6. Free energies of transfer of single ions from Rate constants for the removal of radicals at the wall in linearly branched or terminated chain reactions, Freezing points of aqueous alcohols. Free energy of interaction of the CHOH, CH2, CONH and C = C Freezing points of aqueous alcohols.Free energy of interaction of the CHOH, CH2, CONH and C = C Transference numbers of a 2:2 electrolyte: magnesium sulphate in water at 25" C, 103644 Effects of water on proton migration in alcoholic solvents. Part. 5. Conductance of hydrogen chloride in methanol at 15,25 and 35°C and in ethanol and pentan-1-1 at 15 and 35"C, 1096-1 11 Gas-liquid chromatographic studies of thermodynamic interactions in ternary systems comprising dinonylphthalate + trinitrotoluene + volatile hydrocarbon, 1655-65 Thermodynamics of adsorption based on gas-solid chromatography, 575-80 Tin oxide surfaces. Part 9. Infrared study of the adsorption of carbon monoxide, nitric oxide and their mixtures on tin(1V) oxide gels containing ion-exchanged chromium(III), manganese(II), iron(III), cobalt(II), nickel(I1) and copper(II), 2703-1 3 aminonaphthalene4--(sodium)sulphonate, 2077-9 1 2942-5 1 FLUOROALKANE FLUOROSILICATE silica, 2952-67 283949 FORMAMIDE FLUX COUPLING 15 K over the whole mole fraction range, 1 159-69 1939-44 FREE ENERGY FRAGMENTATION bifunctional compounds, 2667-71 glycine with some alkali metal chlorides at 298.15 K, 2771-8 layer continuum model, 1604-14 some a,o-amino acids with sodium chloride at 298.15 K, 2779-85 from water into water + methanol with the neutral component removed, 636-43 structure of aquo-arganic solvents, 1051-63 water into water + dioxan mixtures, 1569-82 765-75 FREE ENERGY CALCN FREE ENERGY INTERACTION FREE ENERGY TRANSFER FREE RADICAL FREEZING POINTS functional groups in dilute aqueous solutions, 1990-2007 functional groups in dilute aqueous solutions, 1990-2007 FUNCTIONAL GROUP INTERACTION FUOSS ONSAGER THEORY GAS LIQ CHROMATOG GAS SOLID CHROMATOGRAPHY GEL GLASS Surface and electrokinetic potentials of interfaces containing two types of ionizing group, 1179-87 Infrared studies of ethanol adsorbed on porous glass, 1945-52 Aqueous solutions containing amino acids and peptides.Part 5. Gibbs free energy of interaction of glycine with some alkali metal chlorides at 298.15 K, 2771-8 GLYCINE22 J.C.S. FARADAY I SUBJECT INDEX VOL. 74 (1978) GOLD Hydrogen sorption by palladium-gold wires, 223-36 Temperature and pressure effects on surface processes at noble metal electrodes. Part 2. Volume of Relation between propylene oxidation performance of copper-based bimetallic catalysts and the redox Adsorption of hydrogen on a platinum-graphite catalyst.Part 1. Electron spin resonance measurement Adsorption of gas mixtures of 2,24imethylpropane and n-butane on graphite and application of ideal Calculation of dispersion force interactions between colloidal particles in butan-1-01, 2008-1 6 Freezing points of aqueous alcohols. Free energy of interaction of the CHOH, CH2, CONH and C=C Effect of pressure on the electrical conductivities of some molten B-group metal iodides and iodine, Kinetic isotope effect in the reaction of 4nitrophenylnitromethane with pentamethylguanidine in Pulse radiolysis study of protoferrihaem IX intercalated in sodium dodecyl sulphate micelles, 41 8-26 Infrared studies of halide ion solvation in methanol, 2146-53 Kinetic electron spin resonance spectroscopy.Part 6. Formation and termination reactions of aliphatic Adsorption of ethane and ethylene by zeolites MgNaX and CaNaX with different degrees of ion Sorption of hydrogen by palladium and palladium/silver alloy wires, 326-36 Kinetics of activated chemisorption. Part 4. Differential heat of adsorption, 1507-16 Some properties of binary aqueous liquid mixtures. Apparent molar volumes and heat capacities at 298. Heat capacities of hydration of saturated uncharged organic compounds at 25"C, 2408-1 7 Mass spectrometric determination of the heats of formation of the silicon fluorides SiF(g), SiF2(g) and Thallous chloride-thallous sulphide phase diagram, 2 193-9 Thermodynamic study of dilute aqueous solutions of organic compounds.Part 5. Open-chain saturated Heats of hydrogenation of large molecules. Part 2. Six unsaturated and polyunsaturated fatty acids, Heats of hydrogenation of large molecules. Part 3. Five simple unsaturated triglycerides Heats of mixing and the solid-state transition in ( ( C ~ H S ) ~ P C ~ I ~ ) ~ - ~ +((C~HS)~ASCH~)~ +(TCNQ)2-- Heats of solution of electrolytes in ethanol and derived enthalpies of transfer from water, 359-65 On the hydrolysis of silver(II), thallium(II), tin(III), and copper(III), 1820-6 Charge density effects in ion exchange. Part 2. Homovalent exchange equilibria, 1234-41 Solubility of helium and hydrogen in some water + alcohol systems, 1444-56 Bipyridylium quaternary salts and related compounds. Part 6.Pulse radiolysis studies of the reaction of Comment on rate of polymorphic transformation between phases I1 and I11 of hexachloroethane, 2750-4 adsorbed hydrogen and oxygen species at platinum and gold, 1390-402 behaviour of their surfaces, 2490-500 in the gas-solid system, 1963-72 adsorbed solution theory, 2265-70 GRAPHITE GRAPHON GROUP functional groups in dilute aqueous solutions, 1990-2007 686-96 GUANIDINE GROUP IIIA toluene, 1263-7 HAEMIN HALIDE HALOGENOCARBOXYLIC ACID radicals by reductive dissociation of halogeno-compounds, 248 1-9 exchange, 306-1 5 HEAT ADSORPTION HEAT CAPACITY 15 K over the whole mole fraction range, 1 159-69 HEAT FORMATION SiF3(g), 1089-95 HEAT FUSION HEAT HYDRATION bifunctional compounds, 2667-7 1 46-52 (triacylglycerols), 2868-72 (0 HEAT HYDROGENATION HEAT MIXING x 5 l), anion radical salts, 1 9 W HEAT SOLN HEAVY METAL OXIDN HECTORITE HELIUM HERBICIDE paraquat radical analogues with oxygen, 665-75 HEXACHLOROETHANEJ.C.S.FARADAY I-SUBJECT INDEX VOL. 74 (1978) 23 HEXANE Intercrystalline molecular transport in zeolites studied by uptake experiments and by nuclear magnetic Ring-disc electrodes. Part 18. Collection efficiency for high frequency a.c, 1007-19 pH calibration of tetroxalate, tartrate and phthalate buffer solutions at above 100°C, 2434-51 Interaction of water molecules with the surface of tin(1v) oxide, 676-85 Recoil tritium reactions with methylsilane43: pressure dependent yields, 8 18-26 Solid state reactions of radio subhur in silver-doDed Dotassium chloride, 2452-9 resonance pulsed field gradient techniques, 1210-20 HIGH FREQUENCY AC HIGH TEMP HILL DE BOER EQUATION HOT ATOM HOT ATOM REACTION I I HYDRATION Solvent effect on the dimerization and hydration constant of benzoic acid, 1467-76 Heat capacities of hydration of saturated uncharged organic compounds at 25"C, 2408-1 7 Low temperature infrared spectroscopic study of the solvation of ions in water, 251 8-29 Hydration, dehydrative counter-ion binding and helix formation of charged poly(a-amino acid)s in Thermodynamics of hydrobromic acid in dioxan + water mixtures from electromotive force Photooxidation of floating hydrocarbon oils in the presence of some naphthalene derivatives, 123-30 Rayleigh scattering depolarization ratio and the molecular polarizability anisotropy for gases, 3008-1 5 Temperature and pressure effects on surface processes at noble metal electrodes. Part 1.Entropy of chemisorption of hydrogen at platinum surfaces, 1373-89 Temperature and pressure effects on surface processes at noble metal electrodes. Part 2. Volume of adsorbed hydrogen and oxygen species at platinum and gold, 1390-402 Solubility of helium and hydrogen in some water + alcohol systems, 1444-56 Studies of reactions of atoms in a discharge flow stirred reactor. Part 3. The oxygen atom-dihydrogen- dioxygen system, 2672-7 Studies of reactions of atoms in a discharge flow stirred reactor. Part 2. Oxygen atom + dihydrogen + carbon monoxide system, 3 1625 Reactions of presolvated electrons and hydrogen atoms with benzyl chloride in methanol. A pulse radiolysis study, 964-74 Moderation of photochemically generated hot hydrogen atoms, 1687-92 Structure of aqueous solutions.Infrared librational band study of structufe making and structure Infrared study of the adsorption of anisoles on silica immersed in heptane, 1 125-36 Infrared study of the adsorption of phenols on silica immersed in heptane, 1137-45 1 : 1 Hydrogen bonded complexes of phenol and 4-fluorophenol with 2,2,6,6-tetramethylpiperidin-1- Infrared study of the adsorption of diketones on silica immersed in carbon tetrachloride, 21 30-40 Low temperature infrared spectroscopic study of the solvation of ions in water, 2518-29 Thermodynamics of binary liquid mixtures involving hydrogen bromide, hydrogen chloride and xenon, Thermodynamics of binary liquid mixtures involving hydrogen bromide, hydrogen chloride and xenon, Effects of water on proton migration in alcoholic solvents.Part. 5. Conductance of hydrogen chloride in Activity coefficients for the system hydrogen chloride + cobalt chloride + water at 298.15 K. Effects of Infrared study of the adsorption of acetone on rutile, 403-17 Characterization of supported platinum, hydrogenation and hydrogen-deuterium equilibration, 1064-74 Free energies and entropies of transfer of hydrogen halides from water to aqueous alcohols and the aqueous alcohol as revealed by a preferential binding study, 2583-96 measurements at different temperatures, 22-30 HYDROBROMIC ACID HYDROCARBON HYDROGEN HYDROGEN ATOM HYDROGEN BOND breaking by dissolved electrolytes, 583-96 oxyl: an electron spin resonance study, 1556-61 HYDROGEN BROMIDE 893-9 1 1 HYDROGEN CHLORIDE 893-91 1 methanol at 15,25 and 35°C and in ethanol and pentan-1-01 at 15 and 35"C, 1096-1 11 higher-order electrostatic terms, 2037-44 HYDROGEN EXCHANGE HYDROGEN HALIDE structure of aquo-organic solvents, 105 1-63 HYDROGEN MORDENITE Modified zeolites.Part 1. Dealuminated mordenites and their silanation, 2786-97 HYDROGEN PEROXIDE Environmental control of reactions: influence of poly(L-glutamate) on the kinetics of decomposition of hydrogen peroxide catalyzed by quaterpyridineiron (111) complex ions, 288-9624 J.C.S. FARADAY I SUBJECT INDEX VOL. 74 (1978) HYDROGEN REDN Kinetics of the decomposition and hydrogen reduction of nitric oxide on niobium, nickel and platinum filaments at high temperatures and low pressures, 21 1-19 Heats of hydrogenation of large molecules.Part 2. Six unsaturated and polyunsaturated fatty acids, 46-52 Hydrogenolysis of cyclopentane and hydrogenation of benzene on palladium catalysts of widely varying dispersion, 174-8 1 Hydrogenation of acetylene over supported metal catalysts. Part 1. Adsorption of acetylene-14C and ethylene-14C on silica supported rhodium, indium and palladium and alumina supported palladium, Hydrogenation of acetylene over supported metal catalysts. Part 2. Carbon-14 tracer study of deactivation phenomena, 657-64 Characterization of supported platinum, hydrogenation and hydrogen-cleuterium equilibration, 1064-74 Patterns of activity in the benzendeuterium exchange reaction and the hydrogenation of benzene catalysed by evaporated metal films, 1666-75 Reactions of propyne and propadiene on magnesium films.Part 1. Self-hydrogenation, 2678-88 Kinetics, thermochemistry and mechanism of hydrogenolysis of aliphatic aldehydes on nickel-silica, Solubility equilibrium of silver(1) oxide in molten lithium nitrate + potassium nitrate mixtures, 1-9 Effect of polyelectrolytes on the kinetics of ionic reactions. Part 5. Decomposition of 2,4- On the hydrolysis of silver(II), thallium(II), tin(III), and copper(III), 1820-6 Polymerization of vinyl monomers initiated by chromium(I1) acetate + organic peroxides, 1726-37 Magnet-ptical rotation studies of electrolyte solutions. Part 5. Measurements on aqueous solutions Magnetic and optical studies of chromium oxides.Part 3. Calcination of coprecipitated chromium and Reactions of some simple a- and B-hydroxyalkyl radicals with cupric and cuprous ions in aqueous Partial molar volumes of organic compounds in water. Part 4. Aminocarboxylic acids, 858-68 Reactions of some simple a- and fl-hydroxyalkyl radicals with cupric and cuprous ions in aqueous Reactions of some simple a- and 8-hydroxyalkyl radicals with cupric and cuprous ions in aqueous On the hydrolysis of silver(II), thallium(II), tin(III), and copper(III), 1820-6 Freezing points of aqueous alcohols. Free energy of interaction of the CHOH, CH2, CONH and C =C Low temperature infrared spectroscopic study of the solvation of ions in water, 2518-29 Freezing points of aqueous alcohols. Free energy of interaction of the CHOH, CH2, CONH and C = C Aqueous solutions containing amino acids and peptides.Part 5. Gibbs free energy of interaction of Capillary Phenomena. Part 6. Behaviour associated with the flotation and mechanical manipulation of Measurement of forces between two mica surfaces in aqueous electrolyte solutions in the range 0-100 nm Surface and electrokinetic potentials of interfaces containing two types of ionizing group, 1179-87 Shape of a meniscus in a rotating vertical tube, 555-74 p-V-T studies on molten alkali nitrates. Part 2. Internal energies and equation of state, 163-73 Rotational barriers in N,N-dimethylbiuret. Experimental and theoretical studies, 1002-6 HYDROGENATION 195-205 HYDROGENOLYSIS 2873-84 HYDROLYSIS dinitrophenylphosphate in polycation solutions, 1 196209 HYDROPEROXIDE HYDROPHOBIC ELECTROLYTE of hydrophobic solutes, 960-3 aluminium hydroxide gels, 2807- 17 solution.Radiation chemical study, 697-714 HYDROXIDE HYDROXYALKYL HYDROXYALKYL AMIDE HYDROXYALKYL RADICAL solution. Radiation chemical study, 697-7 14 solution. Radiation chemical study, 697-7 14 HYDROXYETHYL HYDROXYL HYDROXYMETHY L functional groups in dilute aqueous solutions, 1990-2007 ICE INTERACTION functional groups in dilute aqueous solutions, 1990-2007 glycine with some alkali metal chlorides at 298.15 K, 2771-8 solid spheres at fluid interfaces, 846-57 INTERFACE 975- 1 00 1 INTERFACIAL TENSION INTERNAL PRESSURE INTERNAL ROTATIONJ.C.S. FARADAY I SUBJECT INDEX VOL. 74 (1978) 25 INTERSYSTEM CROSSING Mercury(63Pl) photosensitization of 3-methylbut-l-ene. Part 2.Intersystem crossing and cyclization Electron transfer from aromatic molecules to dimethylmercury via a triplet exciplex, 827-36 Effect of pressure on the electrical conductivities of some molten B-group metal iodides and iodine, Flame uhotometric determinations of diffusion coefficients. Part 6. Results for carbon monoxide and of the 2-methylbuta-l,34iyl biradical, 277-87 IODINE 686-96 free atoms of bromine, iodine, and thallium, 7 15-19 IODINE CHLORIDE TON Molecular interaction between iodine monochloride and diphenyl sulphides. A vibrational study, 5 19-24 _ _ _ Viscosity and conductance studies in ethylene carbonate at 40°C, 2070-6 Theory of electrolytes. Part 4. Model of polarizable dielectric spheres. Structure around ions in solution Calculations on ionic solvation.Part 2. Entropies of solvation of gaseous univalent ions using a one- Ionic activities in sodium dodecyl sulphate solutions from electromotive force measurements, 175867 Coupled fluxes in electrochemistry. Concentration distributions near electrodialysis membranes, Site group interaction effects in zeolite-". Part 1. Structural examination of the first stages of the silver Site group interaction effects in zeolite-Y. Part 2. Sodium-silver selectivity in different site groups, Stability of metal uncharged ligand complexes in ion exchangers. Part 2. The copper + ethylenediamine Transition metal ion exchange in zeolites. Part 3. Ternary exchange in mordenite involving ammonium, Thermal ion-molecule reactions in oxygen-containing molecules.Proton and hydride ion transfer Kinetics of gas phase electron-ion recombination by nitrosyl + electron -+ nitrogen atom + oxygen Kinetics of gas phase ion-ion recombination in nitrosyl + X- + nitric oxide + X for X being chlorine, Calculations on ionic solvation. Part 1. Free energies of solvation of gaseous univalent ions using a one- Low temperature infrared spectroscopic study of the solvation of ions in water, 2518-29 Nature of solutions of water in sulphuric acid, 2179-92 Molecular interaction between iodine monochloride and diphenyl sulphides. A vibrational study, 5 19-24 Absorption spectra of radical ions of polyenones of biological interest, 538-45 Structure of aqueous solutions. Infrared librational band study of structure making and structure Infrared study of the adsorption of anisoles on silica immersed in heptane, 1125-36 Infrared study of the adsorption of phenols on silica immersed in heptane, 11 37-45 Electronic absorption spectra of benzoyl radicals produced from benzoyl halides by irradiation with y- Adsorption of water vapour by silica and the effect of surface methylation, 1360-72 Semiconducting oxides: infrared and rate studies of the effects of surface blocking by surfactants in Characterization of the hydroxyls in offretite zeolite, 1786-95 Infrared studies of ethanol adsorbed on porous glass, 1945-52 Fourier transform infrared spectroscopy of the zeolite NaH-Y + but-l-ene system, 2027-36 Infrared study of the adsorption of diketones on silica immersed in carbon tetrachloride, 21 30-40 Infrared study of the adsorption of linoleic acid on alumina immersed in carbon tetrachloride, 2141-5 Infrared studies of halide ion solvation in methanol, 2146-53 Infrared study of adsorption on silica from two-component and three-component liquid mixtures, Low temperature infrared spectroscopic study of the solvation of ions in water, 251 8-29 Complexes of ammonia and ethylenediamine with copper(I1) on zeolite A, 2550-61 Infrared study of carbon monoxide chemisorption on zeolite and alumina supported rhodium, 2570-80 in relation to ionic solvation and activity coefficients, 2385-92 layer continuum model, 2858-67 ION ACTIVITY ION DISTRIBUTION 2839-49 ION EXCHANGE ion exchange, 13 1-5 136-45 complex in montmorillonite and sulphonic acid resin, 182-9 triethanolammonium and complexed nickel(II), 745-55 reactions in acetaldehyde, 195342 atom from measurements in flames, 53-62 bromine and iodine, 63-70 layer continuum model, 1604-14 ION MOLECULE REACTION ION RECOMBINATION ION SOLVATION IONIC SOLVATION IONIZATION IR breaking by dissolved electrolytes, 583-96 rays in organic glass, 1 188-95 dissolution kinetics, 1624-33 2393-40726 J.C.S.FARADAY I SUBJECT INDEX VOL. 74 (1978) Tin oxiuc surfaces. Part 4. Infrared study of the adsorption of oxygen and carbon monoxide + oxygen mixtures on tin(1V) oxide, and the adsorption of carbon dioxide on ammonia-pretreated tin(1V) oxide, Tin oxide surfaces. Part 8. Infrared study of the mechanism of formation of a surface isocyanate species on tin oxide - 0.55 copper oxide during catalysis of the oxidation of carbon monoxide by nitric oxide, 2604- 1 6 Infrared spectra of nitric oxide, nitrous oxide, nitrogen dioxide and oxygen adsorbed on silicon monoxide films, 2935-41 Surface properties and catalytic activity of a molybdenum-fixed catalyst.Structure of the active site and mechanism for selective oxidation of ethyl alcohol, 2968-8 1 Spectroscopic investigation of the structure of a novel zerovalent cobalt nitrosyl in zeolite matrixes, 3000-7 Hydrogenation of acetylene over supported metal catalysts. Part 1. Adsorption of acetylene-14C and ethylene-14C on silica supported rhodium, iridium and palladium and alumina supported palladium, Hydrogenation of acetylene over supported metal catalysts. Part 2. Carbon-14 tracer study of deactivation phenomena, 657-64 Examination of activation parameters for the dissociation of iron(II1) complexes as a means of assessing mechanistic ambiguities. Data for phenolic complexes, 525-9 Spectrophotometric investigations of aqueous solutions at elevated temperatures.Effect 6f temperature on the stability constants of the tris complexes of 1, 10-phenanthroline, 5-nitrc~1,IO-phenanthroline and 2,2'-bipyridyl with iron (11), 1081-8 thermodynamic parameters for zinc chloride and verification of Onsager's reciprocal relationships, 2896-906 2597-603 IRIDIUM 195-205 IRON IRREVERSIBLE THERMODN Transport in aqueous solutions of Group IIB metal salts at 298.15 K. Part 6. Irreversible IRREVERSIBLE THERMODYNAMICS Transport in aqueous solutions of Group IIB metal salts (298.15K). Part 3. Isotopic diffusion Transport in aqueous solutions of Group IIB metal salts (298.15 K).Part 4. Interpretation and Addition of i-butane to slowly reacting mixtures of hydrogen and oxygen at 480°C, 2229-51 p-V-T studies on molten alkali nitrates. Part 1. Thermal pressure coefficients and compressibilities, Tin oxide surfaces. Part 8. Infrared study of the mechanism of formation of a surface isocyanate species on tin oxide - 0.55 copper oxide dunng catalysis of the oxidation of carbon monoxide by nitric oxide, 2604- 1 6 coefficients for cadmium-1 15 ions in aqueous cadmium iodide, 93-102 prediction of isotopic diffusion coefficients for cadmium in dilute solutlons of cadmium iodide, 103-14 ISOBUTANE ISOCHORE 153-62 ISOCYANATE ISOMERIZATION Acidic properties of mixed tin + antimony oxide catalysts, 206-10 Influence of sodium on the physicochemical and catalytic properties of magnesium oxide, 250-61 Role of Broensted acid centres for alkene double bond migration over alumina at temperatures above Solid state reversible reactions.Thermal behaviour of the photoisomer of bi(anthracene-9,IO- Gas phase pyrolysis of cyclopropene. Part 1. Kinetics and mechanism, 1 146-58 Allene isomerization, 1337-8 Isomerization of n-butenes on A-type zeolites studied by infrared spectroscopy. Part 1. n-Butene adsorption on zeolites containing alkali and alkaline earth cations, 1435-43 Dehydrogenation and isomerization of n-butenes on mixed tin + antimony oxide catalysts, 1590-3 Fragmentation and isomerization of protonated 3-methylbut-l-ene ions in gas-phase radiolysis, 1939-44 Fourier transform infrared spectroscopy of the zeolite NaH-Y + but-lhne system, 2027-36 Reactions of n-butenes on palladium films.Evidence for n-allylic species, 2652-66 Mutual reaction of isopropyl radicals, 301 6-21 Self-reactions of isopropylperoxy radicals in the gas phase, 2293-300 Adsorption of butane-l,4-diol at the mercury-aqueous solution interface. Transition with polarization Investigation of the surface heterogeneity of maximally hydroxylated nonporous silica by gas adsorption, Kinetic analysis of deuteron-transfer reactions of alkylamidines with (2H2)-4-nitrophenylnitromethane. 450 K, 498-505 dimethylene), 603- 12 ISOPROPYL RADICAL ISOPROPYLPEROXY RADICAL ISOTHERM between two ideal adsorption models, 79-92 1045-9 ISOTOPE EFFECTJ.C.S.FARADAY I SUBJECT INDEX VOL. 74 (1978) 27 Implications of isotopic scrambling for the determination of kinetic isotope effects, 1254-62 Kinetic isotope effect in the reaction of 4nitrophenylnitromethane with pentamethylguanidine in toluene, 1263-7 Kinetic isotope effects in the reactions of 4nitrophenylnitromethane with alkylamidine bases in toluene, 1796-803 Kinetic isotope effect in the reaction of Pnitrophenylnitromethane with the cyclic amidine base DBU (1, 54iazabicyclo( 5,4,0)undec-5-ene), 2065-9 Chlorine kinetic isotope effects. Thermal decomposition of l-chloroethane and evaluation of possible models of activated complex, 2714-23 KAOLINITE Dielectric properties of water adsorbed by kaolinite clays, 122 1-33 Reactions of alkyl radicals with nitrogen trifluoride, 230 1-12 Mechanism of ketonization of acetic acid on anatase Ti07 surfaces, 15 17-29 KETONE KETONIZATION KINETICS Comparative study of the hydrogen reduction of nickel(I1) ions in X- and Y-zeolites, 1 5 3 8 4 Kinetics, thermochemistry and mechanism of hydrogenolysis of aliphatic aldehydes on nickel-silica, Surface properties and catalytic activity of a molybdenum-fixed catalyst.Structure of the active site and Vapour pressure measurements on some organic high explosives, 1339-45 2873-84 mechanism for selective oxidation of ethyl alcohol, 2968-8 I KNUDSEN CELL LASER PHOTOIONIZATION Laser flash photolysis study of the photoionization of chlorpromazine and promazine in solution, 181 1-19 LATEX LEAD FLUORIDE Reversible flocculation of sterically-stabilized dispersions, 33747 Thermodynamics and constitution of silicate melts.The system lead monoxide + lead difluoride + silica. 2952-67 LEAD OXIDE Application of polymer theory to silicate melts. The system metal(I1) oxide + metal(I1) fluoride + silica, Effect of lead compounds on heterogeneous oxidation catalysts, 1922-38 2942-5 1 LEAD POISONING LEED Adsorption of carbon monoxide on copper (100) studied by photoelectron spectroscopy and low energy Structure of aqueous solutions. Infrared librational band study of structure making and structure Stability of metal uncharged ligand complexes in ion exchangers. Part 3. Complex ion selectivity and Light scattering method for the study of close range structure in coagulating dispersions of equal sized Fourier inversion of light scattering intensity data from coagulating dispersions, 11 12-24 Environmental control of reactions: influence of poly(r;-glutamate) on the kinetics of decomposition of Infrared study of the adsorption of linoleic acid on alumina immersed in carbon tetrachloride, 2141-5 Sodium-23 quadrupole splittings in lyotropic liquid crystals.Relationship to electrical double layer Structural analysis of some molten materials by X-ray diffraction. Part 5. Lithium chloride, lead electron diffraction, 54654 breaking by dissolved electrolytes, 583-96 stepwise stability constants, 2470-80 spherical particles, 733-44 LINEWEAVER BURK PLOT LIBRATIONAL BAND OF WATER LIGAND METAL COMPLEX LIGHT SCAmERING hydrogen peroxide catalyzed by quaterpyridineiron (111) complex ions, 288-96 LINOLEATE LIPID LIQ theory and estimates of double layer dimensions, 1290-300 chloride and their mixtures.186 1-70 Nature of solutions of water in sulphuric acid, 21 79-92 LIQ CRYSTAL Sodium-23 quadrupole splittings in lyotropic liquid crystals. Relationship to electrical double layer Structural analysis of some molten materials by X-ray diffraction. Part 4. Alkali nitrates RN03(R = Structure of aqueous solutions. Infrared librational band study of structure making and structure theory and estimates of double layer dimensions, 1290-300 lithium, sodium, potassium, rubidium, caesium, and silver), 297-305 breaking by dissolved electrolytes, 583-96 LIQ STRUCTURE28 J.C.S. FARADAY I SUBJECT INDEX VOL. 74 (1978) Effects of water on proton migration in alcoholic solvents.Part. 5. Conductance of hydrogen chloride in Solubility of helium and hydrogen in some water + alcohol systems, 1444-56 Magneto-optical rotation studies of the structural properties of liquid mixtures. Part 1. Binary mixtures Magneto-optical rotation studies of the structural properties of liquid mixtures. Part 2. Binary mixtures Structural analysis of some molten materials by X-ray diffraction. Part 2. Lithium sulphate, sodium Inorganic photophysics in solution. Part 1. Temperature activation of decay processes in the Luminescence of Qyanoanthracene. Identification of new excimeric species, 1457-66 Luminescence excitation and de-excitation involving one-electron transfer. Aqueous solutions of 1- Luminescence and other spectroscopic studies of the reaction of pyridine and oxygen with thermally Correlation between results of X-ray photoelectron spectroscopic studies and catalytic behaviour of Thermal stability and chemical reactivity of (02-)S species adsorbed on magnesium oxide surfaces, methanol at 15,25 and 35°C and in ethanol and pentan-1-01 at 15 and 35"C, 1096-1 11 of alcohols, carboxylic acids, ethers and acetone with water, 1702-8 of some miscible organic components, 1709-1 9 LITHIUM SULPHATE X RAY DIFFRACTION sulphate and the mixed system, 795-803 luminescence of tris(2,2'-bipyridine)ruthenium(II) and trig 1 , 10-phenanthroline)rutheniwn(II) ions, 1275-89 LUMINESCENCE aminonaphthalene-4--(sodium)sulphonate, 2077-9 1 activated strontium oxide, 2763-70 magnesium oxide, 2092-1 00 MAGNESIUM 456-65 MAGNESIA Reactions of propyne and propadiene on magnesium films.Part 1. Self-hydrogenation, 2678-88 MAGNESIUM ALUMINATE Structure and catalytic activity of cobalt magnesium alumina spinel solid solutions. Part 2. Influence of sodium on the physicochemical and catalytic properties of magnesium oxide, 250-61 Thermal stability and chemical reactivity of (02-)S species adsorbed on magnesium oxide surfaces, Electron spin resonance studies of the formation and thermal stability of oxygen radicals on calcium Reflectance spectra of carbon monoxide adsorbed on alkaline earth oxides, 2278-92 Ionic oxides: distinction between mechanisms and surface roughening effects in the dissolution of Photoluminescent spectra of surface states in alkaline earth oxides, 291 3-22 Transference numbers of a 2:2 electrolyte: magnesium sulphate in water at 25" C, 1036-44 Electron paramagnetic resonance study of electron transfer at the surface of alkaline earth oxides.Mechanism of exchange in the manganese(I1)-ATP system from Fourier transform-nuclear magnetic Magnetic and optical studies of chromium oxides. Part 2. Calcination of chromic chloride supported on Magnetic and optical studies of chromium oxides. Part 3. Calcination of coprecipitated chromium and Magneto-optical rotation studies of the structural properties of liquid mixtures. Part 1. Binary mixtures Magneto-optical rotation studies of the structural properties of liquid mixtures. Part 2. Binary mixtures Magneto-optical rotation studies of electrolyte solutions. Part 5. Measurements on aqueous solutions Electromotive force studies of electrolytic dissociation.Part 12. Dissociation constants of some strongly Mechanism of exchange in the manganese(I1)-ATP system from Fourier transform-nuclear magnetic Oxidation of sulphur dioxide in aerosol droplets, catalysed by manganous sulphate, 2689-702 Thermal reactions of methyl and acet yl manganese pentacarbonyls. Part 1. Initiation of free-radical Decomposition of nitrous oxide, 1595-603 MAGNESIUM OXIDE 456-65 oxide and some other oxides, 883-92 magnesium oxide, 2907- 12 MAGNESIUM SULPHATE MAGNESUM OXIDE. MAGNETIC Reversible pyridine-induced formation of superoxide ions labelled with oxygen-1 7, 1324-8 resonance and electron paramagnetic resonance data, 21 54-8 alumina, 201 7-26 aluminium hydroxide gels, 2807-1 7 of alcohols, carboxylic acids, ethers and acetone with water, 1702-8 of some miscible organic components, 1709-19 of hydrophobic solutes, 960-3 ionizing acids at zero ionic strength and 25"C, 1 170-8 resonance and electron paramagnetic resonance data, 21 54-8 MAGNETISM MAGNETO OPTICAL ROTATION MAGNETOOPTICAL ROTATION MALEIC ACID MANGANESE MANGANESE CARBONYLJ.C.S. FARADAY I SUBJECT INDEX VOL.74 (19'18) 29 polymerization and formation of methyl(2-methyl-4-oxopentanoate), 1634-47 Thermal reactions of perfluoromethyl and perfluoroacetyl manganese pentacarbonyls. Part 2. Initiation of free-radical polymerization and formation of methyl(2-methyl-4-oxo-5,5,5-trifluoropentanoate), Structural analysis of some molten materials by X-ray diffraction. Part 3.Manganese dichloride, 804-8 Thermal behavior of gam-manganese dioxide and some reduced forms in oxygen, 23749 Mass spectrometric determination of the heats of formation of the silicon fluorides SiF(g), SiF2(g) and Thermal ion-molecule reactions in oxygen-containing molecules. Proton and hydride ion transfer Rapidly converging activity expansions for representing the thermodynamic properties of fluid systems: Ionic activities in sodium dodecyl sulphate solutions from electromotive force measurements, 1758-67 Coupled fluxes in electrochemistry. Concentration distributions near electrodialysis membranes, Shape of a meniscus in a rotating vertical tube, 555-74 Adsorption of butane-l,4-diol at the mercury-aqueous solution interface. Transition with polarization Infrared study of the adsorption of acetone on rutile, 403-17 pV-T studies on molten alkali nitrates.Part 1. Thermal pressure coefficients and compressibilities, On the hydrolysis of silver(II), thallium(II), tin(III), and copper(III), 1820-6 Electron spin resonance studies of the formation and thermal stability of oxygen radicals on calcium Application of polymer theory to silicate melts. The system metal(I1) oxide + metal(I1) fluoride + silica, Application of polymer theory to silicate melts. The system metal(I1) oxide + metal(I1) fluoride + silica, Hydrogenolysis of cyclopentane and hydrogenation of benzene on palladium catalysts of widely varying Moderated copolymerization. Part 2. Transfer constant of styryl radicals towards carbon tetrabromide: Polymerization of vinyl monomers initiated by chromium(I1) acetate + organic peroxides, 1726-37 y-Radiolysis of methane adsorbed on y-alumina.Part 2. Kinetics of reactions occurring during Ionic solvation in water + co-solvent mixtures. Part 5. Free energies of transfer of large single ions Reactions of presolvated electrons and hydrogen atoms with benzyl chloride in methanol. A pulse Infrared studies of halide ion solvation in methanol, 2 146-53 Carbonylation of methanol and ethanol on a rhodium-zeolite catalyst, 23 13-19 Influence of applied electric fields on the free radical copolymerization of methylmethacrylate and Dielectric properties of N-methyl acetamide in carbon tetrachloride solution, 11 5-22 Some properties of binary aqueous liquid mixtures. Apparent molar volumes and heat capacities at 298.Rotational barriers in N,N-dimethylbiuret. Experimental and theoretical studies, 1002-6 Mercury(63P1) photosensitization of 3-methylbut-l-ene. Part 2. Intersystem crossing and cyclization 1648-54 MANGANESE CHLORIDE MANGANESE OXIDE MASS SPECTROMETRY SiF3(g), 1089-95 MASS SPECTROSCOPY reactions in acetaldehyde, 1953-62 gases, nonelectrolyte solutions, weak and strong electrolyte solutions, 130 1-23 MCMILLEN MAYER STATE MEMBRANE 283949 MENISCUS MERCURY ELECTRODE between two ideal adsorption models, 79-92 MESITYL OXIDE METAL 153-62 METAL OXIDE oxide and some other oxides, 883-92 2942-5 1 METAL SALT 2942-5 1 METALLIC DISPERSION dispersion, 174-8 1 a penultimate unit effect in chain transfer, 1020-8 METHACRYLATE METHANE irradiation, 167686 from water into water + methanol with the neutral component removed, 636-43 radiolysis study, 964-74 METHYL METHACRY LATE METHANOL styrene.An unusual decomposition of benzoylperoxide, 1488-95 METHYLACETAMIDE 15 K over the whole mole fraction range, 1 159-69 METHYLBIURET METHYLBUTADIYL of the 2-methylbuta-l,34iyl biradical, 277-8730 J.C.S. FARADAY I SUBJECT INDEX VOL. 74 (1978) METHYLBUTADIYL BIRADICAL Mercury(63Pl) photosensitization of 3-methylbut-l-ene of the 2-methylbuta-l,3-diyl biradical, 277-87 METHYLBUTANE Part 2. Intersystem crossing and cyclization Molecular decomposition of 2,2,3,3-tetramethylbutane, 329-36 Mercury(63Pl) photosensitization of 3-methylbut-l-ene. Part 1. Reactions of vibrationally excited Mercury(63Pl) photosensitization of 3-methylbut-l-ene.Part 2. Intersystem crossing and cyclization Diffusion in binary liquid mixtures of non electrolytes, 490-7 Electron transfer from aromatic molecules to dimethylmercury via a triplet exciplex, 827-36 1 : 1 Hydrogen bonded complexes of phenol and 4-fluorophenol with 2,2,6,6-tetramethylpiperidin-l- Kinetics, thermochemistry and mechanism of hydrogenolysis of aliphatic aldehydes on nickel-silica, Kinetics of quaternization of 4-methyl and &thy1 pyridine with n-propyl and n-butyl bromide in Recoil tritium reactions with methylsiland3: pressure dependent yields, 8 18-26 Mechanism of thennolysis of tetramethylsilane and trimethylsilane, 21 71-8 Adsorption of water vapour by silica and the effect of surface methylation, 1360-72 Measurement of forces between two mica surfaces in aqueous electrolyte solutions in the range 0-100 nm Micellar catalysis of metalkcomplex formation.Kinetics of the reaction between nickel(I1) and pyridine- 2-azo-pdimethylaniline (PADA) in the presence of sodium dodecylsulphate micelles; a model system for the study of metal ion reactivity at charged interfaces, 10-21 Exchange processes in solutions of nitroxide surfactants, 220-2 Pulse radiolysis study of protoferrihaem IX intercalated in sodium dodecyl sulphate micelles, 41 8-26 Ionic activities in sodium dodecyl sulphate solutions from electromotive force measurements, 1758-67 Investigation of the size distribution of nonionic micelles formed from a polystyrene-polyisoprene block copolymer in N,N-dimethylacetamide, 2352-62 Nuclear magnetic resonance technique to distinguish between micelle size changes and secondary aggregation in anionic and nonionic surfactant solutions, 2530-4 1 Test of the nonane method for micropore evaluation.Use of nitrogen, n-hexane and carbon tetrachloride as adsorptives with ammonium phosphomolybdate, phosphotungstate and silicomolybdate as absorbents, 348-58 METHYLBUTENE triplet 3-methylbut-l+ne and the 2-methylbuta-l,34iyl biradical, 262-76 of the 2-methylbuta-l,34iyl biradical, 277-87 METHYLCYCLOTETRASILOXANE METHYLMERCURY METHYLPIPERIDINOXY L oxyl: an electron spin resonance study, 155661 METHYLPROPANAL 2873-84 METH Y LPYRIDINE sulpholane, 427-3 1 M ETHY LSILANE METHYLSILY LATION MICA 975- 100 1 MICELLE MICROPORE MO MODERATION MOLAR VOL Electrochemical decomposition of biformylperoxide.A quantum mechanical calculation, 14969 Moderation of photochemically generated hot hydrogen atoms, 1687-92 Partial molar volumes of organic compounds in water. Part 4. Aminocarboxylic acids, 858-68 Some properties of binary aqueous liquid mixtures. Apparent molar volumes and heat capacities at 298. Partial molar volumes of organic compounds in water. Part 5. Betaines of a,w-aminocarboxylic acids, Application of polymer theory to silicate melts. The system metal(I1) oxide + metal(I1) fluoride + silica, Thermodynamics and constitution of silicate melts. The system lead monoxide + lead difluoride + silica, 2952-67 MOLTEN SALTS Structural analysis of some molten materials by X-ray diffraction. Part 4. Alkali nitrates RN03(R = lithium, sodium, potassium, rubidium, caesium, and silver), 297-305 Structural analysis of some molten materials by X-ray diffraction.Part 3. Manganese dichloride, 804-8 Acid-base properties of molten oxides and metallurgical slags, 1410-1 9 Structural analysis of some molten materials by X-ray diffraction. Part 5. Lithium chloride, lead 15 K over the whole mole fraction range, 1 159-69 1268-74 MOLTEN SALT 2942-5 1 chloride and their mixtures, 1861-70J.C.S. FARADAY I SUBJECT INDEX VOL. 74 (1978) 31 MOLYBDENUM Electron paramagnetic resonance study of molybdenum supported catalysts labelled with molybdenum- Surface properties and catalytic activity of a molybdenum-fixed catalyst. Structure of the active site and Preparation of hgh surface area reduced molybdenum oxide catalysts, 2982-90 Structural characterization of high surface area reduced molybdenum oxide catalysts, 299 1-9 Infrared spectra of nitric oxide, nitrous oxide, nitrogen dioxide and oxygen adsorbed on silicon Stability of metal uncharged ligand complexes in ion exchangers.Part 2. The copper + ethylenediamine Viscoelectric coefficient for water, 450-5 Charge density effects in ion exchange, Part 2. Homovalent exchange equilibria, 1234-41 Transition metal ion exchange in zeolites. Part 3. Ternary exchange in mordenite involving ammonium, Sorption behaviour of silanated H-mordenite, 1871-8 Modified zeolites. Part 1. Dealuminated mordenites and their silanation, 278697 Modified zeolites. Part 2. Sorption by dealuminated, silanated mordenites, 2798-806 Physical adsorption of gas mixtures of 2,24imethylpropane and n-butane on Vycor glass and on Adsorption of gas mixtures of 2,24imethylpropane and n-butane on graphite and application of ideal Cyclization in the gas phase photolysis of neopentyl bromide, 77684 Kinetics of the decomposition and hydrogen reduction of nitric oxide on niobium, nickel and platinum Transition metal ion exchange in zeolites.Part 3. Ternary exchange in mordenite involving ammonium, Comparative study of the hydrogen reduction of nickel(I1) ions in X- and Y-zeolites, 1538-44 Evolution of adsorbed species during acetylene adsorption on nickel( 1 1 1) in relation to their vibrational Kinetics and mechanism of fast metal-ligand substitution processes in aqueous and micellar solutions Kinetics, thermochemistry and mechanism of hydrogenolysis of aliphatic aldehydes on nickel-silica, 95.Evidence for molybdenyl ions, 2378-84 mechanism for selective oxidation of ethyl alcohol, 2968-8 1 MOLYBDENUM.OXIDE MOLYBDENUM TRIOXIDE MONOXIDE monoxide films, 2935-41 complex in montmorillonite and sulphonic acid resin, 182-9 MONTMORILLONITE MORDENITE triethanolammonium and complexed nickel(II), 745-55 NEOPENTANE spherisorb silica, 948-59 adsorbed solution theory, 2265-70 NEOPENTYL BROMIDE NICKEL filaments at high temperatures and low pressures, 21 1-19 triethanolammonium and complexed nickel(II), 745-55 spectra, 1720-5 studied by means of a dye-laser photochemical relaxation technique, 2625-36 2873-84 NICKEL OXIDE Semiconducting oxides: effects of electronic and surface structure on dissolution kinetics of nickel oxide, Y 1615-23 dissolution kinetics, 1624-33 atoms on lithium( 1 +) doped nickel oxides, 1750-7 filaments at high temperatures and low pressures, 21 1-19 Semiconducting oxides: infrared and rate studies of the effects of surface blocking by surfactants in Correlation of the catalytic activities of oxides with their work functions.Recombination of oxygen Kinetics of the decomposition and hydrogen reduction of nitric oxide on niobium, nickel and platinum p-V-T studies on molten alkali nitrates. Part 1. Thermal pressure coefficients and compressibilities, Solubility equilibrium of silver(1) oxide in molten lithium nitrate + potassium nitrate mixtures, 1-9 Kinetics of the decomposition and hydrogen reduction of nitric oxide on niobium, nickel and platinum filaments at high temperatures and low pressures, 21 1-19 Flash photolysis study of the spectra of methyl peroxy and tert-butyl peroxy radicals and the kinetics of their mutual reactions and with nitric oxide, 1693-701 Tin oxide surfaces.Part 8. Infrared study of the mechanism of formation of a surface isocyanate species on tin oxide - 0.55 copper oxide during catalysis of the oxidation of carbon monoxide by nitric oxide, 2604- 1 6 Tin oxide surfaces. Part 9. Infrared study of the adsorption of carbon monoxide, nitric oxide and their mixtures on tin(1V) oxide gels containing ion-exchanged chromium(III), manganese(II), iron(III), cobalt(II), nickel(I1) and copper(II), 2703-1 3 Spectroscopic investigation of the structure of a novel zerovalent cobalt nitrosyl in zeolite matrixes, NIOBIUM NITRATE 153-62 NITRATE MELT NITRIC OXIDE32 J.C.S.FARADAY I SUBJECT INDEX VOL. 74 (1978) 3000-7 NITRILOTRI ACETATE NITROAROM Gamma radiolysis of copper(I1) nitrilotriacetate in aqueous solution, 622-35 In situ radiolysis electron spin resonance study of the radical-anions of substituted nitroimidazoles and In situ radiolysis electron spin resonance study of the radical-anions of substituted nitroimidazoles and Percolation of gases into (potassium, calcium)-A zeolites and their cation distribution, 61 3-2 1 Investigation of the surface heterogeneity of maximally hydroxylated nonporous silica by gas adsorption, Adsorption of water vapour by silica and the effect of surface methylation, 1360-72 Chemical energy accommodation at catalyst surfaces.Flow reactor studies of the association of nitrogen Modified zeolites. Part 2. Sorption by dealuminated, silanated mordenites, 2798-806 Infrared spectra of nitric oxide, nitrous oxide, nitrogen dioxide and oxygen adsorbed on silicon Reactions of alkyl radicals with nitrogen trifluoride, 2301-1 2 Relaxation processes of hydrogen bonded species in a polystyrene matrix, 2045-50 In situ radiolysis electron spin resonance study of the radical-anions of substituted nitroimidazoles and nitroaromatic compounds, 51 1-18 In situ radiolysis electron spin resonance study of the radical-anions of substituted nitroimidazoies and nitroaromatic compounds, 5 1 1-1 8 Kinetics of the reaction between 2,4-dinitrophenol and tri-n-octylamine in chlorobenzene solution.Diffusion and other rate-limiting factors, 1804-1 0 Kinetic analysis of deuteron-transfer reactions of alkylamidines with (2H2wnitrophenylnitromethane. Implications of isotopic scrambling for the determination of kinetic isotope effects, 1254-62 Kinetic isotope effect in the reaction of 4nitrophenylnitromethane with pentamethylguanidine in toluene, 1263-7 Kinetic isotope effects in the reactions of 4-nitrophenylnitromethane with alkylamidine bases in toluene, 1796-803 Kinetic isotope effect in the reaction of 4nitrophenylnitromethane with the cyclic amidine base DBU (1, 5diazabicyclo( 5,4,0)undec-5-ene), 2065-9 Effect of polyelectrolytes on the kinetics of ionic reactions. Part 5. Decomposition of 2,4- dinitrophenylphosphate in polycation solutions, 1 196-209 Effect of polyelectrolytes on the kinetics of ionic reactions.Part 5. Decomposition of 2,4- dinitrophenylphosphate in polycation solutions, 1 196-209 Kinetics of gas phase ion-ion recombination in nitrosyl + X- -+ nitric oxide + X for X being chlorine, bromine and iodine, 63-70 Kinetics of gas phase electron-ion recombination by nitrosyl + electron -+ nitrogen atom + oxygen atom from measurements in flames, 53-62 Spectroscopic investigation of the structure of a novel zerovalent cobalt nitrosyl in zeolite matrixes, 3000-7 nitroaromatic compounds, 51 1-1 8 nitroaromatic compounds, 51 1-1 8 NITROBENZENE NITROGEN 1045-9 atoms on metals at high temperatures, 1883-912 monoxide films, 2935-41 NITROGEN FLUORIDE NITROGEN HETEROCYCLE NITROIMIDAZOLE NITROMIDAZOLE NITROPHENOL NITROPHENYLNITROMETHANE NITROPHENY LPHOSPH ATE NITROPHENYLPHOSPHONATE NITROSYL ION NITROSYL ION RECOMBINATION NITROSYLCOBALT NITROUS Structure and catalvtic activity of cobalt magnesium alumina spinel solid solutions.Part 2. Decomposition df nitrous oxide, 1595-603 NIT ROXID E Exchange processes in solutions of nitroxide surfactants, 220-2 Electron spin resonance studies of spin-labelled polymers. Part 14. End-group mobility of polystyrene as a function of temperature and solvent, 727-32 Lithium-7, sodium-23, and beryllium-9 nuclear magnetic resonance investigations of the influence of N- substitution on the solvation interaction of amides with alkali and alkaline earth metal ions, 71-8 Diffusion in binary liquid mixtures of non electrolytes, 490-7 Water-dl-water isotope effect on nuclear magnetic relaxation of alkali halide nuclei and preferential NMR solvation in mixed solvents, 644-56J.C.S.FARADAY I SUBJECT INDEX VOL. ,+ (1978) 33 Rotational barriers in N,N-dimethylbiuret. Experimental and theoretical studies, 1002-6 Intercrystalline molecular transport in zeolites studied by uptake experiments and by nuclear magnetic Sodium-23 quadrupole splittings in lyotropic liquid crystals. Relationship to electrical double layer Nuclear magnetic relaxation studies of preferential solvation in electrolyte solutions. Indirect method Nuclear magnetic relaxation studies of preferential solvation in electrolyte solutions. Another indirect Mechanism of exchange in the manganese(I1)-ATP system from Fourier transform-nuclear magnetic Nature of solutions of water in sulphuric acid, 21 79-92 Competitive preferential solvation theory of weak molecular interactions, 221 0-28 Nuclear magnetic resonance technique to distinguish between micelle size changes and secondary Flow equation for coagulated suspensions, 785-94 Gas-liquid chromatographic studies of thermodynamic interactions in ternary systems comprising Radiotracer studies of self-diffusion in the plastic solids norbornylene and norbornane, 2562-9 Radiotracer studies of self-diffusion in the plastic solids norbornylene and norbornane, 2562-9 Surface and electrokinetic potentials of interfaces containing two types of ionizing group, 1 179-87 resonance pulsed field gradient techniques, 1210-20 theory and estimates of double layer dimensions, 1290-300 using only solvent-solvent magnetic interactions, 183448 method using only solvent magnetic interactions, 1849-60 resonance and electron paramagnetic resonance data, 21 54-8 aggregation in anionic and nonionic surfactant solutions, 2530-41 NON NEWTONIAN FLUIDS NONYL PHTHALATE dinonylphthalate + trinitrotoluene + volatile hydrocarbon, 1655-65 NORBORNANE NO RBORNY LENE NYLON NYLON FIBRE COLLOID Observation of weak primary minima in the interaction of polystyrene particles with nylon fibres, 220&9 OCTAMETHYLCYCLOTETRASILOXNE Diffusion in binary liquid mixtures of non electrolytes, 490-7 Kinetics of the reaction between 2,44initrophenol and tri-n-octylamine in chlorobenzene solution.Characterization of the hydroxyls in offretite zeolite, 1786-95 OCTYLAMINE Diffusion and other rate-limiting factors, 1804-10 OFFRETITE OLIGOMERIZATION Fourier transform infrared spectroscopy of the zeolite NaH-Y + but-l-ene system, 2027-36 OPTICAL SPECTROSCOPY Electronic absorption spectra of benzoyl radicals produced from benzoyl halides by irradiation with y- rays in organic glass, 1 188-95 Reactions of some simple a- and B-hydroxyalkyl radicals with cupric and cuprous ions in aqueous solution. Radiation chemical study, 697-7 14 Thermal stability and chemical reactivity of (02-)S species adsorbed on magnesium oxide surfaces, 456-65 Structure and catalytic activity of cobalt magnesium alumina spinel solid solutions.Part 2. Decomposition of nitrous oxide, 1595-603 Photooxidation of floating hydrocarbon oils in the presence of some naphthalene derivatives, 123-30 Interaction of oxygen with zinc surfaces, 869-82 Temperature and pressure effects on surface processes at noble metal electrodes.Part 2. Volume of adsorbed hydrogen and oxygen species at platinum and gold, 1390402 Addition of i-butane to slowly reacting mixtures of hydrogen and oxygen at 480"C, 2229-5 1 Relation between propylene oxidation performance of copper-based bimetallic catalysts and the redox behaviour of their surfaces, 2490-500 Studies of reactions of atoms in a discharge flow stirred reactor. Part 3. The oxygen atom-dihydrogen- dioxygen system, 2672-7 Oxidation of sulphur dioxide in aerosol droplets, catalysed by manganous sulphate, 2689-702 Tin oxide surfaces. Part 9. Infrared study of the adsorption of carbon monoxide, nitric oxide and their mixtures on tin(IV) oxide gels containing ion-exchanged chromium(III), manganese(II), iron(III), cobalt(II), nickel(I1) and copper(II), 2703-1 3 Surface groperties and catalytic activity of a molybdenum-fixed catalyst.Structure of the active site and mechanism for selective oxidation of ethyl alcohol, 2968-8 1 0 RG ANOCOPPER OXIDE OXIDN OXIDN KINETICS Decomposition of 2,2,3,3-tetramethylbutane in the presence of oxygen, 366-79 OXYGEN Percolation of gases into (potassium, calcium)-A zeolites and their cation distribution, 61 3-2 1 Electron paramagnetic resonance study of electron transfer at the surface of alkaline earth oxides.34 J.C.S. FARADAY I SUBJECT INDEX VOL. 74 (1978) Reversible pyridine-induced formation of superoxide ions labelled with oxygen- 17, 1324-8 activated strontium oxide, 2763-70 monoxide films, 2935-41 carbon monoxide system, 3 16-25 dioxygen system, 2672-7 OXYGEN ATOM RECOMBINATION atoms on lithium( 1 +) doped nickel oxides, 175G7 exchange of oxygen from carbon dioxide, 5068 oxide and some other oxides, 883-92 Luminescence and other spectroscopic studies of the reaction of pyridine and oxygen with thermally Modified zeolites.Part 2. Sorption by dealuminated, silanated mordenites, 2798-806 Infrared spectra of nitric oxide, nitrous oxide, nitrogen dioxide and oxygen adsorbed on silicon Studies of reactions of atoms in a discharge flow stirred reactor. Part 2. Oxygen atom + dihydrogen + Studies of reactions of atoms in a discharge flow stirred reactor.Part 3. The oxygen atomaihydrogen- Correlation of the catalytic activities of oxides with their work functions. Recombination of oxygen Study of surface atom behaviour on platinum-silica and platinum-alumina catalysts by isotropic Electron spin resonance studies of the formation and thermal stability of oxygen radicals on calcium Thermal stability and chemical reactivity of (0y)S species adsorbed on magnesium oxide surfaces, Hydrogenolysis of cyclopentane and hydrogenation of benzene on palladium catalysts of widely varying dispersion, 174-8 1 Hydrogenation of acetylene over supported metal catalysts. Part 1. Adsorption of acetylene-14C and ethylene-14C on silica supported rhodium, iridium and palladium and alumina supported palladium, Hydrogen sorption by palladium-gold wires, 223-36 Sorption of hydrogen by palladium and palladium/silver alloy wires, 326-36 X-ray photoelectron spectroscopy study of palladium and platinum ions in type Y-zeolite.Electron Hydrogenation of acetylene over supported metal catalysts. Part 2. Carbon-14 tracer study of Reactions of n-butenes on palladium films. Evidence for n-allylic species, 2652-66 Bipyridylium quaternary salts and related compounds. Part 6. Pulse radiolysis studies of the reaction of Light scattering method for the study of close range structure in coagulating dispersions of equal sized Influence of sodium on the physicochemical and catalytic properties of magnesium oxide, 250-61 Fragmentation and isomerization of protonated 3-methylbut-1-ene ions in gas-phase radiolysis, Enthalpy of interaction between some cationic polypeptides and n-alkyl sulphates in aqueous solution, Photolysis of periodate and periodic acid in aqueous solution, 2818-38 Photolysis of periodate and periodic acid in aqueous solution, 28 18-38 Electrical force between two permeable planar charged surfaces in an electrolyte solution, 26 17-24 Static relative permittivity of some electrolyte solutions in water and methanol, 2339-5 1 Temperature dependence of the low frequency dielectric dispersion in the perylene + chloranil complex, Surface tension minimum in ionic surfactant systems, 250 1-1 7 pH calibration of tetroxalate, tartrate and phthalate buffer solutions at above 100°C, 2434-51 Thallous chloride-thallous sulphide phase diagram, 2 193-9 OXYGEN ATOM OXYGEN EXCHANGE OXYGEN RADICAL OXYGEN RADICAL ANION 456-65 PALLADIUM 195-205 transfer between metal aggregates and the support as evidenced by X-ray photoelectron spectroscopy and electron spin resonance, 440-9 deactivation phenomena, 657-64 PARAQUAT paraquat radical analogues with oxygen, 665--75 spherical particles, 733-44 PARTICLE PENTENE 193944 PEPTIDE 2923-9 PERIODATE PERIODIC ACID PERMEABLE SURFACE PERMITTIVITY PERYLENE 72G6 PH PH CALIBRATION PHASE DIAGRAMJ.C.S.FARADAY I SUBJECT INDEX VOL. 74 (1978) 35 PHASE TRANSITION Heats of mixing and the solid-state transition in ( ( C ~ H ~ ) ~ P C H ~ ) I +((C~H&ASCH~), +(TCNQ)y Thermal behavior of gam-manganese dioxide and some reduced forms in oxygen, 237-49 Rate of polymorphic transformation between phases 11 and I11 of hexachloroethane, 191 3-21 Comment on rate of polymorphic transformation between phases 11 and 111 of hexachloroethane, 2750-4 Spectrophotometric investigations of aqueous solutions at elevated temperatures.Effect of temperature on the stability constants of the tris complexes of 1, IGphenanthroline, 5-nitro-1,lO-phenanthroline and 2,2’-bipyridyl with iron (11). 1081-8 Inorganic photophysics in solution. Part 1. Temperature activation of decay processes in the luminescence of tris(2,2’-bipyridine)ruthenium(II) and tris( 1,l O-phenanthroline)ruthenium(II) ions, Effect of temperature on the acid dissociation constants of 1 ,I@-phenanthroline and some related bases Infrared study of the adsorption of phenols on silica immersed in heptane, 1137-45 1 : 1 Hydrogen bonded complexes of phenol and 4-fluorophenol with 2,2,6,6-tetramethylpiperidin-l- Examination of activation parameters for the dissociation of iron(II1) complexes as a means of assessing Resonance Raman spectra of carbonium ions adsorbed on porous Vycor glass, 1562-8 Effect of molecular environment and of excitation energy on electron photoejection from monophenylphosphate, 1029-35 Test of the nonane method for micropore evaluation.Use of nitrogen, n-hexane and carbon tetrachloride as adsorptives with ammonium phosphomolybdate, phosphotungstate and silicomolybdate as absorbents, 348-58 Electromotive force studies of electrolytic dissociation. Part 12. Dissociation constants of some strongly ionizing acids at zero ionic strength and 25°C 1 17&8 Test of the nonane method for micropore evaluation.Use of nitrogen, n-hexane and carbon tetrachloride as adsorptives with ammonium phosphomolybdate, phosphotungstate and silicomolybdate as absorbents, 348-58 (0 5 x 5 l), anion radical salts, 1 9 M PHENANTHROLINE 1275-89 PH EN ANTH ROLIUM in water, 1075-80 PHENOL oxyl: an electron spin resonance study, 1556-61 mechanistic ambiguities. Data for phenolic complexes, 525-9 PHENOLIC COMPLEXES PHENYLETHYLENE PHENY LPHOSPH ATE PHOSPHOMOLYBDATE PHOSPHORIC ACID PHOSPHOTUNGSTATE PHOTOCHEM PHOTOCHEM RELAXATION Self-reactions of isopropylperoxy radicals in the gas phase, 2293-300 Kinetics and mechanism of fast metal-ligand substitution processes in aqueous and micellar solutions Effect of oxygen chemisorption and photodesorption on the conductivity of zinc oxide powder layers, Correlation between results of X-ray photoelectron spectroscopic studies and catalytic behaviour of magnesium oxide, 2092- 100 X-ray photoelectron spectroscopic (X-p.e.s.) studies on in situ photoinduced decomposition of inorganic molecular ions. Part 2.Na(C10,) system: mechanistic (x = 3,4) and variable-temperature (x = 3) investigations, 2252-70 monophenylphosphate, 1029-35 dimethylene), 603-12 studied by means of a dye-laser photochemical relaxation technique, 2625-36 PHOTOCOND 3 1-45 PHOTOELECTRON SPECTRA PHOTOIONIZATION Effect of molecular environment and of excitation energy on electron photoejection from Solid state reversible reactions. Thermal behaviour of the photoisomer of bi(anthracene9,lO- Photoluminescent spectra of surface states in alkaline earth oxides, 291 3-22 Surface properties and catalytic activity of a molybdenum-fixed catalyst.Structure of the active site and Cyclization in the gas phase photolysis of neopentyl bromide, 776-84 Energy distribution and mechanism in 3-chloro-3-methyldiazirine photolysis, 809-1 7 Electron transfer from aromatic molecules to dimethylmercury via a triplet exciRlex, 827-36 Cadmium photosensitized decomposition of propane at 265°C and at A = 3261 A, 1545-55 PHOTOISOMER PHOTOLUMINESCENCE mechanism for selective oxidation of ethyl alcohol, 2968-8 1 PHOTOLYSIS36 J.C.S. FARADAY I SUBJECT INDEX VOL. 74 (1978) Moderation of photochemically generated hot hydrogen atoms, 1687-92 Flash photolysis study of the spectra of methyl peroxy and tert-butyl peroxy radicals and the kinetics of Laser flash photolysis study of the photoionization of chlorpromazine and promazine in solution, Reactions of alkyl radicals with nitrogen trifluoride, 2301-1 2 Photolysis of periodate and periodic acid in aqueous solution, 28 18-38 Carbon difluoride emission during vacuum ultraviolet photodissociation of dibromodifluoromethane, Photooxidation of floating hydrocarbon oils in the presence of some naphthalene derivatives, 123-30 Self-reactions of isopropylperoxy radicals in the gas phase, 2293-300 Mercury(63Pl) photosensitization of 3-methylbut-l-ene.Part 1. Reactions of vibrationally excited Mercury(63Pl) photosensitization of 3-methylbut-l-ene. Part 2. Intersystem crossing and cyclization Activity coefficients for the system hydrogen chloride + barium chloride + water at 298.15 K. Kinetics of the decomposition and hydrogen reduction of nitric oxide on niobium, nickel and platinum X-ray photoelectron spectroscopy study of palladium and platinum ions in type Y-zeolite.Electron Study of surface atom behaviour on platinum-silica and platinum-alumina catalysts by isotropic Characterization of supported platinum, hydrogenation and hydrogen-deuterium equilibration, 1064-74 Temperature and pressure effects on surface processes at noble metal electrodes. Part 1. Entropy of Temperature and pressure effects on surface processes at noble metal electrodes. Part 2. Volume of Adsorption of hydrogen on a platinum-graphite catalyst. Part 1. Electron spin resonance measurement Hydrogenolysis of cyclopentane and hydrogenation of benzene on palladium catalysts of widely varying Model of polarisable spheres: a reappraisal, 756-7 Rayleigh scattering depolarization ratio and the molecular polarizability anisotropy for gases, 3008-1 5 Theory of electrolytes.Part 4. Model of polarizable dielectric spheres. Structure around ions in solution Polarization in electrodialysis. Rotating-disc studies, 2850-7 Comment on rate of polymorphic transformation between phases I1 and I11 of hexachloroethane, 2750-4 Surface and electrokinetic potentials of interfaces containing two types of ionizing group, 1179-87 Hydration, dehydrative counter-ion binding and helix formation of charged poly(a-amino acid)s in Enthalpy of interaction between some cationic polypeptides and n-alkyl sulphates in aqueous solution, Effect of polyelectrolytes on the kinetics of ionic reactions.Part 5. Decomposition of 2,4- Effect of polyelectrolytes on the kinetics of ionic reactions. Part 5. Decomposition of 2,4- Effect of polyelectrolytes upon the kinetics of ionic reactions. Part 6. Some general aspects, 2460-9 Absorption spectra of radical ions of polyenones of biological interest, 538-45 Reversible flocculation of sterically-stabilized dispersions, 337-47 their mutual reactions and with nitric oxide, 1693-701 181 1-19 2930-4 PHOTOOXIDN PHOTOSENSITIZATION triplet 3-methylbut-l-ene and the 2-methylbuta-l,34iyl biradical, 262-76 of the 2-methylbuta-l,3-diyl biradical, 277-87 Comparison of Scatchard’s and Pitzer’s interpretations, 83745 filaments at high temperatures and low pressures, 21 1-19 transfer between metal aggregates and the support as evidenced by X-ray photoelectron spectroscopy and electron spin resonance, 440-9 exchange of oxygen from carbon dioxide, 506-8 chemisorption of hydrogen at platinum surfaces, 1373-89 adsorbed hydrogen and oxygen species at platinum and gold, 1390-402 in the gas-solid system, 1963-72 dispersion, 174-8 1 PITZER EQUATION PLATINUM POISON POLARIS ATION POLARIZABILITY POLARIZABLE DIELEC SPHERE in relation to ionic solvation and activity coefficients, 2385-92 POLARIZATION POLEMIC POLYAMIDE POLYAMINO ACID aqueous alcohol as revealed by a preferential binding study, 2583-96 POLYARGININE HYDROCHLORIDE 2923-9 POLYCATION dinitrophenylphosphate in polycation solutions, 1 196-209 dinitrophenylphosphate in polycation solutions, 1 196-209 POLYELECTROLYTE POLY ENONE POLYETHYLENE OXIDEJ.C.S.FARADAY I SUBJECT INDEX VOL. 74 (1978) 37 POLYETHYLENEIMINE Effect of polyelectrolytes on the kinetics of ionic reactions. Part 5. Decomposition of 2,4- Environmental control of reactions: influence of poly(L-glutamate) on the kinetics of decomposition of Enthalpy of interaction between some cationic polypeptides and n-alkyl sulphates in aqueous solution, Hydration, dehydrative counter-ion binding and helix formation of charged poly(a-amino acid)s in Enthalpy of interaction between some cationic polypeptides and n-alkyl sulphates in aqueous solution, Electron spin resonance studies of spin-labelled polymers. Part 14. End-group mobility of polystyrene Light scattering method for the study of close range structure in coagulating dispersions of equal sized Application of polymer theory to silicate melts.The system metal(I1) oxide + metal(I1) fluoride + silica, Moderated copolymerization. Part 2. Transfer constant of styryl radicals towards carbon tetrabromide: a penultimate unit effect in chain transfer, 1020-8 Thermal reactions of methyl and acetyl manganese pentacarbonyls. Part 1. Initiation of free-radical polymerization and formation of methyl(2-methyl-4-oxopentanoate), 1634-47 Thermal reactions of perfluoromethyl and peduoroacetyl manganese pentacarbonyls. Part 2. Initiation of free-radical polymerization and formation of methyl(2-methyl-4axo5,5,~trifluoropentanoate), Polymerization of vinyl monomers initiated by chromium(I1) acetate + organic peroxides, 1726-37 Living radical polymerizations of vinyl monomers initiated by aged chromium(I1) + BPO in Theory of compartmentalized free-radical polymerization reactions.Part 2,205 1-64 Adsorption and polymerization of acetylene on oxide surfaces. A Raman study, 2542-9 Comment on rate of polymorphic transformation between phases I1 and I11 of hexachloroethane, 27504 Reversible flocculation of sterically-stabilized dispersions, 337-47 Electron spin resonance studies of spin-labelled polymers. Part 14. End-group mobility of polystyrene Light scattering method for the study of close range structure in coagulating dispersions of equal sized Fourier inversion of light scattering intensity data from coagulating dispersions, 11 12-24 Origin of charge on colloidal particles in butanol, 1583-9 Calculation of dispersion force interactions between colloidal particles in butan-l-ol,2008-16 Observation of weak primary minima in the interaction of polystyrene particles with nylon fibres, 2200-9 Colloid stability in butanol, 2271-7 Relaxation processes of hydrogen bonded species in a polystyrene matrix, 2045-50 Studies in the system calcium sulphate monohydrate.Part 6. Surface chemistry and porosity of the Solid state reactions of radio sulphur in silver-doped potassium chloride, 2452-9 Electrical conductivities of shock-compressed solutions of potassium iodide in organic solvents, 2742-9 Radiolysis of the alkali nitrates, 919-32 Aqueous solutions containing amino acids and peptides.Part 5. Gibbs free energy of interaction of Rotational barriers in N,N-dimethylbiuret. Experimental and theoretical studies, 1002-6 Flame photometric determinations of diffusion coefficients. Part 6. Results for carbon monoxide and dinitrophenylphosphate in polycation solutions, 1 196-209 hydrogen peroxide catalyzed by quaterpyridineiron (111) complex ions, 288-96 POLYGLUTAMATE POLYHISTIDINE HYDROCHLORDE 2923-9 POLY LYSINE aqueous alcohol as revealed by a preferential binding study, 2583-96 2923-9 POLYMER as a function of temperature and solvent, 727-32 spherical particles, 733-44 POLYLYSINE HYDROBROMIDE POLYMER THEORY 2942-5 1 POLYMN 1648-54 homogeneous solution, 1738-49 POLYMORPHIC TRANSFORMATION POLYSTYRENE as a function of temperature and solvent, 727-32 spherical particles, 733-44 POLYSTYRENE MATRIX POROSITY calcium sulphate hemihydrates, 1477-87 POTASSIUM CHLORIDE POTASSIUM IODIDE POTASSIUM NITRATE POTENTIAL glycine with some alkali metal chlorides at 298.15 K, 2771-8 POTENTIAL BARRIER POTENTIAL FUNCTION free atoms of bromine, iodine, and thallium, 715-1938 J.C.S.FARADAY I SUBJECT INDEX VOL. 74 (1978) PREFERENTIAL SOLVATION THEORY PRESSURE MEASUREMENT Competitive preferential solvation theory of weak molecular interactions, 221 0-28 Analysis of pressure changes for simultaneous first-order decomposition reactions in a gas-kinetic Laser flash photolysis study of the photoionization of chlorpromazine and promazine in solution, Reactions of propyne and propadiene on magnesium films. Part 1.Self-hydrogenation, 2678-88 Free energies and entropies of transfer of hydrogen halides from water to aqueous alcohols and the system with dead-space, 2755-9 PROMAZINE 181 1-19 PROPADIENE PROPAN 2 OL structure of aquo-organic solvents, 1051-63 PROPANE Cadmium photosensitized decomposition of propane at 265°C and at A = 3261 i, 1545-55 PROPENE Role of Broensted acid centres for alkene double bond migration over alumina at temperatures above Kinetics of quaternization of 4-methyl and 4-ethyl pyridine with n-propyl and n-butyl bromide in Relation between propylene oxidation performance of copper-based bimetallic catalysts and the redox 450 K, 498-505 PROPYL BROMIDE sulpholane, 427-3 1 behaviour of their surfaces, 2490-500 PROPY LENE PROPYNE Allene isomerization, 1337-8 Reactions of propyne and propadiene on magnesium films.Part 1. Pulse radiolysis study of protoferrihaem IX intercalated in sodium Nature of solutions of water in sulphuric acid, 21 79-92 PROTOFERRIHAEM PROTOLYSIS PROTON TRANSFER Self-hydrogenation, 2678-88 dodecyl sulphate micelles, 418-26 Kinetic isotope effect in the reaction of 4nitrophenylnitromethane with pentamethylguanidine in Kinetic isotope effects in the reactions of 4-nitrophenylnitromethane with alkylamidine bases in toluene, Kinetic analysis of deuteron-transfer reactions of alkylamidines with (2H2)4nitrophenylnitromethane. Implications of isotopic scrambling for the determination of kinetic isotope effects, 1254-62 Kinetic isotope effect in the reaction of 4-nitrophenylnitromethane with pentamethylguanidine in toluene, 1263-7 Kinetic isotope effect in the reaction of 4-nitrophenylnitromethane with the cyclic amidine base DBU (1, 5-diazabicyclo(5,4,0)undec-5-ene), 2065-9 Protonic conductivity in layered tin chloride dihydrate single crystal, 2333-5 1 Origin of charge on colloidal particles in butanol, 1583-9 Calculation of dispersion force interactions between colloidal particles in butan-1-01, 2008- 16 Heterocoagulation.Part 3. Interactions of polyvinyl chloride latex with Ludox HS silica, 1346-59 Electron paramagnetic resonance study of electron transfer at the surface of alkaline earth oxides. Reversible pyridine-induced formation of superoxide ions labelled with oxygen-1 7, 1324-8 Luminescence and other spectroscopic studies of the reaction of pyridine and oxygen with thermally activated strontium oxide, 2763-70 Micellar catalysis of metal-complex formation. Kinetics of the reaction between nickel(I1) and pyridine- 2-azo-pdimethylaniline (PADA) in the presence of sodium dodecylsulphate micelles; a model system for the study of metal ion reactivity at charged interfaces, 10-21 Very low pressure pyrolysis (VLPP) of 3-chloropropionitrile, 912-1 8 Gas phase pyrolysis of cyclopropene.Part 1. Kinetics and mechanism, 1 146-58 Molecular decomposition of 2,2,3,3-tetramethylbutane, 1 329-36 Shock tube studies of the high temperature pyrolysis of acetylene and ethylene, 1403-9 Evidence for a molecular component in the thermal decomposition of azomethane, 2121-9 Chlorine kinetic isotope effects. Thermal decomposition of l-chloroethane and evaluation of possible Water-d2-water isotope effect on nuclear magnetic relaxation of alkali halide nuclei and preferential toluene, 1263-7 1796-803 PROTONATION PROTONIC CONDUCTANCE PTFE PVC PYRIDINE PYRIDINEAZODIMETHYLANILINE PYROLYSIS models of activated complex, 27 14-23 QUADRUPOLE INTERACTIONJ.C.S.FARADAY I SUBJECT INDEX VOL. 74 (1978) 39 solvation in mixed solvents, 644-56 QUATERNARY AMMONIUM SURFACTANT QUATERNIZATION sulpholane, 427-31 QUATERPYRIDINE IRON COMPLEX IONS hydrogen peroxide catalyzed by quaterpyridineiron (111) complex ions, 288-96 Exchange processes in solutions of nitroxide surfactants, 220-2 Kinetics of quaternization of &methyl and k t h y l pyridine with n-propyl and n-butyl bromide in Environmental control of reactions: influence of poly(L-glutamate) on the kinetics of decomposition of Electron transfer from aromatic molecules to dimethylmercury via a triplet exciplex, 827-36 Effect of molecular environment and of excitation energy on electron photoejection from Photoluminescent spectra of surface states in alkaline earth oxides, 29 13-22 Carbon difluoride emission during vacuum ultraviolet photodissociation of dibromodifluoromethane, Luminescence excitation and de-excitation involving one-electron transfer. Aqueous solutions of 1- In situ radiolysis electron spin resonance study of the radical-anions of substituted nitroimidazoles and Absorption spectra of radical ions of polyenones of biologcal interest, 538-45 Heats of mixing and the solid-state transition in ((C6H5)3PCH3)l~xf((C6H5)3ASCH3)x +(TCNQ)y Solid state reactions of radio sulphur in silver-doped potassium chloride, 2452-9 Pulse radiolysis study of protoferrihaem IX intercalated in sodium dodecyl sulphate micelles, 41 8-26 Radicals derived from 1,4-disubstituted anthraquinones. Further evidence for association of quinones in Gamma radiolysis of copper(I1) nitrilotriacetate in aqueous solution, 622-35 Bipyridylium quaternary salts and related compounds.Part 6. Pulse radiolysis studies of the reaction of Reactions of some simple a- and p-hydroxyalkyl radicals with cupric and cuprous ions in aqueous Radiolysis of the alkali nitrates, 919-32 Reactions of presolvated electrons and hydrogen atoms with benzyl chloride in methanol. A pulse Electronic absorption spectra of benzoyl radicals produced from benzoyl halides by irradiation with y- y-Radiolysis of methane adsorbed on y-alumina.Part 2. Kinetics of reactions occurring during On the hydrolysis of silver(II), thallium(II), tin(III), and copper(III), 1820-6 Fragmentation and isomerization of protonated 3-methylbut-l-ene ions in gas-phase radiolysis, X-ray photoelectron spectroscopic (X-p.e.s.) studies on in situ photoinduced decomposition of inorganic Photolysis of periodate and periodic acid in aqueous solution, 2818-38 Radiotracer studies of self-diffusion in the plastic solids norbornylene and norbornane, 2562-9 Spectrochemistry of solutions. Part 5. Raman spectroscopic study of the coordination of silver(1) ions in Resonance Raman spectra of carbonium ions adsorbed on porous Vycor glass, 1562-8 Adsorption and polymerization of acetylene on oxide surfaces.A Raman study, 2542-9 Rayleigh scattering depolarization ratio and the molecular polarizability anisotropy for gases( Reactions of n-butenes on palladium films. Evidence for n-allylic species, 2652-66 Surface properties and catalytic activity of a molybdenum-fixed catalyst. Structure of the active site and Recoil tritium reactions with methylsilaned3: pressure dependent yields, 8 18-26 QUENCHING monophenylphosphate, 1029-35 293W RADIATION aminonaphthalene+sodium)sulphonate, 2077-9 1 nitroaromatic compounds, 51 1-1 8 RADICAL ANION RADICAL ION RADICAL SALT (0 5 x RADIOCHEM RADIOLYSIS l), anion radical salts, 1 9 W solution, 597-602 paraquat radical analogues with oxygen, 665-75 solution.Radiation chemical study, 697-714 radiolysis study, 964-74 rays in organic glass, 1 188-95 irradiation, 1676-86 1939-44 molecular ions. Part 2. Na(C10,) system: mechanistic (x = 3,4) and variable-temperature (x = 3) investigations, 2252-70 RADIOTRACER RAMAN liquid ammonia by thiocyanate ions, 432-9 RAYLEIGH SCATTERING 3008-1 5 REACTION mechanism for selective oxidation of ethyl alcohol, 2968-8 1 RECOIL REACTION40 J.C.S. FARADAY I SUBJECT INDEX VOL. 74 (1978) RECOMBINATION Mutual reaction of isopropyl radicals, 301 6-21 REDLICH KISTER Analysis of activity data in three component systems by means of an augmented Redlich-Kister Comparative study of the hydrogen reduction of nickel(I1) ions in X- and Y-zeolites, 1538-44 Studies of reactions of atoms in a discharge flow stirred reactor.Part 3. The oxygen atomdihydrogen- dioxygen system, 2672-7 Tin oxide surfaces. Part 9. Infrared study of the adsorption of carbon monoxide, nitric oxide and their mixtures on tin(1V) oxide gels containing ion-exchanged chromium(III), manganese(II), iron(III), cobalt(II), nickel(I1) and copper(II), 2703-1 3 Infrared spectra of nitric oxide, nitrous oxide, nitrogen dioxide and oxygen adsorbed on silicon monoxide films, 293 5-4 1 Kinetics of the decomposition and hydrogen reduction of nitric oxide on niobium, nickel and platinum filaments at high temperatures and low pressures, 21 1-19 Electrocheiical decomposition of biformylperoxide. A quantum mechanical calculation, 1496-9 Relation between propylene oxidation performance of copper-based bimetallic catalysts and the redox Luminescence and other spectroscopic studies of the reaction of pyridine and oxygen with thermally Reexamination of the diffuse reflectance spectra of copper/alumina catalysts, 758-61 Surface properties and catalytic activity of a molybdenum-fixed catalyst.Structure of the active site and Hydration, dehydrative counter-ion binding and helix formation of charged poly(a-amino acid)s in Mechanism of exchange in the manganese(I1)-ATP system from Fourier transform-nuclear magnetic Thermodynamic study of disorder in mercury(I1) diamminodichloride and mercury(I1) Hydrogenation of acetylene over supported metal catalysts. Part 1. Adsorption of acetylene-14C and Hydrogenation of acetylene over supported metal catalysts. Part 2.Carbon-14 tracer study of Carbonylation of methanol and ethanol on a rhodium-zeolite catalyst, 23 13-19 Relation between propylene oxidation performance of copper-based bimetallic catalysts and the redox Infrared study of carbon monoxide chemisorption on zeolite and alumina supported rhodium, 2570-80 Mercury(8Pl) photosensitization of 3-methylbut-l-ene. Part 2. Intersystem crossing and cyclization of the 2-methylbuta-l,3-diyl biradical, 277-87 Kinetics and mechanism of fast metal-ligand substitution processes in aqueous and micellar solutions studied by means of a dye-laser photochemical relaxation technique, 2625-36 Ring-disc electrodes. Part 18. Collection efficiency for high frequency a.c, 1007-19 Polarization in electrodialysis. Rotating-disc studies, 2850-7 Electron spin resonance studies of spin-labelled polymers.Part 14. End-group mobility of polystyrene Inorganic photophysics in solution. Part 1. Temperature activation of decay processes in the formalism, 393-402 REDN REDN CATALYSIS REDOX behaviour of their surfaces, 2490-500 activated strontium oxide, 2763-70 REFLECTANCE REFLECTANCE SPECTRA REFLECTION mechanism for selective oxidation of ethyl alcohol, 2968-8 1 aqueous alcohol as revealed by a preferential binding study, 2583-96 resonance and electron paramagnetic resonance data, 21 54-8 diamminodibromide, 2363-77 ethylen44C on silica supported rhodium, indium and palladium and alumina supported palladium, deactivation phenomena, 657-64 behaviour of their surfaces, 2490-500 REFRACTIVE INDEX RELAXATION RESIDUAL ENTROPY RHODIUM 195-205 RING CLOSURE RING DISC ELECTRODE ROTATING DISC ROTATION BARRIER as a function of temperature and solvent, 727-32 luminescence of tris(2,2’-bipyridine)ruthenium(II) and tns( 1, 10-phenanthroline)ruthenium(II) ions, 1275-89 RUTHENIUM RUTILE SALT Infrared study of the adsorption of acetone on rutile, 403-17 Low temperature infrared spectroscopic study of the solvation of ions in water, 251 8-29J.C.S.FARADAY I SUBJECT INDEX VOL. 74 (1978) 41 SCATCHARD EQUATION SELF COMPLEXED ELECTROLYTE Activity coefficients for the system hydrogen chloride + barium chloride + water at 298.15 K. Transport in aqueous solutions of Group IIB metal salts (298.15 K). Part 4. Interpretation and Self-diffusion coefficients of water in pure water and in aqueous solutions of several electrolytes with Semiconducting oxides: effects of electronic and surface structure on dissolution kinetics of nickel oxide, Semiconducting oxides: infrared and rate studies of the effects of surface blocking by surfactants in Effect of viscosity on the bimolecular termination rate constants for semiquinone radicals in solution: a Shock tube studies of the high temperature pyrolysis of acetylene and ethylene, 1403-9 Electrical conductivities of shock-compressed solutions of potassium iodide in organic solvents, 2742-9 Modified zeolites.Part 2. Sorption by dealuminated, silanated mordenites, 2798-806 Sorption behaviour of silanated H-mordenite, 1871-8 Modified zeolites. Part 1. Dealuminated mordenites and their silanation, 2786-97 Recoil tritium reactions with methylsilane43: pressure dependent yields, 8 18-26 Investigation of the surface heterogeneity of maximally hydroxylated nonporous silica by gas adsorption, Infrared study of the adsorption of anisoles on silica immersed in heptane, 1125-36 Infrared study of the adsorption of phenols on silica immersed in heptane, 1 137-45 Heterocoagulation.Part 3. Interactions of polyvinyl chloride latex with Ludox HS silica, 1346-59 Adsorption of water vapour by silica and the effect of surface methylation, 1360-72 Infrared study of the adsorption of diketones on silica immersed in carbon tetrachloride, 2130-40 Electron paramagnetic resonance study of molybdenum supported catalysts labelled with molybdenum- Infrared study of adsorption on silica from two-component and three-component liquid mixtures, Application of polymer theory to silicate melts.The system metal(I1) oxide + metal(I1) fluoride + silica, Thermodvnamics and constitution of silicate melts. The svstem lead monoxide + lead difluoride + Comparison of Scatchards and Pitzer’s interpretations, 83745 prediction of isotopic diffusion coefficients for cadmium in dilute solutions of cadmium iodide, 103-14 oxygen-18 and deuterium as tracers, 1879-8 1 1615-23 dissolution kinetics, 1624-33 kinetic ESR study, 21 1 1-20 SELF DIFFUSION SEMICONDUCTOR OXIDE SEMIQUINONE SHOCK TUBE SHOCK WAVE SILANATED MORDENITE SILANATION SILANE SILICA 1045-9 95. Evidence for molybdenyl ions, 2378-84 2393-407 2942-5 1 silica, 5952-67 mechanism for selective oxidation of ethyl alcohol, 2968-81 Surface properties and catalytic activity of a molybdenum-fixed catalyst.Structure of the active site and SILICON Infrared spectra of nitric oxide, nitrous oxide, nitrogen dioxide and oxygen adsorbed on silicon monoxide films, 2935-41 Mass spectrometric determination of the heats of formation of the silicon fluorides SiF(g), SiFZ(g) and SiF3(g), 1089-95 SILICON MONOXIDE Infrared spectra of nitric oxide, nitrous oxide, nitrogen dioxide and oxygen adsorbed on silicon monoxide films, 2935-41 Test of the nonane method for micropore evaluation. Use of nitrogen, n-hexane and carbon tetrachloride as adsorptives with ammonium phosphomolybdate, phosphotungstate and silicomolybdate as absorbents, 348-58 SILICON FLUORIDE SILICOTUNGSTATE SILVER Sorption of hydrogen by palladium and palladium/silver alloy wires, 326-36 On the hydrolysis of silver(II), thallium(II), tin(III), and copper(III), 182M Relation between propylene oxidation performance of copper-based bimetallic catalysts and the redox Spectrochemistry of solutions.Part 5. Raman spectroscopic study of the coordination of silver(1) ions in Thallous chloride-thallous sulphide phase diagram, 2 193-9 behaviour of their surfaces, 2490-500 liquid ammonia by thiocyanate ions, 432-9 SILVER AMMINE SILVER CHLORIDE SULPHIDE SYSTEM42 J.C.S. FARADAY I SUBJECT INDEX VOL. 74 (1978) SILVER OXIDE SILY LATION SITE GROUP INTERACTTON Solubility equilibrium of silver(1) oxide in molten lithium nitrate + potassium nitrate mixtures, 1-9 Adsorption of water vapour by silica and the effect of surface methylation, 136&72 Site group interaction effects in zeolite-Y.Part 2. Sodium-silver selectivity in different site groups, Acid-base properties of molten oxides and metallurgcal slags, 1410-19 Enthalpy of interaction between some cationic polypeptides and n-alkyl sulphates in aqueous solution, X-ray photoelectron spectroscopic (X-p.e.s.) studies on in situ photoinduced decomposition of inorganic 13645 SLAG SODIUM ALKYL SULPHATE 2923-9 SODIUM CHLORATE molecular ions. Part 2. Na(C10,) system: mechanistic (x = 3,4) and variable-temperature (x = 3) investigations, 2252-70 some a,nFamino acids with sodium chloride at 298.15 K, 2779-85 SODIUM CHLORIDE Aqueous solutions containing amino acids and peptides. Part 8. Gibbs free energy of interaction of Polarization in electrodialysis.Rotating4isc studies, 2850-7 Micellar catalysis of metal-complex formation. Kinetics of the reaction between nickel(I1) and pyridine- 2-azo-pdimethylaniline (PADA) in the presence of sodium dodecylsulphate micelles; a model system for the study of metal ion reactivity at charged interfaces, 10-21 Pulse radiolysis study of protoferrihaem IX intercalated in sodium dodecyl sulphate micelles, 41 8-26 Nuclear magnetic resonance technique to distinguish between micelle size changes and secondary aggregation in anionic and nonionic surfactant solutions, 2530-41 Modified zeolites. Part 1. Dealuminated mordenites and their silanation, 2786-97 Radiolysis of the alkali nitrates, 919-32 Hydration, dehydrative counter-ion binding and helix formation of charged poly(a-amino acid)s in Structural analysis of some molten materials by X-ray diffraction.Part 2. Lithium sulphate, sodium Fourier inversion of light scattering intensity data from coagulating dispersions, 1 1 12-24 Surface and electrokinetic potentials of interfaces containing two types of ionizing group, 1 179-87 Test of the nonane method for micropore evaluation. Use of nitrogen, n-hexane and carbon tetrachloride as adsorptives with ammonium phosphomolybdate, phosphotungstate and silicomolybdate as absorbents, 348-58 (0 5 x 5 l), anion radical salts, 1 9 W SODIUM DODECYL SULPHATE SODIUM MORDENITE SODIUM NITRATE SODIUM POLYGLUTAMATE aqueous alcohol as revealed by a preferential binding study, 2583-96 sulphate and the mixed system, 795-803 SODIUM SULPHATE MOLTEN SALTS SOL SOLID SOLID SOLN Heats of mixing and the solid-state transition in ( ( C ~ H ~ ) ~ P C H ~ ) I ,+((C~H~)~ASCH~),+ (TCNQ)y Thermal behavior of gam-manganese dioxide and some reduced forms in oxygen, 237-49 Theory of electrolytes.Part 4. Model of polarizable dielectric spheres. Structure around ions in solution in relation to ionic solvation and activity coefficients, 2385-92 Structure of aqueous solutions. Infrared librational band study of structure making and structure breaking by dissolved electrolytes, 583-96 SOLVATED ELECTRONS Reactions of presolvated electrons and hydrogen atoms with benzyl chloride in methanol. A pulse radiolysis study, 964-74 Lithium-7, sodium-23, and beryllium-9 nuclear magnetic resonance investigations of the influence of N- substitution on the solvation interaction of amides with alkali and alkaline earth metal ions, 71-8 Washburn numbers.Part 3. Alkali-metal chlorides in the DMSO + water system; comparison with hydrochloric acid; structural effects, 380-92 Water-dz-water isotope effect on nuclear magnetic relaxation of alkali halide nuclei and preferential solvation in mixed solvents, 644-56 Calculations on ionic solvation. Part 1. Free energies of solvation of gaseous univalent ions using a one- layer continuum model, 1604-14 Nuclear magnetic relaxation studies of preferential solvation in electrolyte solutions. Indirect method SOLID SOLUTION SOLN SOLN STRUCTURE SOLVATIONJ.C.S. FARADAY I SUBJECT INDEX VOL. 74 (1978) 43 using only solvent-solvent magnetic interactions, 183448 Nuclear magnetic relaxation studies of preferential solvation in electrolyte solutions.Another indirect method using only solvent magnetic interactions, 1849-60 Infrared studies of halide ion solvation in methanol, 2146-53 Theory of electrolytes. Part 4. Model of polarizable dielectric spheres. Structure around ions in solution in relation to ionic solvation and activity coefficients, 2385-92 Hydration, dehydrative counter-ion binding and helix formation of charged poly(a-amino acid)s in aqueous alcohol as revealed by a preferential binding study, 2583-96 Calculations on ionic solvation. Part 2. Entropies of solvation of gaseous univalent ions using a one- layer continuum model, 2858-67 Magneto-optical rotation studies of electrolyte solutions.Part 5. Measurements on aqueous solutions of hydrophobic solutes, 960-3 Free energes and entropies of transfer of hydrogen halides from water to aqueous alcohols and the structure of aquo-organic solvents, 1051-63 Some properties of binary aqueous liquid mixtures. Apparent molar volumes and heat capacities at 298. 15 K over the whole mole fraction range, 1 159-69 Solubility of helium and hydrogen in some water + alcohol systems, 1444-56 Percolation of gases into (potassium, calcium)-A zeolites and their cation distribuiion, 61 3-21 Modified zeolites. Part 2. Sorption by dealuminated, silanated mordenites, 2798-806 pV-T studies on molten alkali nitrates. Part 2. Internal energes and equation of state, 163-73 Spectroscopic investigation of the structure of a novel zerovalent cobalt nitrosyl in zeolite matrixes, Physical adsorption of gas mixtures of 2,24imethylpropane and n-butane on Vycor glass and on Kinetics of flowing dispersions.Part 1 1. Dielectric constants of streaming suspensions of spheroids, Structure and catalytic activity of cobalt magnesium alumina spinel solid solutions. Part 2. Stability of metal uncharged ligand complexes in ion exchangers. Part 3. Complex ion selectivity and Stability constants for cadmium iodide complexes in aqueous cadmium iodide (298.15 K), 484-9 Spectrophotometric investigations of aqueous solutions at elevated temperatures. Effect of temperature on the stability constants of the tris complexes of 1,10-phenanthroline, 5-nitro-l,l0-phenanthroline and 2,2'-bipyridyl with iron (11), 1081-8 SOLVATION ENTROPY SOLVENT STRUCTURE SOLY SORPTION SPECIFIC HEAT SPECTRA 3000-7 SPHERISORB spherisorb silica, 948-59 SPHEROID 1242-53 SPINEL Decomposition of nitrous oxide, 1595-603 stepwise stability constants, 2470-80 STABILITY STABILITY CONSTANTS STAINLESS STEEL STANNIA Adsorption/absorption characteristics of caesium on oxidized stainless steel, 1420-34 Tin oxide surfaces.Part 4. Infrared study of the adsorption of oxygen and carbon monoxide + oxygen mixtures on tin(1V) oxide, and the adsorption of carbon dioxide on ammonia-pretreated tin(1V) oxide, Tin oxide surfaces. Part 9. Infrared study of the adsorption of carbon monoxide, nitric oxide and their mixtures on tin(1V) oxide gels containing ion-exchanged chromium(III), manganese(II), iron(III), cobalt(II), nickel(I1) and copper(II), 2703-1 3 Reversible pyridine-induced formation of superoxide ions labelled with oxygen-1 7, 1324-8 activated strontium oxide, 2763-70 2597-603 STRONTIUM OXIDE Electron paramagnetic resonance study of electron transfer at the surface of alkaline earth oxides.Reflectance spectra of carbon monoxide adsorbed on alkaline earth oxides, 2278-92 Luminescence and other spectrosckpic studies of the reaction of pyridine and kxygen with thermally Photoluminescent spectra of surface states in alkaline earth oxides, 291 3-22 Structural analysis of some molten materials by X-ray diffraction. Part 5. Lithium chloride, lead Nature of solutions of water in sulphuric acid, 2179-92 Heat capacities of hydration of saturated uncharged organic compounds at 25"C, 2408-17 Moderated copolymerization. Part 2.Transfer constant of styryl radicals towards carbon tetrabromide: STRUCTURE chloride and their mixtures, 1861-70 STRUCTURE PROPERTY STYRENE44 J.C.S. FARADAY I SUBJECT INDEX VOL. 74 (1978) a penultimate unit effect in chain transfer, 1020-8 styrene. An unusual decomposition of benzoylperoxide, 1488-95 Influence of applied electric fields on the free radical copolymerization of methylmethacrylate and Vapour pressure measurements on some organic high explosives, 133945 Electromotive force studies of electrolytic dissociation. Part 12. Dissociation constants of some strongly Stability of metal uncharged ligand complexes in ion exchangers. Part 2. The copper + ethylenediamine Moderation of photochemically generated hot hydrogen atoms, 1687-92 Catalyst participation in the reduction of sulphur dioxide by carbon monoxide in the presence of water Oxidation of sulphur dioxide in aerosol droplets, catalysed by manganous sulphate, 2689-702 Solid state reactions of radio sulphur in silver-doped potassium chloride, 2452-9 Electromotive force studies of electrolytic dissociation. Part 12.Dissociation constants of some strongly Nature of solutions of water in sulphuric acid, 2179-92 Bipyridylium quaternary salts and related compounds. Part 6. Pulse radiolysis studies of the reaction of Electron paramagnetic resonance study of electron transfer at the surface of alkaline earth oxides. Photoluminescent spectra of surface states in alkaline earth oxides, 291 3-22 Studies in the system calcium sulphate monohydrate.Part 6. Surface chemistry and porosity of the Surface and electrokinetic potentials of interfaces containing two types of ionizing group, 1179-87 Ionic oxides: distinction between mechanisms and surface roughening effects in the dissolution of Structural characterization of high surface area reduced molybdenum oxide catalysts, 2991-9 Surface tension minimum in ionic surfactant systems, 2501-1 7 Exchange processes in solutions of nitroxide surfactants, 220-2 Light scattering method for the study of close range structure in coagulating dispersions of equal sized Semiconducting oxides: infrared and rate studies of the effects of surface blocking by surfactants in Ionic activities in sodium dodecyl sulphate solutions from electromotive force measurements, 1758-67 Surface tension minimum in ionic surfactant systems, 2501-1 7 Enthalpy of interaction between some cationic polypeptides and n-alkyl sulphates in aqueous solution, Flow equation for coagulated suspensions, 785-94 Kinetics of flowing dispersions.Part 1 1. Dielectric constants of streaming suspensions of spheroids, Heats of mixing and the solid-state transition in ( ( C ~ H ~ ) ~ P C H ~ ) I - ~ +((C~H~)~ASCH~)~ + (TCNQ)r- Kinetics of the reaction between 2,4-dinitrophenol and tri-n-octylamine in chlorobenzene solution. Mutual reaction of isopropyl radicals, 301 6-21 Analysis of activity data in three component systems by means of an augmented Redlich-Kister Study by electron paramagnetic resonance of charge-transfer complexes formed by adsorption of TCNE SUBLIMATION SULPHAMIC ACID ionizing acids at zero ionic strength and 25"C, 1 170-8 complex in montmorillonite and sulphonic acid resin, 182-9 SULPHONIC RESIN SULPHUR SULPHUR DIOXIDE and oxygen, 198 1-9 SULPHUR 35 SULPHURIC ACID ionizing acids at zero ionic strength and 25"C, 1 170-8 SUPEROXIDE paraquat radical analogues with oxygen, 665-75 Reversible pyridine-induced formation of superoxide ions labelled with oxygen-] 7, 1324-8 SURFACE SURFACE AREA calcium sulphate hemihydrates, 1477-87 SURFACE POTENTIAL SURFACE STRUCTURE magnesium oxide, 2907-1 2 SURFACE TENSION SU RFACTANT spherical particles, 733-44 dissolution kinetics, 1624-33 2923-9 SUSPENSION 1242-53 TCNQ TEMPERATURE JUMP (0 x l), anion radical salts, 190-4 Diffusion and other ratelimiting factors, 1804-1 0 TERMINATION TERNARY SYSTEMS formalism, 393-402 TETRACYANOETHYLENEJ.C.S. FARADAY I SUBJECT INDEX VOL.74 (1978) 45 on type X- and Y-zeolites, 530-7 TETRAMETHYLBUTANE TETROXALATE THALLIUM Decomposition of 2,2,3,3--tetramethylbutane in the presence of oxygen, 36679 pH calibration of tetroxalate, tartrate and phthalate buffer solutions at above 100°C, 2434-51 Flame photometric determinations of diffusion coefficients. Part 6. Results for carbon monoxide and On the hydrolysis of silver(II), thallium(II), tin(III), and copper(III), 1820-6 Thallous chloride-thallous sulphide phase diagram, 2 193-9 Very low pressure pyrolysis (VLPP) of 3-chloropropionitrile, 91 2-1 8 Mechanism of ketonization of acetic acid on anatase Ti02 surfaces, 151 7-29 Product crystallite size-reaction rate relationship in M(OH)2--MO decomposition.Structural Evidence for a molecular component in the thermal decomposition of azomethane, 2121-9 Preparation of high surface area reduced molybdenum oxide catalysts, 2982-90 pV-T studies on molten alkali nitrates. Part 1. Thermal pressure coefficients and compressibilities, Freezing points of aqueous alcohols. Free energy of interaction of the CHOH, CH2, CONH and C = C Thermodynamic study of dilute aqueous solutions of organic compounds. Part 5. Open-chain saturated Capillary Phenomena. Part 6. Behaviour associated with the flotation and mechanical manipulation of Transport in aqueous solutions of Group IIB metal salts at 298.15 K. Part 5. Irreversible free atoms of bromine, iodine, and thallium, 715-19 THALLIUM SULPHIDE CHLORIDE SYSTEM THERMAL DECOMPN transformation mechanism, 1530-7 THERMAL PRESSURE COEFFICIENTS 153-62 THERMODN functional groups in dilute aqueous solutions, 1990-2007 bifunctional compounds, 2667-7 1 solid spheres at fluid interfaces, 846-57 thermodynamic parameters for zinc perchlorate and verification of Onsager’s reciprocal relationships, 2885-95 THERMODN FLOTATION THERMODN IRREVERSIBLE THERMODN MIXING Thermodynamics of binary liquid mixtures involving hydrogen bromide, hydrogen chloride and xenon, Thallous chloride-thallous sulphide phase diagram, 21 93-9 Thermal unimolecular reactions of vinylcyclobutane and isopropenylcyclobutane, 1827-33 Mechanism of thermolysis of tetramethylsilane and trimethylsilane, 2171-8 Chlorine kinetic isotope effects.Thermal decomposition of l-chloroethane and evaluation of possible Spectrochemistry of solutions. Part 5. Raman spectroscopic study of the coordination of silver(1) ions in Acidic properties of mixed tin + antimony oxide catalysts, 206-10 Dehydrogenation and isomerization of n-butenes on mixed tin + antimony oxide catalysts, 1590-3 On the hydrolysis of silver(II), thallium(II), tin(III), and copper(III), 1820-6 Protonic conductivity in layered tin chloride dihydrate single crystal, 2333-5 1 Interaction of water molecules with the surface of tin(1V) oxide, 67685 Tin oxide surfaces. Part 4. Infrared study of the adsorption of oxygen and carbon monoxide + oxygen mixtures on tin(1V) oxide, and the adsorption of carbon dioxide on ammonia-pretreated tin(1v) oxide, 2597-603 Tin oxide surfaces.Part 8. Infrared study of the mechanism of formation of a surface isocyanate species on tin oxide - 0.55 copper oxide during catalysis of the oxidation of carbon monoxide by nitric oxide, 2604- 16 Tin oxide surfaces. Part 9. Infrared study of the adsorption of carbon monoxide, nitric oxide and their mixtures on tin(1V) oxide gels containing ion-exchanged chromium(III), manganese(II), iron(III), cobalt(II), nickel(I1) and copper(II), 2703-1 3 893-9 1 1 THERMOLYSIS models of activated complex, 2714-23 liquid ammonia by thiocyanate ions, 432-9 THIOCYANATE TIN TIN CHLORIDE DIHYDRATE TIN OXIDE TNT Vapour pressure measurements on some organic high explosives, 1339-45 Gas-liquid chromatographic studies of thermodynamic interactions in ternary systems comprising dinonylphthalate + trinitrotoluene + volatile hydrocarbon, 1655-65 TRANSERENCE NUMBER Velocity correlation coefficients as an expression of particle-particle interactions in (electrolyte) solutions 933-4746 J.C.S.FARADAY I SUBJECT INDEX VOL. 74 (1978) TRANSFER TRANSFER KINETICS Free energies and entropies of transfer of ions from water to methanol, ethanol and 1-propanol, 2101-10 Kinetic analysis of deuteron-transfer reactions of alkylamidines with (2H2)4nitrophenylnitromethane. Free energies and entropies of transfer of ions from water to methanol, ethanol and I-propanol, 2101-10 Transference numbers of a 2:2 electrolyte: magnesium sulphate in water at 25" C, 1036-44 Kinetics of the decomposition and hydrogen reduction of nitric oxide on niobium, nickel and platinum filaments at high temperatures and low pressures, 21 1-19 Patterns of activity in the benzene-deuterium exchange reaction and the hydrogenation of benzene catalysed by evaporated metal films, 1666-75 Chemical energy accommodation at catalyst surfaces.Flow reactor studies of the association of nitrogen atoms on metals at high temperatures, 1883-912 Effect of lead compounds on heterogeneous oxidation catalysts, 1922-38 Tin oxide surfaces. Part 9. Infrared study of the adsorption of carbon monoxide, nitric oxide and their mixtures on tin(1V) oxide gels containing ion-exchanged chromium(III), manganese(II), iron(III), cobalt(II), nickel(I1) and copper(II), 2703-1 3 coefficients for cadmium-I 15 ions in aqueous cadmium iodide, 93-102 thermodynamic parameters for zinc perchlorate and verification of Onsager's reciprocal relationships, 2885-95 thermodynamic parameters for zinc chloride and verification of Onsager's reciprocal relationships, 2896-906 Implications of isotopic scrambling for the determination of kinetic isotope effects, 1254-62 TRANSFER THERMODN TRANSFERENCE NUMBER TRANSITION METAL TRANSPORT PROCESS Transport in aqueous solutions of Group IIB metal salts (298.15K).Part 3. Isotopic diffusion Transport in aqueous solutions of Group IIB metal salts at 298.15 K. Part 5. Irreversible Transport in aqueous solutions of Group IIB metal salts at 298.15 K. Part 6. Irreversible TRANSPORT PROPERTY TRANSPORT THEORY Velocity correlation coefficients as an expression of particle-particle interactions in (electrolyte) solutions Heats of hydrogenation of large molecules.Part 3. Five simple unsaturated triglycerides Recoil tritium reactions with methylsilane43: pressure dependent yields, 8 18-26 Kinetic isotope effect in the reaction of 4nitrophenylnitromethane with pentamethylguanidine in Heterocoagulation. Part 3. Interactions of polyvinyl chloride latex with Ludox HS silica, 1346-59 Heats of hydrogenation of large molecules. Part 2. Six unsaturated and polyunsaturated fatty acids, Absorption spectra of radical ions of polyenones of biological interest, 538-45 Effect of temperature on the acid dissociation constants of 1, 10-phenanthroline and some related bases in water, 1075-80 Spectrophotometric investigations of aqueous solutions at elevated temperatures.Effect of temperature on the stability constants of the tris complexes of l,l&phenanthroline, 5-nitrc~l ,l&phenanthroline and 2,2'-bipyridyl with iron (11), 1081-8 Flash photolysis study of the spectra of methyl peroxy and tert-butyl peroxy radicals and the kinetics of their mutual reactions and with nitric oxide, 1693-701 Self-reactions of isopropylperoxy radicals in the gas phase, 2293-300 Surface properties and catalytic activity of a molybdenum-fixed catalyst. Structure of the active site and Spectroscopic investigation of the structure of a novel zerovalent cobalt nitrosyl in zeolite matrixes, Reflectance spectra of carbon monoxide adsorbed on alkaline earth oxides, 2278-92 pV-T studies on molten alkali nitrates. Part 2.Internal energies and equation of state, 163-73 Vapour pressure measurements on some organic high explosives, 1339-45 Velocity correlation coefficients as an expression of particle-particle interactions in (electrolyte) solutions 933-47 TRIGLYCERIDE (triacylglycerols), 2868-72 TRITIUM TUNNELLING toluene, 1263-7 TYNDALL EFFECT UNSATD ACID 46-52 uv mechanism for selective oxidation of ethyl alcohol, 2968-8 1 3000-7 UV REFLECTION VAN DER WAALS EQUATION VAPOUR PRESSURE VELOCITY CORRELATION COEFF 933-47J.C.S. FARADAY I SUBJECT INDEX VOL. 74 (1978) 47 VINYL Polymerization of vinyl monomers initiated by chromium(I1) acetate + organic peroxides, 1726-37 Living radical polymerizations of vinyl monomers initiated by aged chromium(I1) + BPO in Aqueous solutions containing amino acids and peptides. Part 8. Gibbs free energy of interaction of homogeneous solution, 1738-49 some cqco-amino acids with sodium chloride at 298.15 K, 2779-85 VIRIAL VISCOELEC COEFF Viscoelectric coefficient for water, 450-5 Viscosity and conductance studies in ethylene carbonate at 40°C, 2070-6 VISCOMETRY VISCOSITY Structure of aqueous solutions. Infrared librational band study of structure making and structure Flow equation for coagulated suspensions, 785-94 Effect of viscosity on the bimolecular termination rate constants for semiquinone radicals in solution: a Partial molar volumes and viscosity of benzene solutions of tertiary n-alkylammonium picrates, 21 59-65 breaking by dissolved electrolytes, 583-96 kinetic ESR study, 21 11-20 VISIBLE SPECTRA On the hydrolysis of silver(II), thallium(II), tin(III), and copper(III), 1820-6 VOLTAMMETRY Temperature and pressure effects on surface processes at noble metal electrodes. Part 2. Volume of Physical adsorption of gas mixtures of 2,24imethylpropane and n-butane on Vycor glass and on Resonance Raman spectra of carbonium ions adsorbed on porous Vycor glass, 1562-8 Washburn numbers. Part 3. Alkali-metal chlorides in the DMSO + water svstem: comr>arison with adsorbed hydrogen and oxygen species at platinum and gold, 1390-402 spherisorb silica, 948-59 WCOR WALDEN PRODUCTS - , I hydrochloric acid; structural effects, 380-92 WALL PROCESSES Rate constants for the removal of radicals at the wall in linearly branched or terminated chain reactions, Washburn numbers. Part 3. Alkali-metal chlorides in the DMSO + water system; comparison with Viscoelectric coefficient for water, 450-5 Structure of aqueous solutions. Infrared librational band study of structure making and structure Interaction of water molecules with the surface of tin(1V) oxide, 676-85 Free energies and entropies of transfer of hydrogen halides from water to aqueous alcohols and the Some properties of binary aqueous liquid mixtures. Apparent molar volumes and heat capacities at 298. Dielectric properties of water adsorbed by kaolinite clays, 1221-33 Adsorption of water vapour by silica and the effect of surface methylation, 1360-72 Self-diffusion coefficients of water in pure water and in aqueous solutions of several electrolytes with Competitive preferential solvation theory of weak molecular interactions, 221 0-28 Correlation of the catalytic activities of oxides with their work functions. Recombination of oxygen Structural analysis of some molten materials by X-ray diffraction. Part 3. Manganese dichloride, 804-8 Structural analysis of some molten materials by X-ray diffraction. Part 5. Lithium chloride, lead X-ray photoelectron spectroscopy study of palladium and platinum ions in type Y-zeolite. Electron 765-75 WASHBURN NUMBER hydrochloric acid; structural effects, 380-92 WATER breaking by dissolved electrolytes, 583-96 structure of aquo-organic solvents, 105143 15 K over the whole mole fraction range, 1 159-69 oxygen-18 and deuterium as tracers, 1879-81 WEAK MOL INTERACTION WORK FUNCTION atoms on lithium(1 +) doped nickel oxides, 1750-7 X RAY DIFFRACTION chloride and their mixtures, 186 1-70 transfer between metal aggregates and the support as evidenced by X-ray photoelectron spectroscopy and electron spin resonance, 440-9 Thermodynamics of binary liquid mixtures involving hydrogen bromide, hydrogen chloride and xenon, Surface properties and catalytic activity of a molybdenum-fixed catalyst. Structure of the active site and X RAY PHOTOELECTRON SPECTROSCOPY XENON 893-91 1 X P S mechanism for selective oxidation of ethyl alcohol, 2968-8 148 J.C.S. FARADAY I SUBJECT INDEX VOL. 74 (1978) ZEOLITE Site group interaction effects in zeolite-Y. Part 1. Structural examination of the first stages of the silver Site group interaction effects in zeolite-Y. Part 2. Sodium-silver selectivity in different site groups, Active centres on sodium hydrogen-Y zeolite in but-l-ene transformations, 146-52 Adsorption of ethane and ethylene by zeolites MgNaX and CaNaX with different degrees of ion X-ray photoelectron spectroscopy study of palladium and platinum ions in type Y-zeolite. Electron Location of cations in synthetic Zeolites-X and -Y. Part 5. The cation distribution in calcium-Y, Location of cations in synthetic zeolites-X and -Y. Part 6. Influence of X-ray irradiation on the Study by electron paramagnetic resonance of charge-transfer complexes formed by adsorption of TCNE Percolation of gases into (potassium, calcium)-A zeolites and their cation distribution, 6 13-21 Transition metal ion exchange in zeolites. Part 3. Ternary exchange in mordenite involving ammonium, Intercrystalline molecular transport in zeolites studied by uptake experiments and by nuclear magnetic Isomerization of n-butenes on A-type zeolites studied by infrared spectroscopy. Part 1. n-Butene Comparative study of the hydrogen reduction of nickel(I1) ions in X- and Y-zeolites, 1 5 3 8 4 Characterization of the hydroxyls in offretite zeolite, 1786-95 Sorption behaviour of silanated H-mordenite, 187 1-8 Carbonylation of methanol and ethanol on a rhodium-zeolite catalyst, 23 13-19 Model for analysing diffusion in zeolite crystals, 2423-33 Adsorption and polymerization of acetylene on oxide surfaces. A Raman study, 2542-9 Complexes of ammonia and ethylenediamine with copper(I1) on zeolite A, 2550-61 Infrared study of carbon monoxide chemisorption on zeolite and alumina supported rhodium, 2570-80 Modified zeolites. Part 1. Dealuminated mordenites and their silanation, 2786-97 Modified zeolites. Part 2. Sorption by dealuminated, silanated mordenites, 2798-806 Spectroscopic investigation of the structure of a novel zerovalent cobalt nitrosyl in zeolite matrixes, Colloid stability in butanol, 2271-7 Interaction of oxygen with zinc surfaces, 869-82 Kinetics and mechanism of fast metal-ligand substitution processes in aqueous and micellar solutions Transport in aqueous solutions of Group IIB metal salts at 298. I5 K. Part 6. Irreversible ion exchange, 13 1-5 136-45 exchange, 306-1 5 transfer between metal aggregates and the support as evidenced by X-ray photoelectron spectroscopy and electron spin resonance, 440-9 calcium-X and lanthanum-Y in the ultimate stages of dehydration, 466-76 location of exchangeable cations, 477-83 on type X- and Y-zeolites, 530-7 triethanolammonium and complexed nickel(II), 745-55 resonance pulsed field gradient techniques, 1210-20 adsorption on zeolites containing alkali and alkaline earth cations, 1435-43 3000-7 ZETA POTENTIAL ZINC studied by means of a dye-laser photochemical relaxation technique, 2625-36 thermodynamic parameters for zinc chloride and verification of Onsager’s reciprocal relationships, 2896-906 ZINC OXIDE Effect of oxygen chemisorption and photodesorption on the conductivity of zinc oxide powder layers, 3 1-45 Flow equation for coagulated suspensions, 785-94 Electron spin resonance studies of the formation and thermal stability of oxygen radicals on calcium Chemical processes at clean (10-10) zinc oxide surfaces. Part 1. Thermal production of surface defects, Transport in aqueous solutions of Group IIB metal salts at 298.15 K. Part 5. Irreversible ZINC CHLORIDE oxide and some other oxides, 883-92 2724-4 1 ZINC PERCHLORATE thermodynamic parameters for zinc perchlorate and verification of Onsager’s reciprocal relationships, 2885-95

ISSN:0300-9599    

DOI:10.1039/F197874BA001

出版商:RSC    

年代:1978

数据来源: RSC

摘要:

Micellar Catalysis of Metal-Complex Formation Kinetics of the Reaction between Ni" and Pyridine-2-azo-p-dimethylaniline (PADA) in the Presence of Sodium Dodecylsulphate Micelles ; a Model System for the Study of Metal Ion Reactivity at Charged Interfaces. BY ALAN D. JAMES~ AND BRIAN H. ROBINSON" Chemical Laboratory, University of Kent at Canterbury, Kent CT2 7NU Received 20th December, 1976 The kinetics of the reaction between Ni2+(aq) and the bidentate ligand pyridine-2-azo-p-dimethyl- aniline have been investigated in sodium dodecylsulphate micellar solutions. Considerable catalysis effects (up to lo3) are observed on the rate of complexation. The rate dependence on pH and micelle concentration can be quantitatively explained, the former in terms of the surface potential of the micelle.The reaction occurs in the region of the micelle surface, over the detergent concerrtration range studied, and rate constants appropriate to a surface reaction are derived. The catalysis effect resides in the concentrative effect of the micelle surface on the reagents, since the rate of water loss from Niz+ at the surface of the micelle is little changed from that in bulk water. The effect of added electrolyte on the micelle-catalysed rate has also been investigated. . Much of the interest in micelle-catalysed reactions arises from structural similarities between micelles and globular enzymes, and to parallels between micellar and enzyma- tic catalysis. Although micellar catalysis of organic reactions in aqueous media' has been much studied in recent years,l* relatively little work has been reported involving inorganic reactions. In biological systems, ligand exchange with metal ions often occurs at interfaces, so that the reactivity of metal ions towards ligand exchange in such an environment and the effects of the interface on the overall rate processes are of fundamental importance from both a biochemical and physicochemical viewpoint. A convenient specific reaction for study is that between Ni" and the bidentate nitrogen ligand pyridine-2-azo-p-dimethylaniline (PADA), (1).This reaction has been previously studied in aqueous solution,3* aqueous-alcohol mixtures and in dipolar aprotic solvents.6 The rate-limiting step of the reaction in water is the loss of water from the inner coordination sphere of Ni2+, following rapid formation of an .outer-sphere complex, 3* (Subsequent ring-closure is generally rapid in aqueous solution.) The rate of loss of water is identified with the rate of solvent-exchange p Present address : Akzo Chemie U.K. Ltd, Stockpit Road, Kirkby Industrial Estate, Liverpool L33 7TH. 10A. D. JAMES AND B. H. ROBINSON 11 (ke3 as measured by n.m.r. methods. This mechanism is known as the Eigen- Wilkins mechani~m.~ N kex N fast outer-sphere k b inner-sphere N N Kos [Ni(H20),I2+ + N) + [(H20),NiOH2N)]2+ + [(H20)4Ni )I2+. complex slow complex For [Ni2+] 9 [PADA], and KO, Q [Ni'+]-', scheme (1) leads to eqn (2) kobs = Kosk,[Ni2+] + k b (2) where is the equilibrium constant for outer-sphere complex formation, ke, is the first-order rate constant for water loss, and kobs is the observed first-order rate con- stant for metal complex formation (= +).In this paper, we report factors which influence the kinetics of the reaction between the aquonickel ion and PADA in the presence of micellar sodium dodecyl (lauryl) sulphate. The reaction is related to the incorporation of metal ions into porphyrins, which has been studied both in micelles * and microemulsions.g EXPERIMENTAL Ni(NO&. 6Hz0, Na2HP04, NaH2P04 and NaOH were AnalaR grade. PADA was supplied by Sigma Chemicals and 4-dimethylanilinoazobenzene (dimethyl yellow, 2) by Hopkin and Williams. Sodium lauryl sulphate (SLS) was B.D.H. specially pure grade (> 99 %) and was used without further purification. Potassium polyvinylsulphate was supplied by Eastman Kodak, Triton X-100 (iso-octylphenoxypolyethoxylethanol containing approximately 10 mols of ethylene oxide) by B.D.H., sodium methylsulphate by Hopkin and Williams and tetraethylammonium chloride by Aldrich Chemicals.mol dm-3) and PADA solution mol dm-3) were mixed in a small-volume stopped-flow apparatus designed and built in this laboratory. Additional reagents (SLS, buffer, inert salt) were added to the PADA solution before mixing with the Ni2+ solution. Identical results were obtained when micellar solutions containing nickel were mixed with the same concentration of micelles containing PADA, i.e., the micelle concentration was not changed on mixing. However, when PADA was not equilibrated with micellar SLS before mixing with the Ni2+ solution, i.e., when the Ni2++ micelle solution was mixed with PADA, non- exponential traces were obtained.This is consistent with our earlier observations, which show that dye absorption can be a relatively slow process, requiring several hundred milli- seconds for completion.1° All the data reported here refer to solutions in which PADA was equilibrated with SLS before mixing with NiZ+ and where the final concentration of SLS after mixing is always greater than the critical micelle concentration (c.m.c.). First order rate constants (/cobs) or relaxation times (7) were obtained from changes in transmittance at 460 or 550 nm, and the values quoted are the average of five runs under identical conditions. When mi2+] > [PADA], good exponentials were obtained and the derived average first-order rate constants (7-l) are accurate to The pK, values of PADA and dimethyl yellow in the presence and absence of SLS micelles were obtained from spectrophotometric pH-titrations on a Unicam SP8000 spectro- photometer ; the accuracy is estimated as k0.05 units. Sodium hydrogen phosphate buffers were preferred to collidine or lutidine buffers, because the latter may bind hydrophobically to the micelle surface region and interact more strongly with Ni2+ in that state.Binding of phosphate to Ni2+ at the concentration of buffer em- ployed (5 x mol dm-3) is negligible. The pH of the mixed solution was checked using a Radiometer pH meter 26 after collecting the effluent from the stopped-flow drain tube. For the kinetic runs, equal volumes of Ni(N03)2 solution (> 5 x 5 %.RESULTS The visible absorption spectra of PADA, PADAH+, and NiPADA2+ are shown in fig. 1. There is a slight bathochromic shift ( - 3 nm) of the PADAH+ peak on binding12 MICELLAR CATALYSIS OF METAL COMPLEX FORMATION to the micelle, but the spectrum of PADA is hardly changed in the presence of SLS micelles. When Ni(NO& solutions were mixed with PADA solutions containing SLS at concentrations (after mixing) greater than the c.m.c., there was an exponential forma- tion of NiPADA2+, which could be detected from measurements at both 460 and 550nm. The magnitude and direction of the relaxation amplitudes at both wave- lengths were as expected from the spectra in fig. 1. Hence at high pH, there was a decrease in absorbance at 460 nm and an increase at 550 nm, whereas at low pH there was a decrease in absorbance at both wavelengths, with the amplitude at 460 nrn decreasing sharply as the pH was lowered.450 500 550 600 A/nm FIG. 1.-Spectra of PADA (A), PADAH+ (B) and Ni(PADA)2+ (C) in aqueous micellar solution. ([SLS] = 0.025 mol dm-3) In the absence of surfactant, the rate of reaction decreases as the pH is reduced from 8.0. At constant concentration of Ni2+(aq), the pH profile [fig. 2(a)] shows an inflexion around a pH of 4.5, which is close to the spectrophotometrically measured PKa of PADAH+ in bulk water. In the presence of micellar SLS, there is a consider- able rate enhancement [fig. 2(b),(c)]. The pH profiles are of similar appearance, but the inflexions occur at higher pH, in the region of 6.2-6.8, depending on the con- centration of SLS.The pKa of PADAH+ in 0.025moldm-3 SLS was measured independently by spectrophotometric titration and found to be 6.55, in agreement with that obtained kinetically (6.70) at 298.2 K. At fixed concentrations of Ni2+(aq) and pH, z-l (or kobs) decreased as the con- centration of micellar surfactant increased. The rate of reaction is, therefore, greatest just above the cmc of SLS. 7-l also increases in an approximately linear way with increase in pi2+] at a particular pH and SLS concentration. These effects are shown in fig. 3.A. D. JAMES A N D B. H. ROBINSON 13 Non-micelle-forming sodium methylsulphate (0.5 mol dm-3), which was added as a possible complexing agent for Ni2+, and potassium polyvinylsulphate, a linear polyelectrolyte, have little catalytic effect on the rate.Triton X-100, an uncharged surfactant with a hydroxyl terminal head-group causes a decrease in rate (table 1). b 1.5 1 .o 0.5 3 4 5 6 7 PH FIG. Z(u).-pH profile for the reaction in the absence of surfactant. [Ni2+] = mol dm-3, T = 298.2 K. [The solid line is a theoretical line calculated from eqn (lo)]. Addition of up to 0.1 mol dm-3 NaCl causes a modest decrease in the catalysed rate for an SLS concentration of 0.025 mol dm-3, but a much greater decrease is obtained with tetraethylammonium chloride (fig. 5) at the same surfactant concentration. An activation enthalpy of 52.3 (f4) kJ mol-' was obtained from the temperature dependence of 2-l over the range 20-40°C for the complex formation reaction at 30 20 10 4 5 6 7 8 9 150 50 FIG.P H 2(b),(c).-pH profile for the reaction in the presence of micelles. [Ni2+] = mol dm-3, T = 298.2 K. (b) = 0.025 rnol d r 3 SLS, (c) = 0.10 mol dm-j SLS.14 MICELLAR CATALYSIS OF METAL COMPLEX FORMATION [SLS] = 0.1 mol dm-3, [Ni2+] = mol dm-3, and pH = 7.5-8.5. (The c.m.c. of SLS does not change significantly over this temperature range.) This compares with a value of 55.2( & 4) kJ mol-1 measured in bulk solution for the same pro~ess.~ The equilibrium constant for complex formation ( K l ) in the presence of micelles at pH - 8 can be measured from the absorbance at 460 and 550 nm, and the total concentrations of Ni2+ and PADA. However, Kl is so high that, with the condition [SLS]/mol dm-3 FIG. 3.-Dependence of the reaction rate on [SLS].(T = 298.2 K.) (a) [Ni2+] = rnol dnr3, pH = 7.5-7.7; (b) [Ni2+] = 3.3 x rnol dm-3, pH = 7.3-7.5 ; (c) [Ni*+] = mol dm-’, pH = 8.0. [Ni2+] 9 [PADA], the absorbance changes are negligibly small in 1 cm optical cells. If we use similar concentrations of the two reactants, the results are best rationalised by allowing for formation of a bis-complex with equilibrium constant K2. A best fit to the equilibrium data is obtained when Kl - K2. Therefore, under the condi- tions of the kinetic runs, when mi2+] 9 [PADA], no bis-complex will be formed. TABLE 1 .-EFFECT OF ADDITIVES ON THE RATE OF COMPLEX FORMATION AT 298.2 K. [PADA] = 2 x mol dm-3 additive none 0.5 mol dm-3/sodium methyl sulphate 0.5 mol dm-3/sodium methyl sulphate 0.01 mol dm-3/polyvinylsulphate anion 0.01 mol dm-3/polyvinylsulphate anion 1 % w/w Triton X-100 1 % w/w Triton X-100 [NiZ+]/mol dm-3 10-3 10-3 5~ 10-3 10-3 5~ 10-3 10-3 5 x 10-3 T-l/S-* 1.4 1.1 5.2 0.6 3.6 0.25 0.9 Qualitatively, we find that the “ apparent ” equilibrium constant Kl ( = [NiPADA2+]/[Ni2+][PADA]) for the reaction in the presence of micelles decreases with increasing SLS concentration above the c.ni.c.tending towards the bulk value at high SLS concentrations. The equilibrium therefore provides a very sensitive indicator of the c.m.c. at - 8 x mol dm-3. Kl - lo5 dm3 mol-l when [SLS] = 0.2 molA. D. JAMES AND B. H. ROBINSON 15 dm-3, compared with a value of 1.3 x lo4 dm3 mol-l in the absence of surfactant (data at 298 IS). MECHANISM OF THE REACTION The pH profile [fig.2(a)] is consistent with the following kinetic scheme : k i Ni2++PADA + NiPADA2+ k- 1 k2 K,: Jr H+ (3) Ka Jt' H+ Ni2+ + PADAH+ + NiPADAH3+. k- 7 Proton-transfer is rapid in the presence of buffer. We also have the condition [N~"]T 9 [PADAIT, where T indicates the total or weighed-in concentration per dm3 of solvent. We define : [NiPADA2 '1 [H ' ] [NiPADAH3+] * and KL = [ PADA] [ H'] [ PADAH'] K , = - (4) Then the general relaxation expression ( 5 ) can be derived It is useful to derive experimental conditions. but is much less reactive from first principles the kinetic equations relevant to our Below pH 8.0, PADAH+ becomes kinetically significant, towards Ni2+ than PADA, so we have : kl k- 1 Ni2++PADA + NiPADA2+ PADAH+ Ka 11 H+ d[NiPADA2+]/dt = kl [Ni2+]CpADA] - k-1[NiPADA2+] [PADAIT = [PADA] + [PADAH+] + [NiPADA2+].(7) (8) (9) (10) (1 1) Therefore PADA] = ([PADA],- [NiPADA2+])/(1 + K: '[H+]). 7-l = [Ni2+lT(kl/(l +KL1[H+])} +k-,. 2-1 = k , [Ni2+IT + Ll. It follows, on integration for constant [Ni2+] and [H+], that : At high pH when [H+] < Ka, At low pH when [H+] 9 K,, the complete expression (5) must be used. Eqn (10) gives a reasonable fit to the kinetic data obtained in the absence of SLS [fig. 2(a)], with pKa = 4.5, k-l = 0.1 s-l and kl = 1.25 x lo3 dm3 mol-1 s-l. This latter value is in excellent agreement with the previously reported value of (1.35 kO.11) x lo3 dm3 mol-1 s - , . ~ The above kinetic treatment (5)-(10) can be also applied ta the reaction in the presence of micellar SLS, if appropriate values of the Ni2+ concentration and Ka are employed.In micellar solutions, there is an apparent increase in the PKa of PADA of - 2 units, as measured by spectrophotometric titration, because PADA and PADAHf16 MICELLAR CATALYSIS OF METAL COMPLEX FORMATION are located close to the surface of the micelle. The surface PKa of the ligand, (pK,),, is related to the bulk pK, by eqn (12), originally due to Hartley l2 At 298.2 K, (pKa)s-pKa = $159.2. (12) In eqn (12), II/ is the surface potential of the micelle in mV. Values of $, from eqn (12), for PADA and the structurally similar dye dimethyl yellow (2) in 0.025 mol dm-3 SLS are in good agreement. Values of $ obtained from pH-titrations of dimethyl TABLE 2.-vALUES OF “APPARENT” ACID DISSOCIATION CONSTANTS OF DIMETHYL YELLOW AND PADA IN MICELLAR SOLUTIONS.T = 298.2 K. [SLS]/mol dm-3 pL(dimethy1 yellow) PKs(PADA) - 3.35 - 4.5 0.025 5.42 6.55 0.125 5.46 6.59 0.050 5.15 6.28 a 0.10 5.02 6.15 a 0.20 4.85 5.98 a 0 Obtained by comparison with data for dimethyl yellow. yellow had already been measured l3 and were, therefore, used in eqn (12) to derive (PK,)~ values for PADA in the presence of various concentrations of SLS and additives (tables 2 and 3). Values of $ obtained using dimethyl yellow are in satisfactory agreement with those obtained from electrophoretic measurements l4 (table 3) ; this strongly suggests that the major influence on (PKa), is due to the increased hydrogen ion concentration close to the micelle surface, rather than an effect on the intrinsic TABLE 3 . v A L U E S OF “HE SURFACE POTENTIAL AND AREA PER HEAD GROUP AT DIFFERENT SALT CONCENTRATIONS ~aCl]/mol dm-3 ~t4NCl]/mol dm-3 w/(mV)O tp/(mV)b .4/10-16 cm2 C 0 0 0.025 0.050 0.075 0.10 0 0.0125 0.025 0.050 0.10 124 149 61 96 99 58 89 88 55(0.5) 86 82 54(0.2) 84 80 53 63 27 12 6 a From eqn (12) using @K& of dimethyl yellow.b From the electrophoretic data in ref. (14) by interpolation. C Area per head group from ref. (20) ; head group area in closed packed monolayer = 45 x cm2 ref. (21). PKa of the dye, arising from the change in en~ir0nment.l~ In the absence of added inert salt, [H+Is N 10O[H+lb, where [H+], refers to the hydrogen ion concentration at the micelle surface. For the reaction in the presence of micelles, (pK,), must be used in eqn (5) and (10), where [H+] in these equations still refers to the bulk concentration (measured using a glass electrode).The use of these values of ( p Q S is consistent with the inflexion point determined from the plot of 7-l against pH in the presence of micelles [fig 2(b) and (c)].A. I). JAMES AND B. H. ROBINSON 17 The other important consideration in micellar systems is how to express [Ni2+IT. We suppose, in the absence of added NaCl, that all the Ni2+ is contained within the surface region of the micelle, predominantly in the outer Helmholtz layer (Stern layer), but with an intact solvation shell, i.e., within a distance of N lo-’ cm from the surface. It is, therefore, the surface concentration of Ni2+ which is kinetic- ally important. A simple way to express this concentration is by the dimensionless quantity [Ni2+IT/(C-c.m.c.) where Cis the weighed-in SLS concentration and c.m.c.= 8 x mol dm-3 at 25°C in the absence of added electrolyte.16 (This expression is obviously inapplicable for SLS concentrations close to the c.m.c.) Then it follows that, as the micelle concentration is increased, the nickel ion will be diluted on the surface, and the variation of 2-l with surfactant concentration can be explained (fig. 3). 150 100 vl ?, L \ $4 50 FIG. 4.-PIot of T- I / I 0.02 0.04 Y 0.06 against [Ni2+]~/(C-c.m.c.){ 1 + (K&-’[H+ }T= Eqn (10) then becomes (13), for the micelle-catalysed reaction. 2-l = k’lCNi”’I,/((C-c.m.c.)(I +(K,)F ‘[H+])) + k’_ 1. 98.2 K. Fig. 4 shows a plot of 2-l against [Ni2+],/(C-c.m.c.){l +(Ka)F1[H+J)) over a wide range of H+, Ni2+ and SLS concentrations, from which we find ki = 3000 S-l.The fact that a reasonable linear plot is obtained is excellent evidence in support of the proposed mechanism. From the dependence of r1 on mi2+] at low pH, and using the value of k i obtained at high pH, k$[= k,/(C-c.m.c.)] can be obtained as 11 s-l. In principle, kL1, the rate constant for the reverse reaction on the micelle surface, could be obtained as the intercept as [Ni2+] 3 0 at high pH [eqn (1 l)], but in practice the reaction goes to completion when [Ni2+] % [PADA]. An intercept of 0.4 s-l was obtained at pH 4.2 but it may contain contributions from both kLl and kL2, depending on the value of (pK& [eqn (5)]. The mechanism predicts that a limiting rate will be reached when the surface becomes saturated with nickel, since no diffusion is then required for reaction.The kinetics are then determined by some first-order process which might be water loss from the inner coordination sphere of nickel (kex), or ring-closure to form the bidentate complex, if this were sterically-hindered on the surface. Alternatively the slowest18 MICELLAR CATALYSIS OF METAL COMPLEX FORMATION process might be diffusion of PADA from an unreactive position in the micelle interior to the micelle surface. A refinement of eqn (13) is to express the surface concentration of Ni2+ in terms of the restricted volume available to the ion close to the micelle surface. If the ion is confined to within a distance r cm from the surface (but in the solvent) and A is the surface area (cm2)/surfactant head group at the surface : molar.[Ni2'IT. 1000 (C - c.m.c.)N,,Ar [Ni2'Is = ~ Thus we might expect that the rate would be affected by changes in structural pro- perties of the micelle, e.g., by the effect of temperature and ionic strength on the head group area. DISCUSSION The plot shown in fig. 4 provides good evidence that the reaction occurs in the region of the micelle surface. It is clearly the surface concentrations of H+, Ni2+ and PADA which are kinetically important. A similar value of z-l is obtained at a particular value of [Ni2+]/(C-c.m.c.) at both low (0.0125 mol dm-3) and high (0.1 mol dm-3) SLS concentrations, which implies that all the Ni2+ (and PADA) is bound to the micelle. Otherwise, as the SLS concentration is increased, more binding of Ni2+ would result, resulting in an increase in 7-l at a particular value of [Ni2+]/ (C-c.m.c.).This conclusion is supported by n.m.r. studies on Mn2+ binding to SLS micelle~,~~ and electrophoretic studies on SLS in the presence of various divalent metal i0ns.I The enhanced rate of reaction between Ni2+ and PADA in the presence of micellar SLS may be due to : (i) An effect on the frequency of water loss (kex) from the inner coordination sphere of Ni2+. (ii) The concentrative effect of the micelle on the reactants. (iii) An increased interaction in the outer-sphere complex on the surface of the micelle. By analogy with the behaviour of Mn2+,17 ke, is not expected to be greatly en- hanced by adsorption on the micelle surface. The similarity of the measured AH:, values in the presence and absence of SLS also supports this conclusion. Data available for rates of water exchange about divalent metal ions l9 show that the variation in rate is controlled by AH;.Although k,, may vary from 90 to 8.0 x lo9 s-l on going from V2+ to Cr2+, the factor affecting the rate of exchange is always AH,',, AS& being more or less constant and close to zero. For Ni2+(aq), k,, = 3.0 x lo4 s-l, AH& = 46.8 kJ mol-1 and AS,", = 4.2 J K-l mol-l. Since water loss is rate limiting in aqueous solution (rather than ring-closure), the similarities in the activation enthalpies suggest that water loss is also rate limiting on the surface. From eqn (13) and (14), we can derive [expression (15)] a second-order rate con- stant kl for the surface reaction which is directly comparable with that in bulk solution.kl = k;N,Jr. Using eqn (15) and taking ki = 3000 s-l, A = 60 x cm2 2o (table 3) and r = cm, we obtain kl = 1.1 x lo3 dm3 mol-1 s-1 for complex formation on the surface, similar to that measured in bulk solution of 1.25 x lo3 dm3 mol-1 s-l. This result very strongly suggests that catalysis is largely due to a concentrative effect of the micelle surface. Unless (k& and (KO& change in a compensatory way (unlikely for unrelated processes), we must conclude that the water exchange rate for nickel (II)A. D. JAMES AND B. H. ROBINSON 19 at the micelle surface has a similar value to that in the bulk solvent. At constant [Ni2+IT, therefore, we can write : total volume of reaction medium volume available for Ni2+ at the surface' - - (7- l)SLS ( z - ~ ) H ~ O Since it has now been established that the reaction is not catalysed by lowering of the activation energy barrier for the reaction, but only by concentrating the reagents in a small part of the total reaction volume in the region of the micelle surface, it is convenient to express the rate constant for the complexation reaction ki in the manner applicable to a surface reaction.The surface concentration of Ni2+ expressed as (moles of Ni2+)/(area of micelle surface available) is given by : [Ni2+lB [Ni2']: = mol cm-2 (C - c.m.c.)BAN,v where B refers to bulk concentrations in mol (dm3 of solution)-l. solvent, and surface concentrations are used in defining K& ; Then, for [Hf] < (Ka)s, using eqn (13) and (15): For the reaction at the surface, if the same mechanism operates as in the bulk (17) k; = KLsk:x cm2 mol-' s - k; = k;N,,A 1.1 x 1013 cm2 mol-l s-l.For outer-sphere complex formation between Ni2+ and PADA on the surface of the micelle, assuming that the PADA is tightly bound to the micelle, we can easily calculate (by analogy with the Fuoss Equation) that K& = (4nNava2/2) exp ( -AGint/RT) cm2 mol-1 where a is the distance of closest approach of the reactants on the surface (Ni2+ solvated) and AGint represents the difference in free energy between the nickel ion interacting with a surface site containing PADA compared with a surface made up of negatively-charged sulphate head groups. If we assume a = 4 x lo-' cm, and AGint = +4.0 kJ mol-l (since the outersphere site is less favoured on coulombic arguments) then Kis = 1.2 x lo9 cm2 mol-' and kix - lo4 s-' which is again in very close agreement with that measured in bulk water. This general conclusion might be expected since the loss of water is controlled more by ion-dipole and ligand-field interactions than by structural effects in the solvent near to the mimlle surface.Further experiments are now being carried out to determine to what extent this conclusion can be generalised. The effect of electrolyte (NaCl and (C,H,),NCI) is to cause a decrease in the catalysed rate (fig. 5). Addition of NaCl decreases the surface potential and changes the shape of the micelle from spherical to ellipsoidal so that the surface area per head group (A) is decreased (table 3).20 The decrease in $ (due to an increase in the extent of Na+ binding) will lead to desorption of Ni2+, resulting in a decrease in the rate of reaction as observed.However, the accompanying decrease in the surface area per head group, (table 3), would lead to an increase in 7-l of up to 15 %. The effect of NaCl on 2-l is a balance of these opposing factors.20 MICELLAR CATALYSIS OF METAL COMPLEX FORMATION The addition of (C2H&NC1 causes a much larger decrease in the rate of the catalysed reaction than NaCl. (C2H&NC1 also has a much larger effect on the sur- face potential, (table 3), which implies that desorption of the nickel ion is the major factor influencing the rate. 150 7 100 z?. -I I 50 0 \1 ' P 0'8, -.- - '. 1 I I I 0.02 0.04 0.06 0.08 [added salt]/rnol dm-3 FIG.5.-Effect of salt concentration on T-l. [Niz+] = loe3 moI dm-3, [SLS] = 0.025 mol dm-3, T = 298.2 K. ( l a ) Added NaCl; (16) addded NaCl corrected for NiZ+ dilution on the surface arising from a decrease in cmc. (2) Added (C2H5)4NC1 ; (26) added (CZH5)+NCI, corrected for the decrease in c.m.c. The lack of catalysis shown by sodium methylsulphate confirms that alkyl sulphates have no catalytic abilityper se, but that micelles are necessary. The failure of poly- vinylsulphate and Triton X-100 to catalyse the reaction shows that a linear charged surface or a hydrophobic environment are not alone able to concentrate the Ni2+ and PADA reactants. The small decrease in rate caused by addition of these reagents probably reflects a partitioning of one reagent (Ni2+ in the case of polyvinylsulphate, and PADA with Triton X-100) but not the other, out of the bulk solvent.When two ionic species are used as reactants, as in the case of the reaction between Co(NH&C12+ and Hg2+ in the presence of anionic micelles and polyvinylsulphonate,22 large catalytic effects have been observed in both cases. We are indebted to Mr. K. J. A. Hargreaves, who carried out preliminary measure- ments on this system. We thank the S.R.C. for a fellowship (to A. D. J.) and grants for equipment associated with this work. We acknowledge also valuable discussions with Dr. W. Knoche and his colleagues (by a NATO Travel Grant), Dr. J. Holzwarth and Dr. W. J. Albery. E. H. Cordes, Reaction IGnetics in Micelles (Plenum Press, New York, 1973). J. H. and E. J. Fendler, Catalysis in Micellar and Macromolecular Systems (Academic Press, New York, 1975). R. G. Wilkins, Inorg. Cheni., 1964, 3, 520. M. A. Cobb and D. N. Hague, J.C.S. Faruhy I, 1972, 68,932.A. D. JAMES AND B. H. ROBINSON 21 E. F. Caldin and P. Godfrey, J.C.S. Faraday I, 1974, 70, 2260. H. P. Bemetto and Z. Sabet Imani, J.C.S. Faraday I, 1975,71, 1143. Series, No. 49, (Amer. Chem. SOC., Washington, D.C., 1965), p. 55. K. Letts and R. A. MacKay, Inorg. Chem., 1975,14,2990. ’ M. Eigen and R. G. Wilkins, Mechanisms of Inorganic Reactions, ed. R. F. Gould, Adv. Chem. * M. B. Lowe and L. N. Phillips, Nature, 1961,190,202. lo B. H. Robinson, N. C. White and C. Mateo, Adv. Molecular Relaxation Processes, 1975,7,321. l1 M. Eigen and L. DeMaeyer, Technique of Organic Chemistry, ed. S . L. Friess, E. S. Lewis and l2 G. S. Hartley and J. W. Roe, Trans. Faraday SOC., 1940,36, 107. l3 A. D. James, B. H. Robinson and W. Knoche, to be published. l4 D. Stigter, J. Colloid Interface Sci., 1967, 23, 379. P. Mukerjee and K. Banerjee, J. Phys. Chem., 1964, 68,3567. l6 P. Mukerjee and K. J. Mysels, Critical Micelle Concentrations of Aqueous Surfactant Systems (National Bureau of Standards, Washington, 1971). J. Oakes, J.C.S. Faradhy 11, 1973, 69, 1321. A. Weissberger (Interscience, New York, 1963), vol. 8, part 2, p. 913. l8 G. S. Hartley and C. S. Samis, Trans. Faraday Soc., 1938,34, 1288. l9 H. P. Bennetto and E. F. Caldin, J. Chem. SOC. A,, 1971, 2200. 2o D. Stigter, J. Colloid Interface Sci., 1974, 47,473. 21 F. Reiss-Husson and V. Luzzati, J. Phys. Chern., 1964,68, 3504. 22 J.-R. Cho and H. Morawetz, J. Amer. Chem. SOC., 1972, 94, 375. (PAPER 6/2303)

ISSN:0300-9599    

DOI:10.1039/F19787400010

出版商:RSC    

年代:1978

数据来源: RSC

摘要:

Thermodynamics of Hydrobromic Acid in Dioxan+ Water Mixtures from Electromotive Force Measurements at Different Temperatures BY BIJOY K. DAS AND PRA~ANNA K. DAS* Chemistry Department, Ravenshaw College, Cuttack-753003, India Received 31st December, 1976 Electromotive force measurements of the cell Pt, Hz/HBr(m), dioxan(X) HzO( Y)/A@r/Ag have been made at 15, 25, 35 and 45°C for solvent compositions X = 10, 20, 30, 40, 60 %(w/w) of dioxan. These have been used to evaluate the standard potentials of the cell, the mean activity coefficient of HBr (molal scale) and the thermodynamic functions (mole-fraction scale) for the transfer of HBr from water to the respective dioxan+water media. The AG; (free energy of transfer of the acid from water to various solvents) values along with those for hydrochloric acid, are briefly discussed in relation to ion solvation. E.m.f.measurements of cells without liquid junction potentials have shed con- siderable light on the thermodynamic behaviour of hydrochloric acid in various aquo-organic solvents and in a few non-aqueous solvents. Very little is known about the effect of the changes in solvent composition on the thermodynamic behaviour of other halogen acids. The effect on such properties of hydrobromic acid in 10, 20, 30, 40 and 60 %(w/w) dioxan + water mixtures at 15, 25, 35 and 45°C are reported in this paper from the e.m.f. measurements of cell (I) : Pt, H,(g)/HBr(m) dioxan(X), H20( Y)/AgBr/Ag. (1) The standard potential of Ag-AgBr electrode has been determined by Feakins and Turner at 25°C in 20 and 45 %(w/w) dioxan +water mixtures using Owen’s borate- buffered cell, and by Mussini et aL2 in 5, 10, 15, 20, 45, 70 and 82 %(w/w) dioxan+ water mixtures in the temperature range 20-35°C using cell (I).The values of the standard potential of the Ag-AgBr electrode at 25°C in 20 and 45 %(w/w) mixtures reported by the former workers are 0.059 91 and 0.031 83 V and by the latter group are 0.060 15 and 0.034 47 V, respectively. This prompted us to reinvestigate cell (I). The solvent systems chosen were of 10, 20, 30, 40 and 60 %(w/w) dioxan+water mixtures, to correspond with our previous investigation on the Ag-AgC1 electrode using the same solvent compositions. EXPERIMENTAL Dioxan was of B.D.H. AnalaR quality and was purified as described earlier.4 E. Merck G.R.hydrobromic acid was diluted with triply distilled water to the approximate composition of the constant boiling mixture and was distilled. The middle fraction of the constant boiling mixture was collected. The bromide content was analysed gravimetrically and this was used as a stock solution. Experimental solutions of the desired concentrations were prepared by diluting known amounts of solution with known amounts of solvent. During handling of the solutions, exposure to air was avoided as far as practicable. The acid concentrations of the solutions were occasionally checked after the experiments. No significant change was detected. 22B. K. DAS AND P. K. DAS 23 The Ag-AgBr electrodes were of the thermal type described by Ives and Janz and these electrodes, in the solvent mixtures studied, were found to be stable for more than a month.Electrodes having a bias potential within +O.O5mV were used. The other experimental procedures were similar to those adopted with the Ag-AgC1 electrode described previ~usly.~ The cell potentials were measured with an accuracy of kO.05 mV by a Leeds Northrup K-2 potentiometer in conjugation with a matching galvanometer. The potentiometer was standardised against a certified Weston standard cell maintained at constant temperature. The cells attained equilibrium after 4 h in all the solvent mixtures studied at all temperatures except at 45"C, where equilibrium was reached in 33 h. TABLE 1 .-PARAMETERS NECESSARY FOR THE EVALUATION OF E'' OF EQN (3) IN D1OXAN-k WATER MIXTURES AT DIFFERENT TEhfPERATURES I0 % dioxan (Go = 19.57) 15°C 25°C 35°C DS 73.21 69.68 66.18 P s l m Hg 14.70 27.60 48.60 Almol-3 kg* 0.596 0.609 0.627 polkg m-3 1.0119 1.0058 1 .W17 l3lm-l mol-* kg* 0.3463 0.3489 0.3522 30 % dioxan (Go = 23.66) Dl 54.75 51.89 49.1 8 P s l m Hg 19.30 35.20 62.20 polkg m-3 1.0294 1.0217 1.0159 Almol-3 kg* 0.921 0.961 0.978 lo-'' l3lm-l mol-* kg* 0.4004 0.4062 0.4085 40 % dioxan (Go = 26.42) DS 45.42 42.97 40.65 P s l m Hg 21.90 38.80 68.40 polkg m-3 1.0362 1.0289 1.0217 A/mol-3 kg* 1.219 1.252 1.302 10-lo l3lm-l mol-3 kg* 0.4396 0.4436 0.4493 60 % dioxan (Go = 34.47) 0 s 27.37 25.85 24.41 P s l m Hg 25.80 44.20 77.60 polkg m-3 1.0441 1.03 62 1.0285 B/m-l mol-3.kgt 0.5663 0.5733 0.5799 Almol-3 kg3 2.605 2.695 2.799 45°C 63.11 82.00 0.9994 0.641 0.3549 46.62 102.20 1.0119 1.010 0.4130 38.46 118.80 1.0168 1.348 0.4546 23.05 124.20 1.0218 2.907 0.5874 Duplicate experiments were performed simultaneously in each case and the duplicates generally agreed within 40.5 mV.Vapour pressures of the solvent mixtures were obtained from the data of Hovorka, Schaefer and Dreisbach,6 interpolating or extrapolating where necessary. The e.m.f. readings were corrected to one atmosphere pressure using these vapour pressure data. The densities of the solvent mixtures were determined pyknometric- ally and the dielectric constants of the solvents were calculated using the equation proposed by Akerlof and Short.' The densities (po), dielectric constant (Ds), vapour pressure (ps) and the Debye-Huckel parameters (molar) for the solvent mixtures studied are reported in table 1.The Debye-Huckel parameters were calculated theoretically. For a 20 % dioxan+ water mixture the values of parameters were taken from Harned's work.*24 THERMODYNAMICS OF HBr IN DIOXAN + WATER TABLE 2.-E.M.F. OF CELL (I) (E/v) CORRECTED TO 1 atm. PRESSURE IN VARIOUS DIOXANf WATER MD(TURES AT DIFFERENT TEMPERATURES 1000 mHBr 2.99 3.94 4.99 6.00 7.01 7.98 8.97 10.01 19.61 29.77 40.77 49.92 60.09 69.87 79.62 90.00 100.41 2.89 3.79 4.99 6.04 6.94 8.01 9.06 10.20 19.91 29.86 40.15 50.01 59.97 69.89 80.19 90.27 99.92 3.30 3.94 4.92 5.95 7.03 8.13 9.01 9.91 20.22 29.10 40.09 15OC 25°C 35°C 10 % dioxan 0.3617 0.3479 0.3373 0.3286 0.3213 0.3149 0.3094 0.3044 0.271 8 0.2531 0.2396 0.2293 0.2209 0.2137 0.2075 0.2021 0.1971 0.3575 0.3438 0.3332 0.3246 0.3173 0.31 10 0.3055 0.3006 0.2685 0.2499 0.2368 0.2266 0.21 84 0.21 14 0.2053 0.2000 0.1953 0.3508 0.3373 0.3268 0.3183 0.3111 0.3050 0.2995 0.2947 0.2630 0.2447 0.23 17 0.3675 0.3533 0.3422 0.3333 0.3257 0.3191 0.3134 0.3082 0.2746 0.2550 0.2412 0.2309 0.2219 0.2144 0.2080 0.2023 0.1969 20 % dioxaii 0.3630 0.3489 0.3380 0.3290 0.3215 0.3151 0.3093 0.3044 0.271 1 0.2519 0.2382 0.2278 0.21 92 0.2120 0.2058 0.2002 0.1953 30 % d' ioxan 0.3539 0.3399 0.3291 0.3204 0.3130 0.3066 0.3010 0.2960 0.2634 0.2445 0.23 1 1 0.3708 0.3561 0.3447 0.3354 0.3276 0.3209 0.3149 0.3095 0.2750 0.2549 0.2406 0.2295 0.2205 0.2129 0.2062 0.2004 0.1950 0.3666 0.3520 0.3407 0.3315 0.3238 0.3171 0.3 112 0.3060 0.271 8 0.2520 0.2379 0.2271 0.21 83 0.2108 0.2044 0.1987 0.1936 0.3574 0.3429 0.3318 0.3227 0.3 151 0.3085 0.3027 0.2976 0.2640 0.2446 0.2308 450c 0.3737 0.3585 0.3468 0.3372 0.3292 0.3222 0.31 60 0.3106 0.2748 0.2540 0.2394 0.2280 0.21 87 0.2109 0.2041 0.1981 0.1927 0.3681 0.3530 0.3413 0.3319 0.3239 0.3170 0.31 10 0.3055 0.2703 0.2500 0.2355 0.2243 0.2152 0.2075 0.2008 0.1949 0.1896 0.3583 0.3435 0.3320 0.3227 0.3148 0.3080 0.3020 0.2968 0.2622 0.2423 0.2281B .K . DAS AND P. K . DAS 25 1000 mEiBr 50.02 59.02 70.06 80.12 89.92 100.12 3.07 3.99 5.01 5.97 6.99 8.10 9.00 9.98 19.92 29.51 40.01 50.10 59.89 70.01 76.27 88.98 101.01 2.96 4.02 4.95 6.06 7.0 1 7.93 9.00 9.98 20.04 28.99 40.30 49.19 58.96 70.03 79.82 90.30 100.23 15°C 25°C 35OC 30 % dioxan (contd.) 0.2217 0.2207 0.2202 0.2136 0.2123 0.2117 0.2067 0.2052 0.2043 0.2008 0.1990 0.1980 0.1956 0.1931 0.1924 0.1908 0.1881 0.1874 0.3441 0.3308 0.3205 0.3122 0.3051 0.2991 0.2937 0.2890 0.2581 0.2402 0.2276 0.2179 0.2099 0.2032 0.1973 0.1922 0.1875 0.3047 0.2922 0.2828 0.2750 0.2686 0.2630 0.2582 0.2538 0.2259 0.2099 0.1985 0.1896 0.1824 0.1762 0.1709 0.1662 0.1628 40 % dioxan 0.3445 0.3307 0.3201 0.3115 0.3043 0.2980 0.2925 0.2876 0.2559 0.2375 0.2245 0.2145 0.2062 0.1995 0.1995 0.1883 0.1836 60 % dioxan 0.3047 0.2919 0.2822 0.2743 0.2676 0.2619 0.2569 0.2525 0.2237 0.2071 0.1951 0.1854 0.1775 0.1708 0.1639 0.1 578 0.1526 0.3447 0.3305 0.3196 0.3107 0.3032 0.2968 0.2912 0.2861 0.2534 0.2345 0.2212 0.2209 0.2025 0.1954 0.1893 0.1838 0.1789 0.3021 0.2890 0.2790 0.2708 0.2638 0.2583 0.2532 0.2485 0.2193 0.2018 0.1888 0.1790 0.1707 0.1633 0.1568 0.1511 0.1460 450c 0.2173 0.2083 0.2008 0.1943 0.1885 0.1834 0.3446 0.3300 0.31 87 0.3096 0.3019 0.2953 0.2895 0.2844 0.2508 0.23 13 0.2175 0.2069 0.1980 0.1906 0.1842 0.1782 0.1740 0.2973 0.2841 0.2738 0.2656 0.2588 0.2530 0.2478 0.2432 0.2135 0.1953 0.1826 0.1709 0.1632 0.1557 0.1489 0.1418 0.1371 RESULTS AND DISCUSSION The e.m.f.(E) values of cell (I) after correction to 1 atm pressure in the usual way are reported in table 2. The e.m.f. expression of cell (I) is given by : where E: is the standard molal potential of the cell, A* is the mean molal activity E = Eg-2 k log (in&) (1)26 THERMODYNAMICS OF HBr I N DIOXAN + WATER coefficient of HBr at the molality m and k equals 2.3026 RTJF. The mean activity coefficient A* is given by eqn (2)9 AC4 1 +BaoC4 -logA* = +pm +log (1 f0.002 Gorn).In this equation A and B are the Debye-Huckel constants on the molar scale, a, is the ion-size parameter, j? is an adjustable parameter and Go is the average molecular weight of the solvent. Substituting eqn (2) in eqn (I) and rearranging, we obtain, E'' = ~ + 2 k l o g m- 2kAc3 -2k log (1 +0.002 G0m) = Ei-2kprn. 1 + Baoc* (3) From eqn (3) it is expected that Eo' should be a linear function of m when a suitable value of ion-size parameter is chosen. The a. values for different solvent mixtures TABLE 3.-ION-SIzE PARAMETER (IN A) wt. %dioxan 15°C 25°C 35°C 45°C 10 5.0 5.0 5.0 5.0 20 5.2 5.2 5.2 5.0 30 5.2 5.3 5.2 5.0 40 5.3 5.2 5.2 5.0 60 5.8 5.7 5.5 4.8 at different temperatures are chosen in such a way that the deviation from linearity of the plot between EO' and m is minimum. A deviation of k0.2 mV in E; was seen when the a.value was varied within k0.3 A of the chosen value. The values of a, TABLE 4.-sTANDARD MOLAL POTENTIALS (EiIV) OF THE Ag-AgBr ELECTRODE IN DIOXANf WATER MIXTURES AT VARIOUS TEMPERATURES wt % dioxan 15°C 25°C 3 5°C 45°C 10 0.0698 0.0654 0.0584 0.05 1 1 20 0.0648 0.0601 0.0534 0.0445 30 0.0570 0.0497 0.0429 0.0334 40 0.0486 0.0385 0.0282 0.0174 60 0.0013 - 0.0097 - 0.0236 - 0.0405 TABLE 5 . V A L U E S OF THE CONSTANTS a, b AND C [See q n (411. wt. % dioxan alv 1 0 4 bIv(cq-1 106 c~v("c)-~ 10 0.0651 5.56 7.33 20 0.0601 5.61 10.63 30 0.0502 7.23 5.55 40 0.0385 10.20 1.68 60 - 0.0097 12.48 14.60 and E; are recorded in tables 3 and 4, respectively. The average standard deviation in A': is k0.l mV for 10, 20 and 30 % dioxan+water mixtures and k0.2 mV for 40 and 60 % dioxan+water mixtures.The E; values for each solvent composition were fitted by the method of least squares to eqn (4) Eg = a-b(t-25)-~(t-25)~ (4)B . K. DAS AND P. K . DAS 27 where t is the temperature in "C. The constants a, b and c are listed in table 5 . The Eg value at 25°C in 20 % dioxan determined by us is intermediate between the value of Feakins and Turner and Mussini et aL2 TABLE 6.-MEAN MOLAL ACTIVITY COEFFICIENT OF HBr IN VARIOUS DIOXAN+ WATER MIXTURES AT 25°C wt. % dioxan m 10 20 30 40 60 0.003 0.005 0.008 0.010 0.020 0.050 0.080 0.100 0.93 1 0.914 0.896 0.886 0.853 0.799 0.779 0.773 0.917 0.896 0.875 0.862 0.823 0.765 0.734 0.720 0.895 0.870 0.843 0.830 0.782 0.717 0.684 0.676 0.865 0.834 0.801 0.784 0.727 0.650 0.544 0.534 0.733 0.683 0.632 0.608 0.532 0.449 0.426 0.425 The stoichiometric mean activity coefficient A* of HBr in various solvent media was calculated with the help of eqn (1).The values of A* were plotted against m on a large scale and from the plots the activity coefficients at rounded molalities were read off and these values at 25°C are given in table 6. An error of k0.05 mV in the e.m.f. values corresponds to an error of -1-0.002 in the value of A* at 25°C. The values of activity coefficient at a particular molality decrease with increasing dioxan content in the medium, as expected from Debye-Hiickel theory. The standard thermodynamic quantities (AG,", AS," and AH,") for the transfer process : HBr (in water) + HBr (in various dioxan + water media) can be calculated from the standard e.m.f.of the cell in water and in respective dioxan+water media on the mole-fraction scale using Feakin's method.1° These are tabulated in table 7. The probable uncertainties in AG; are +, 16 J mol-l, in AH," are k21 J mol-l, and in AS; are k0.5 J K-l mol-' in 10,20 % solvent composition and -1- 1.0 J K-' mol-l in 30, 40, 60 % solvent composition. The standard Gibbs free energies of transfer, AG; are observed to be positive for all the solvent compositions and increase with increasing temperature. The positive AG; values indicate that HBr is in a higher free energy state in dioxan +water mixtures than in water, suggesting that water has more affinity for HBr (or the proton) than for dioxan+water mixtures.Similar conclusions were also drawn for HC1 in dioxan+water mixtures.ll The values of AS: and AH," are negative for all the solvent mixtures, so the enthalpy in dioxan+ water mixture is less than in pure water and hence the net amount of order created by HBr in dioxan+water mixtures is more than in pure water. Since single-ion values of free energy are not available presently for the solvent mixture studied, the method adopted by Khoo and Chan l2 was followed to study the ion-solvent interaction. In this method, consider a function AG;' on the mole fraction scale given by eqn (5) The difference between the free energies of transfer of hydrochloric and hydrobromic acids gives the difference between the freeenergies of transfer of the chloride and bromide ions AG,"(cl- ~ and AGt(Br-) respectively.The AG:(HcI) values required here were calculated from Harned's data l3 for 20 % dioxan and for 10, 30, 40 and28 THERMODYNAMICS OF HBr IN DIOXAN 4- WATER 60 % dioxan from data reported el~ewhere.~ The values of AG,"' at 25°C are given below : wt. Xdioxan 10 20 30 40 60 AGP'/Jmol-l 235 757 1149 1948 2473. AG,"' for all the solvent compositions is positive and increases with increasing concentration of dioxan in the mixed solvents. This is qualitatively in agreement with the Born theory which predicts that the bromide ion should be in a lower free TABLE 7.-FREE-ENERGY, ENTHALPY AND ENTROPY OF TRANSFER OF HBr FROM WATER TO D1OXAN-k WATER MIXTURES AT DIFFERENT TEMPERATURES T/"C 15 25 35 45 15 25 35 45 15 25 35 45 15 25 35 45 15 25 35 45 AG; /J mol-1 AHo/J mol-1 10 % dioxan 200 - 351 165 - 467 306 - 370 41 5 - 305 20 % dioxan 252 - 514 230 - 650 328 - 612 577 - 424 30 % dioxan 520 - 992 734 - 1002 835 - 1021 1124 - 853 40 % dioxan 808 - 2343 1271 - 2349 1687 -2180 2076 - 2045 60 % dioxan 4093 - 2006 4603 - 2405 5324 - 2161 6260 - 1718 ASo/J K-1 mol-1 - 1.98 -2.12 -2.19 - 2.26 - 2.75 - 2.95 - 3.05 -3.15 - 5.44 - 5.83 - 6.02 - 6.22 -11.33 - 12.14 - 12.55 - 12.95 - 21.93 - 23.50 - 24.29 - 25.08 energy state than the chloride ion in mixed solvents of lower dielectric constant than water.Therefore, the Born equation may be expected to fit increasingly better as the dioxan content of the mixture is increased. The same observations were made by Feakins and Turner.l It may be possible to split the AG," values into two parts, as Roy, Vernon and Bothwell l4 have done, a " non-electrostatic " or " chemical " contribution, denoted in their terminology by AG&, and an " electrostatic " contribu- tion AGE, which has been calculated from the Born equation [eqn (6)].AG,",, = (Ne2/2) (jS - - ;J($+;) -B . K . DAS AND P. K. DAS 29 where the radius of hydrogen ion (r+) may be taken as 2.76AI5 and that of the bromide ion (r-) as 1.95A;16 0, and Dw are the dielectric constants of the mixed solvent and water respectively. To calculate the electrostatic part of the entropy of transfer : eqn (6), after differentiation and algebraic manipulation, yields where the values of d In DJdTand d In D,/dTcan be evaluated from simple empirical eqn (8) :17 d In D/dT = - l/O (8) in which 8 is a constant, characteristic of medium. So eqn (7) may be written as : From the slopes of the linear plots of log D against T for the respective dioxan + water mixtures, the following values of 0 were calculated: wt.% dioxan 0 10 20 30 40 60 0 220 202 194 187 181 175. From a knowledge of AG,", and AS;,, the electrostatic part of the enthalpy change AH& has been computed. The chemical contribution of the free energy of transfer (AG,",), entropy of transfer (ASCh) and enthalpy of transfer (AH&,) can then be obtained by subtracting the respective electrostatic contribution values from the molar quantities. These values so calculated at 25°C are presented in table 8.It is TABLE 8.-ELECTRICAL AND CHEMICAL PART OF THE THERMODYNAMIC QUANTITIES ACCOMPANY- ING THE TRANSFER OF HBr FROM WATER TO DIOXAN+ WATER MIXTURES AT 25'C Wt % 10 502 -337 -709 242 -4.06 1.94 20 1152 -922 -1332 682 -8.33 5.38 30 2025 -1290 -2149 1147 -14.00 8.17 40 3263 -1992 -3272 923 -21.92 9.78 60 8035 -3432 -7031 4626 -50.53 27.03 dioxan AG& A c t h q, AH& AS& AS&# evident from an examination of this table that the chemical contribution of the free energy of transfer AGC, is negative and appears to be a solvent parameter which measures the increase in basicity in the dioxan + water mixture. Thus, considering only the chemical contribution of the free energy AGE, which has negative values, the dioxan + water mixture appears to be more basic than water, but the electrostatic factors predominate over the chemical contribution or the solvation, resulting in an overall unfavourable effect on the transfer process from water to dioxan + water mixtures ; hence dioxan + water mixture is more acidic than water.The electrostatic part of the enthalpy and entropy have negative values, whereas the chemical contri- bution of the enthalpy and entropy is positive. The authors thank the Council of Scientific and Industrial Research, New Delhi, India for award of a research fellowship to one of them (B. K. D.).30 THERMODYNAMICS OF HBr I N DIOXAN + WATER D. Feakins and D. J. Turner, J. Chem. SOC., 1965,4986. T. Mussini, C. M. Formaro and P. Andrigo, J. Electroanalyt. Chem., 1971, 33, 177. P. K. Das and U. C. Misra, Electrochim. Acta, 1977, 22, 59. S. C. Mohanty, U. C. Misra, K. C. Singh and P. K. Das, J. Indian Chem. SOC., 1973,50, 302. D. J. G. Ives and G. J. Jam, Reference Electrodes-Theory and Practice (Academic Press, New York, 1969), p. 208. F. Hovorka, R. A. Schaefer and D. Dreisbach, J. Amer. Chem. SOC., 1936, 58,2264. ' G. Akerlof and 0. A. Short, J. Amer. Chem. SOC., 1936,58, 1241. * H. S. Harned and J. G. Donelson, J. Amer. Chem. SOC., 1938,60, 339. E. Huckel, Phys. Z., 1925,26,93. lo D. Feakins and P. Watson, J. Chem. SOC., 1963,4734. l1 B. K. Das, U. C. Misra and P. K. Das, J. Indian Chem. SOC., communicated. l2 K. H. Khoo and C. Y . Chan, Austral. J. Chem., 1975, 28,721. l3 H. S. Harned, J. Amer. Chem. SOC., 1938, 60, 334. l4 R. N. Roy, W. Vernon and A. L. M. Bothwell, Electrochim. Acta, 1972, 17, 5 . l5 M. Paabo, R. G. Bates and R. A. Robinson, J. Phys. Chem., 1966,70,247. l6 L. Pauling, The Nature of the Chemical Bond (Cornell Univ. Press, Ithica, New York, 3rd edn, l7 R. W. Gurney, Ionic Processes in Solution (McGraw Hill, New York, 1953), p. 16. 1960), p. 521. (PAPER 6 123 64)

ISSN:0300-9599    

DOI:10.1039/F19787400022

出版商:RSC    

年代:1978

数据来源: RSC

摘要:

Effect of Oxygen Chemisorption and Photodesorption on the Conductivity of ZnO Powder Layers BY NICO M. BEEKMANS~ Mullard Research Laboratories, Redhill, Surrey Received 25th January, 1977 Chemisorption of oxygen on the surface of the grains of ZnO powder layers mainly controls the photoconductivity. The adsorption of oxygen ions is regarded as a chemical reaction at the interface and involves oxygen from the gas atmosphere and electrons from the metal oxide. The changes in the conductivity of ZnO-layers calculated on this basis are in fair agreement with the experimental results. At low light levels deviations from the theory are observed which result from an “ overdepletion ’’ of the conductivity controlling regions in the powder layer. Considering a ZnO layer as a secondary photoconductor has allowed the calculation of a maximum photosensitivity for such layers.1. INTRODUCTION The electrical conductivity in layers of fine grains of n-type ZnO can be reduced considerably by chemisorption of negatively charged oxygen ions on the surface of \ -- -- I ‘-H FIG. l.-(cz) Cross-section of a powder layer ; shading indicates surface space charge region. (6) Cross-section of a connecting “ neck ” in a powder layer and energy band diagrams corresponding to three cuts across the neck (after Hutson).+ t Presentraddress : Philips Research Laboratories, Eindhoven, The Netherlands. 3132 CONDUCTIVITY OF ZnO the grains. Subsequent illumination with light of suitable wavelength desorbs the oxygen from the surface and restores the conductivity. Effectively such powder layers behave as very sensitive photoconductors, much more sensitive than can be expected from the increase in the bulk free carrier concentration under illumina- ti0n.l.The electronic charge involved in the chemisorption is extracted from the semiconductor. As a result a positively charged depletion layer is formed under the surface to compensate for the negative surface ~ h a r g e . ~ - ~ The effects of depletion regions on the conductivity are illustrated in fig. 1. Attractive forces between the grains, such as Van der Waals forces, cause the formation of contact regions or necks between the grains. For the ZnQ powder used the diameter of these necks can be estimated as - 10 % of the grain diameter.6 By correct matching of grain size, carrier concentration and oxygen pressure, the depletion layers may become thick enough to completely deplete the smallest regions in the powder layer, i.e.the necks between the grains. It is the purpose of this paper to show that the concept of chemisorption on the surface applied to a model of depletion of the necks linking the grains of a powder layer allows the detailed behaviour to be calculated. Section 2 develops the model for the conductivity of a single grain-to-grain contact as a function of geometry, illumination and oxygen pressure. Some experimental results illustrate the feasibility of the model. The effects of percolation is powder layers introduced in section 3 explain the satisfactory agreement between the behaviour of the model for uniform particle sizes and the experimental layers.Using photoconduction theory in section 4 the maximum photosensitivity of ZnO powder layers is calculated. 2. THEORY FOR UNIFORM PARTICLE SIZES In this section a model will be developed for the effects of chemisorption on the conductivity in the neck between two grains of a metal oxide semiconductor. We assume that in oxygen or in air at atmospheric pressure oxygen alone will be adsorbed on the surface of a neck. On the surface a limited number of sites (n, cm-2) are available for adsorption of oxygen. A certain fraction of the oxygen adsorbed may have trapped a free electron from the ZnO. The chemisorption reaction on these sites can be descripted by the scheme :* O,+e; e 0;. (2.2) Positions in the gasphase, at the surface and in the bulk of the semiconductor are indicated by the subscript g, y and s, respectively.Illumination of the semi- conductor with light of suitable wavelength creates electron-hole pairs. Holes generated in the space charge region are attracted to the surface and may discharge an oxygen ion there : (kv} + e; + h$, h$ +OF 3 0,. In this scheme (kv) stands for an absorbed photon with energy hv. We introduce the relative surface occupation r as the fraction of the total surface site concentration (n,) occupied by oxygen ions. As will be shown later the interaction between the gas atmosphere and the ZnO surface is faster than the chemisorption and desorption reactions. Also the creation of an electron-hole pair after absorption * The Kroger and Vink notation will be adopted, see F.A. Kroger, 312e Chemistry of Imperfect CrystaZs (North HollandlAmerican Elsevier 2nd edn, 1974), vol. 2, p. 1.N. M . BEEKMANS 33 of a photon is assumed to be a fast process. Under those conditions the reactions (2.2) and (2.4) are rate determining. Variations of r with time will result from the balance between the adsorption reaction (2.2) and the opposing parallel desorption reactions (2.2) and (2.4), according to : d r - = k'rony-k21'-khy. dt In this rate equation k', k" and k2 are constants, ny and h, stand for respectively the electron and the hole concentration at the surface and To is the concentration of the adsorbed oxygen atoms at the surface. Irradiation of the surface with I W of light consisting of quanta of energy hv creates a number of electron-hole pairs per unit time.The concentration of holes near the surface resulting from this flux is propor- tional to the number of holes generated per unit time : 61 hy cc -- hv (2.5 j where 6 is a conversion efficiency factor which depends on the spatial coordinates in the layer and on the wavelength. An equilibrium between gas atmosphere and the surface according to reaction (2.1) implies : ro cc P&. The negative surface charge caused by the chemisorbed oxygen is compensated by a positive space charge region in the semiconductor. The electron concentration at the surface ny is related to n and to the difference in electrostatic potential # between bulk and surface : where k is the Boltzmann constant and T the absolute temperature.Substitution of the eqn (2.6) to (2.8) in eqn (2.5) and introduction of the constants kl and k3 gives : n, = n exp (-q#lkT), (2.8) - = k1P&nexp(-q4/kT)-T d r dt Integration of Poisson's equation over the thickness L of the space charge region gives the well known relation between L and the surface potential # :' (2.10) where E is the relative dielectric constant and go the permittivity of vacuum. The surface charge per unit area must be equal to the space charge under the same area. This condition gives directly a relation between the relative surface occupation and the surface potential : (2.11) where n, is the number of sites at the surface available for oxygen adsorption. Substitution of eqn (2.11) in eqn (2.9) eliminates the surface potential as a parameter in the latter: (2.12) 1-234 CONDUCTIVITY OF ZnO The reaction equations in this section assume the chemisorption of oxygen as single charged ions.However, the actual ionisation state of the chemisorbed oxygen is still uncertain. 0; ions as well as 0- ions can exist while transitions between the two states are possible.8* For reasons of simplicity the 0- state has arbitrarily been chosen. 2.1 CONDUCTIVITY I N A NECK BETWEEN TWO GRAINS The initial concentration of the free charge carriers in a neck region with a constant cross-section in the direction of the current is n ~ r n - ~ . Suppose that oxygen at the surface of the neck traps some electrons reducing the average concentration in the neck region to n* ~ r n - ~ . The ratio between the volume of the neck region and its surface area will be defined asfcm.Assuming the number of sites at the surface available for oxygen adsorption to be n, cm-2, then the relative surface occupation r is: n-n* nt r=-$ Conversion of carrier concentration into conductivity gives : r = (1-5): (2.13) (2.14) where cr stands for the average conductivity in the partially depleted neck and om for the conductivity in the undepleted neck. The derivation of eqn (2.14) did not require the definition of discrete depletion layers and has as such the advantage that the actual shape of the depletion layers is not important. When applied to a partially depleted neck with limited depletion layers near the surface, om stands for the conductivity of the undepleted channel in the centre of the neck.2.2 RELATIONS BETWEEN PARAMETERS Relations exist between several of the parameters contained in eqn (2.12) which reduce effectively the number of independent variables. Under conditions of equilibrium in darkness (dT/dt = 0 and I = 0), eqn (2.12) yields a relation between kly k2 and r : Y (2.15) where rd stands for the relative surface occupation of the stationary state in darkness, The conductivity of the neck drops to zero when it is just completely depleted. At this moment eqn (2.14) becomes : ?l ra = -f. (2.16) nt Another useful relation can be derived by solving eqn (2.12) for very low values of I' and substitution of eqn (2.14) : 0 = om[ 1--P 7 h2 k 1 1 t f o r a - a,. (2.17) Suppose the rate of adsorption is not slowed down by increasing desorption effectsN.M. BEEKMANS 35 and an opposing surface potential. The conductivity in the neck would then be reduced to zero in a characteristic time (7). For CT = 0, eqn (2.17) becomes : 7 = -* f PO3 (2.18) ntk1 Eqn (2.15), (2.16) and (2.18) enable the calculation of internally consistent sets of values for k l , kZ, r,, z andf. In principle the number of sets of values that satisfy the conditions of the equations mentioned is unlimited. In practice, however, parameters which can be derived from experiments such as the neck ratio (f), characteristic time (2) and rise time of the photoconductivity curve reduce very strongly the range of values for the rate constants and for the surface occupation in darkness. The values used for the material constants in the calculation of the photoconductivity are collected in table 1 .The absolute accuracy of most of the values in the table is not very high. Some parameters can be chosen freely within a certain range. However, the conditions of internal consistency demands then some accuracy for the other parameters. TABLE PA PARAMETERS USED FOR THE CALCULATION OF THE NECK CONDUCTMTY relative surface occupation adsorption rate constant kl desorption rate constant kz photodesorption rate constant k3 characteristic time z ratio between neck volume f density of surface sites nt dielectric constant & temperature T donor concentration n in darkness r d and surface area 4.647~ 10-4 9 . o ~ 10-4 s-1 kzhvlS cm2 1.463 x cm3 bar-* s-l 0.032 s 5 . 6 2 ~ 1W6 cm 1.21 x 1015 cm-2 10 300 K lo1' CM-~ No direct estimation for k3 and 6 has been made.The value of the conversion factor 6 depends on many factors such as geometry, surface condition and position in the layer. The photo assisted desorption reaction (2.4) is so closely related in nature to the spontaneous desorption reaction (2.2) that it seems reasonable to assume k3 to be proportional to k2. This assumption, together with the acceptance of relative illumination levels instead of absolute ones, provides sufficient basis for an estimation of the effects of illumination on the effective conductivity in a neck region. 2.3 COMPARISON BETWEEN THEORY AND EXPERIMENT The change in conductivity with time in a neck at different light levels has been calculated by integration of eqn (2.12) and applying eqn (2.14) on the basis of parameter values listed in table 1 (see fig.2). The neck is assumed to be illuminated for 3 min starting from t = 2 min. Fig. 3 shows an experimental observation of the conductance change with time under illumination* as found in a thin layer (0.5 x 0.5 x 2 x cm3) of fine-grained ZnO powder. The layer has a very low conductance in darkness and is illuminated with U.V. light of various intensities. After an illumination of x3 min duration the conductance returns slowly to its dark con- ductivity level. The general shapes of the curves in fig. 2 and fig. 3 show a close * Details of layer preparation and measuring conditions will be published separately by J. E. Ralph.36 CONDUCTIVITY OF ZnO loo timelmin FIG. 2.-The conductivity change in a neck region with time as calculated for various relative light levels.Between t = 2 min and t = 5 min the neck is illuminated at the relative light level indicated. kl = 1 . 4 6 ~ cm3 bar-* s-l, k2 = 9.00~ s-l, I' = 4 . 6 ~ resemblance. At first sight this seems remarkable since fig. 2 deals with the theoretical conductivity of a single neck, whereas the experimental curves in fig. 3 have reference to a real layer consisting of many grains and with a large variety of geometries of the necks between the grains. However, calculations show that the actual geometry of the neck determines mainly the dark conductivity and only to a limited extent the speed of response and the conductivity under illumination. This is illustrated in fig. 4. The dark conductivities differ by as much as 3 decades but the rise time of the curves and their equilibrium level under illumination are almost the same.I = 0.001x I, I = 0.00 15 X lo timelmin FIG. 3.-Conductance change with time in an experimental ZnO layer. Between t % 0.5 min and t x 4min the sample has been subjected to an illumination strength as indicated. Sample MPIM4, I,, = lo-' W cm-2. In some applications a ZnO layer is illuminated intermittently. Between the light pulses the conductivity of the layer is reset to a low value by means of, for example, a corona discharge.1° For these applications the change in conductivity during aN. M. BEEKMANS 37 I $ - : ’ . ; : 6 :’ : - : 9 L timelmin FIG. 4.-Conductivity in a neck region as a function of time. Necks that differ in their dark conductivities are illuminated between t = 2 min and t = 5 min.Although the dark conductivities of the necks vary over 3 decades, their conductivities under illumination are very nearly the same. kl = 1.46 x cm3 bar-4 s-l, kZ = 9.00~ s-lY I? = 4 . 6 ~ illumination = 1. illumination FIG. 5.-Rate of the conductivity change in a neck region shortly after exposing a neck with a low dark conductivity to a given illumination level. The photosensitivity is calculated for necks with 0 %, 1 %and 3 % overdepletion. kl = 1.46 x 10-19 cm3 b a d s - l , kl = 9.00 x s--l,f= 5.62 x cm.38 CONDUCTIVITY OF ZnO light pulse of given intensity and duration is a criterion for the photosensitivity. The initial conductivity change under illumination can be derived by differentiation of eqn (2.14) and substitution in eqn (2.12).Assuming om % cr we obtain an expression for the rate of conductivity change as a function of illumination : (2.19) The conductivity change per unit of time varies linearly with illumination. In fig. 5 the curve marked 0 % shows the calculated rate of conductivity change for the parameters indicated. Fig. 6 shows the experimental rate of conductance change as can be derived from fig. 3. At high illumination levels the conductance change per unit of time follows closely the predicted slope but at lower light levels the conductance change drops faster than expected. X"X 10121/x I I I I 1 I 16' lo7 16' -I I 10 illumination/W cm-2 J FIG. 6.-Rate of conductance change with time in an experimental ZnO layer shortly after exposing the layer to a given illumination intensity. The broken line shows the theoretical slope for an array of partially depleted necks.The upper curve shows the calculated upper limit for the photo- sensitivity of such a powder layer. Up to now we have considered the necks between the grains as partially depleted. In such a neck a small channel of undepleted ZnO near the centre of the neck provides a path for the electrical current. The width of this channel can be varied by changing the illumination level. Depletion layers in the necks and in the adjacent grains are of equal thickness. Let us consider now an overdepleted neck, i.e. a neck with a diameter less thanN. M . BEEKMANS 39 twice the thickness of the depletion layers in the grains adjacent to the neck.Such an overdepleted neck is characterized by zero conductivity and thicker depletion layers outside the neck than inside. Under sufficiently strong illumination the thickness of the depletion layers both in the neck and in the adjacent grains diminishes and the overdepletion will disappear. Then the thickness of the depletion layers in the neck and in the grains have become equal. Consequently, by changing the neck depletion by illumination from the overdepleted state to the partially depleted state the depletion layer has been reduced in the same shorter time in the neck than in the adjacent grains. The rate at which the thickness of the depletion layer in the neck changes is related to the rate of conductivity change. Hence, we may expect a reduced rate of conductivity change in the overdepleted state.Therefore the extra drop in conductance at low illumination level in fig. 6 suggests that a substantial fraction of the necks in the ZnO layer were overdepleted. Fig. 5 also shows the rate of conduc- tivity change in necks with a radius respectively 1 % and 3 % smaller than the thickness of the depletion layers at equilibrium in darkness. Although eqn (2.19) has been used for the calculations of these curves, it has been derived under conditions which do not include overdepletion. However, it can be shown that the shape of the curves is consistent with the outcome of a more complicated model in which the depletion layers in grain and neck are treated separately. 2.4 EQUILIBRIUM SITUATION Equilibrium in darkness between an oxygen containing atmosphere and a ZnO surface is described by the reactions (2.1) and (2.2).The thermodynamic equilibrium condition for these equations is :11* l2 $luoze+ve = Yo-y* (2.20) In eqn (2.20) we have to use electrochemical potentials (q) instead of chemical potentials ( p ) because the electrons in the semiconductor and the oxygen ions at the surface are separated in space. Consequently, these elements can have different electrostatic potentials. Substitution of the electrochemical potential by chemical and electrostatic potentials converts eqn (2.20) into : +olg 1 0 + 3RT In Po, + pz + RT In n - F+s = p&,+RTln rd-F$y, (2.21) where pz, yo: and ,&- are the standard chemical potentials of the electrons, oxygen and oxygen ions, respectively.These are constants. Further & and 4s stand for the electrostatic potentials at the surface and in the semiconductor, respectively. R is the gas constant and P is Faraday’s constant. Eqn (2.21) is only valid if the relative surface occupation (I?) is less than unity. This condition is fulfilled since we arrived previously at a value for r d of 4.6 x (see table 1). After substitution of +s-4,, = 4, change of constants and some rearrangement eqn (2.21) becomes : ra = KP& n exp [ -q$/kT], (2.22) where K stands for a collection of constants. Comparison of eqn (2.22) with eqn (2.9) applied to the stationary state in darkness (drldt = 0 and I = 0) shows that both equations become identical with K = kl/k2. 2.5 CONDUCTIVITY AS A FUNCTION OF OXYGEN PRESSURE Most studies of the defect properties of ZnO conclude that interstitial zinc ions and electrons act as the dominating defects.The electroneutrality condition together40 CONDUCTIVITY OF ZnO with the law of mass action predicts a % power relation between oxygen pressure and conductivity. This relation combined with eqn (2.14) and (2.22) yields an expression for the average conductivity in a neck at equilibrium in darkness ; kin, * k2.f CJ = ooP&oo -Poz exp [-q+/kT] (2.23) where go stands for the conductivity of ZnO at 1 bar of oxygen (1 bar = lo5 N m-2 = lo5 Pa). The surface potential 4 is a function of the oxygen pressure. Their relation results from the eqn (2.10) and (2.22) : (2.24) Eqn (2.23) together with eqn (2.24) determine the average conductivity against oxygen pressure.A calculated pressure dependence is plotted in fig. 7, while in "7 to' a oxygen pressure/bar FIG. 'I.-Equilibrium conductivity of a neck region as a function of the oxygen pressure. kl = 1.46 x 10-19 cm3 bar-* s-l, kz = 9.00 x s-l, f = 5.62 x 10-411cm. fig. 8 an experimental curve is shown; the latter was measured at 540 K. Above bar the conductivity drops strongly but is not accurately reproducible. This is indicated in the figure with errors bars. At low oxygen pressure the experimental curve follows the predicted +-power law in a reproducible way. I f 12 - 4 I s 3 li4- 3 12 10 -88 IG8 1 2 lo4 16 loo oxygen pressurebar FIG. 8.-Equilibrium conductance of an experimental ZnO layer as a function of the oxygen pressure. NMB sample at 540 K.N.M. BEEKMANS 41 From the time constant for the conductivity change at low oxygen pressures of ~1 h a self diffusion coefficient for zinc of cm2 s-l has been derived. NO values for zinc diffusion at 540 K have been reported but extrapolated literature values for the self diffusion of zinc in ZnO ranges from to cm2 s-1.13-15 The rate of the conductivity change during evacuation of the space above a sample can be enhanced considerably by illumination with U.V. light. After illumination for a short period the conductivity remains nearly constant at a much higher conductivity level. This proves that the rate at which the conductivity increases in darkness is limited by the desorption reaction (2.2) and not by the interaction between surface and gas atmosphere.This was one of the presumptions of section 2.0. 3. EFFECTS OF A DISTRIBUTION IN GRAIN AND NECK SIZE Section 2 dealt mainly with the changes in the average conductivity in a single neck or in layers with uniform particle size. However, experimental layers are built-up from grains of an ill-defined shape and with a certain spread in grain size. The ZnO powder used in the experiments follows closely a log normal distribution with a mean Stokes diameter of 0.64 pm and a standard deviation of 1.46. Although we do not have direct knowledge of the neck size distribution in experimental ZnO layers, it seems fair to assume that the neck size distribution shows some resemblance to the grain size distribution. In this section we assume that the shape of the neck size distribution and the shape of the grain size distribution are the same.Current flow in a ZnO powder layer is possible only if uninterrupted paths for current fiow can be found. Below a certain fraction of conducting necks, the so-called percolation limit, the probability that such paths exist is very low. The conductivity of a powder consisting of a mixture of conducting grains and of non-conducting grains or cavities In this equationp stands for the fraction of the conducting grains in the system while pc is the percolation limit. The power m ranges for the different authors from 1.5 to 2.16-19 According to Scher and Zallen 2o the percolation limit for a three- dimensional array is M 0.1 5 of the occupied volume and for a two-dimensional array M 0.44 of the occupied area.The experimental layers used have a thickness of x 5-8 gains and are therefore not covered by the definition of a three-dimensional layer or by that of a two-dimensional layer. Consequently, the percolation limit for these layers will depend on its thickness. In darkness only a limited fraction of the grains are conductive. Hence, we may expect a strongly non-linear relationship between dark conductivity and layer thickness. This effect is observed experimentally. The necks between the grains can be grouped into three catagories. Firstly, the very large necks, which are always wider than the depletion thickness. Grains interconnected by such necks can always contribute to a conduction path through the layer. Secondly, the moderately size necks, which are almost completely depleted in darkness and consequently have a low dark conductivity.Under illumination the depletion layers in the necks diminish and these necks can then form part of a conducting path through the layer. The third category compreses the necks which are small and heavily overdepleted. These necks will never contribute to the conductivity at the light levels considered. Assuming a conductivity under iUurnination of -80 % of the single crystal value and no dark conductivity, the fraction of the conductiiig and of the light sensitive grains in a layer can be estimated. Fig. 9 shows the resulting neck size distribution based on a space percolation limit of 0.25 and a packing density of 0.55. The fraction42 CONDUCTIVITY OF ZnO of permanently conducting grains in fig.9 is 34 %. Under illumination the fraction of conducting necks increases because of the contribution of the light-sensitive grains (19.5 %). 2.0 T 0.5 0.0 , 0.00 0.05 0. LO neck radiuslpm FIG. 9.-The estimated neck size distribution of the ZnO powder used. A ZnO layer containing up to -34 % conducting necks remains in a low conductive state in darkness. A fraction of light- sensitive grains of -20 % is sufficient to cause a considerable photo effect. Examination of fig. 9 shows that only necks within a small range of radii are light sensitive. Furthermore, the major part of these light sensitive grains have radii smaller than the thickness of the depletion layer in darkness. Therefore, these necks are more or less overdepleted in darkness.As discussed before, overdepletion causes a drop in the photoconductivity, particularly at low light levels. 4. MAXIMUM PHOTOSENSITIVITY In a neck the acceptor or recombination centres are not homogeneously distributed throughout its volume but located on the surface. Nevertheless we may treat such a neck as a simple secondary photoconductor since the diffusion length of the electrons and the holes is more than the neck radius. In a ZnO powder layer reflection of light on the layer, low quantum efficiency, etc. prevent optimal conversion of the incident radiation. Since the influence of all these effects is difficult to estimate, we restrict ourselves to the calculation of an upper limit for the photosensitivity. All effects that reduce the photosensitivity, such as reflection and scattering of photons, are ignored.The quantum efficiency will be taken as one ; the lifetime of the electrons is assumed to be unlimited. Furthermore we assume the ZnO powder layers to be 100 % dense. Light incident on a semiconductor is absorbed according to : A = Zo[l -exp ( - a x ) ] , (4.1) where A is the energy absorbed in a layer with a thickness x, 1, is the incident radiation at the surface ( x = 03, and a the absorption coefficient.N. M. BEEKMANS 43 In a thin sheet of ZnO, electron-hole pairs are generated by the absorption of photons with an energy greater than the band gap of 3.2 eV. The holes recombine at the recombination centres on the surface leaving the electrons free to move. The increase in the free electron concentration results in an increase in the conductivity of the layer.The rate at which the conductivity increases at a depth x is : where Eg is the band gap in eV. Allowing for the geometry and the positions of the electrodes, integration of eqn (4.2) yields the rate of conductance change for a given layer at a certain illumination level. Using the geometry of the experimental layer quoted in section 3 and a mobility of 70 cm2 V-l s-l 21 and an adsorption of 10-4,22 we arrive at the rate of conductance change plotted in fig. 6 . The theoretical maximum rate of conductance change is - 3.5 decades higher than experimentally found, but the calculated curve is based on rather optimistic assumptions. 5. DISCUSSION In section 2 a model has been proposed for the conductivity in a single neck based on the chemisorption and photodesorption of oxygen ions at the surface.Together with the percolation theory this model seems to explain qualitatively nearly all well- established conductivity effects in ZnO powder layers. However, this does not imply that all the underlying assumptions are necessarily correct. For instance, we have ignored the possibility of an intergrain 24 The alignment of the crystal lattices of two adjacent grains is, in general, very poor and will give rise to a barrier in the neck. In section 3 it is shown that the charge density in the space charge region is smaller in an overdepleted neck than in the adjacent grains. This effect will cause also an intergrain barrier either due to the difference in surface potential or due to the creation of a potential barrier inside the neck.In the light-sensitive necks this intergrain barrier exists only in darkness or at low light levels and disappears completely under stronger illumination. 5.1 SURFACE ACTIVATION Photosensitivity has been defined as the rate of conductivity change under illumination. The photosensitivity will be influenced by the method of sample preparation and by the gas atmosphere. Variations in the sample preparation may change the nature of the chemisorbed species. More probable, however, is that certain constituents of the gas phase or of the chemisorbed layer activate or deactivate the chemisorption of the oxygen. For the simple case of 0- adsorption on a fixed number of sites the effects of activation of the surface reaction are relatively easy to understand.The surface reaction can be enhanced or slowed down by some treatment, but in equilibrium the sum of all electrochemical potentials in the surface reaction is zero [eqn (2.20)]. In section 2.4 the equilibrium surface occupation was calculated for this condition. Since the constant Kin eqn (2.22) contains fundamental constants and standardized material constants only, it has to be considered as a characteristic constant for adsorption on ZnO surfaces. The value of this constant is not influenced by any kind of surface activation. The rate constants kl and k2 may change over several decades as a result of surface activation, but the relation K = k1/k2 fixes their ratio. Since rate constant k3 was assumed to be proportional to k2 the photosensitivity of the layer will increase with an increase of the adsorption and desorption rates.44 CONDUCTIVITY OF ZnO The reasoning given above is valid for those types of activation of the chemi- sorption where the activator has an intermediate function only.An example could be: +020 + e; + H20, + 0; + H20, H20g + H207. ( 5 4 It is also possible that the surface adsorption involves another molecule. An example of such a reaction is : go,, + e; + 3H20, + OH;. When eqn (5.2) is valid, the equilibrium surface occupation is no longer a constant but varies with the vapour pressure of water. Nevertheless at a given vapour pressure of water the number of surface sites is fixed. Hence the theory developed in section 2 is fully applicable.Complications may occur when all sites available for adsorption are no longer equal but consist of sites of type I with properties different from sites of type IL2’ This can give rise to effects which the theory presented here cannot account for. For example, suppose chemisorption takes place by fast adsorption on sites of type I, followed by a slow conversion to sites of type 11. Under certain circumstances this will give rise to a peak in the conductivity response to illumination. Such peaks in the conductivity response to illumination. Such peaks in the conductivity plot have been observed by several authors.26* 27 5.2 CONDITIONS FOR MAXIMUM PHOTOSENSITIVITY For the highest photosensitivity a ZnO powder layer must be built up as regularly and uniformly as possible.Ideally, the layer would consist of spherical grains, densely packed in a layer of well-defined thickness, interconnected via necks identical in geometry and operated at an oxygen pressure level which depletes the neck completely in darkness without causing overdepletion. Deviation from this ideal situation deteriorates the photoconductive properties. Overdepletion, for example, reduces the photosensitivity considerably, particularly at low light levels. Since ZnO layers are built up from grains not uniform in size or shape avoidance of overdepletion demands operation at a fairly high conductivity level. Hence, illumination with light of considerable intensity is necessary to change the conductivity at this level substantially. Operating the layer at a lower light level without causing overdepletion is only possible if a material is chosen whose grain size distribution has a smaller standard deviation.6. CONCLUSION The conductivity of a ZnO powder layer appears to be controlled by the neck conductivity, which in turn is controlled by chemisorption of the charged species and can be described as a first order reaction in which oxygen from the surrounding gas atmosphere and electrons extracted from the semi-conductor are involved. Comparison between measurements of the oxygen pressure dependence of the conductivity in ZnO layers and calculation of the thermodynamic equilibrium at the surface has confirmed the feasibility of a model based on surface reactions. The oxygen pressure dependence found experimentally is in agreement with a defect model in which singly charged zinc or oxygen defects and electrons are dominant.The effects predicted by the theory are in fair agreement with the experimental results, particularly at high light levels. Treating the ZnO powder layer as a secondaryN. M. REEKMANS 45 photoconductor has enabled us to calculated. a maximum rate of conductivity change for ZnO powder layers. The rate of conductivity change is for certain applications a criterion for the photosensitivity of the layer. It is shown that a substantial fraction of the necks between the grains would be overdepleted in darkness and at low light levels. Under these conditions the photo- sensitivity of powder layers would be reduced strongly. Maximum photosensitivity in a powder layer requires a regular and densely packed layer of well-defined thickness consisting of equally sized spherical grains and operated at an oxygen pressure which just allows complete depletion in darkness.Powder layers essentially consist of grains with a certain distribution in size and geometry and have an irregular structure. From this point of view powder materials seem not to be the most obvious choice for the realization of a highly sensitive photoconductive layer. The author thanks his colleagues, in particular, Dr. J. E. Ralph, Dr. J. W. Orton, Mr. I. C. P. Millar and Dr. P. S. Clarke for helpful discussions. Most of the experimental data are based on measurements by Mr. I. C. P. Millar on a sample prepared by Mr. M. J. Plummer. D. A. Melnick, J. Chem. Phys., 1957,26,1136. 6. Heiland, E. Mollwo and F. Stockmann, in Solid State Physics, ed. F . Seitz and D. Turnbull (Academic Press, N.Y., 1959), vol. 8, p. 275. S. R. Morrison, in Aduunces in Catalysis, ed. W. G. Frankenburg, V. I. Kamarewsky and E. K. Rideal, (Academic Press, New York, 1955), vol. 7, p. 259-300. A. R. Hutson, in Semiconductors, ed. N. B. Hannay (Reinhold, New York, 1960), p. 543. €3. S. Agayan, I. A. Myasniko and V. I. Tsivenko, Russ. J. Phys. Chem., 1973, 47, 553. J. W. Orton, personal communication. A. v. d. Ziel, in Solid State Physical Electronics (Prentice-Hall, 1968). ' K. Tanska and G. Blyholder, J. Phys. Chem., 1972,76,3184. J . 0. Cope and I. D. Campbell, J.C.S. Furuday I, 1973, 69, 1. H. J. Engell, in Hulbleiterprobleme, ed. W. Schottky (Vieweg, 1954), vol. 1. l o R. M. ShafFert, Electrophotography (Focal Press, 1965). l 2 H. Rickert, Einfiihrurig in die Elektrochemie fester Stoffe (Springer, 1973), p. 42. l3 F. Munnick, Nuturwiss., 1955, 42, 340. l4 E. A. Secco and W. J. Moore, J. Chem. Phys., 1955, 23,1170; 1957,26, 942. Is W. J. Moore and E. L. Williams, Disc. Furuday SOC., 1959, 28, 86. l 6 S. Kirkpatrick, Phys. Rev. Letters, 1971, 27, 1722; Rev. Mod, Phys., 1973, 45, 574. l 7 R. B. Stinchcombe, J. Phys. C, 1974,7, 179. J. P. Straley, J. Phys. C, 1976, 9, 783. l 9 B. Abeles, H. L. Pinch and J. I. Gitteman, Phys. Rev. Letters, 1975, 35, 247. 'O H. Scher and R. Zailen, J. Chem. Phys., 1970,53,3759. 21 J. R. Miller, Phys. Rev., 1941, 60, 980. K. Intemann and F. Stockmann, 2. Physik, 1952, 2 2 Yu. S . Leonov, Optics and Spectroscopy, 1962, 12, 143. 23 J. C. Slater, Phys. Reu., 1956, 103, 1631. 24 J. W. Orton, A. H. M. Kipperman and J. A. Beun, J. Phys. D, 1976,9, 69. 2 5 M. Breysse, B. Claude1 and P. Meriaudeau, J.C.S. Furuduy I, 1976, 7 2 , l . 26 E. Molinari, F. Oramarossa and F. Paniccia, J. Catalysis, 1965,4,415. 27 H. A. Papazian, P. A. Fiinn and D. Trivich, J. Electrochem. Soc., 1957, 104, 84. 131, 10. (PAPER 71127)

ISSN:0300-9599    

DOI:10.1039/F19787400031

出版商:RSC    

年代:1978

数据来源: RSC

摘要:

Heats of Hydrogenation of Large Molecules Part 2.-Six Unsaturated and Polyunsaturated Fatty Acids BY DONALD W. ROGERS,* OTHO P. A. HOYTE AND RICKEY KAM C. Ho Department of Chemistry, The Brooklyn Center, Long Island University, Brooklyn, New York, 11201 U.S.A. Receiced 7th March, 1977 We have determined the heats of hydrogenation of the C16 and CI8 unsaturated and poly- unsaturated fatty acids, palmitoleic, oleic, elaidic, linoleic, linelaidic and Iinolenic aCids. This paper reports and interprets the results in the light of previous experimental measurements and theoretical predictions. Heats of formation follow from Hess’ Law addition to the reliable values of the heats of formation of the hydrogenation products, hexadecanoic (palmitic) and octadecanoic (stearic) acids. Our results are generally in serious disagreement with the scattered experimental data and predictions gleaned from the literature and represent, we think, a significant improvement over them.Prior to 1930, despite chemical 1. and X-ray evidence to the contrary, oleic acid was widely regarded as the trans-isomer of 9-octadecenoic acid and elaidic acid was regarded as the cis-form. In that year, Keffler investigated the problem from a thermochemical point of view 4* and argued that the configurations are reversed. His conclusion was based on the relative heats of combustion of the isomers, and as abundant subsequent evidence shows, was correct. We feel, however, that the experimental problems of purifying .and preserving samples of fatty acids were so great as to make his conclusion fortuitous and his numerical data suspect.The same is true of the much earlier thermochemical results of Stohmann who also arrived at the correct relative stability of the isomers. More recently, the only thermochemical studies on unsaturated fatty acids have been those of Suito and Aida 7* who estimated the heats of hydrogenation of oleic acid and its methyl ester by a kinetic method and Omil’chenko, who predicted the heats of formation of several saturated and unsaturated fatty acids 9 9 lo “ from molecular structure ”. In contrast to the unsaturated fatty acids, the common saturated fatty acids have been studied very thoroughly. Combustion studies by Adriaanse, Dekker and Coops 11* l 2 and Swain, Silbert and Miller l3 are in good agreement and would seem to be among the most reliable thermochemical data available on large molecules. These data are supplemented by the fusion data of Lebedeva.14 The existence of reliable heats of formation of saturated fatty acids makes it desirable to know the heats of hydrogenation of the corresponding unsaturated and polyunsaturated acids.Heats of hydrogenation, which may be determined with good accuracy on very small samples, lead directly to the heats of formation of the unsaturates by Hess’ Law addition, thus circumventing the meticulous experimental procedures necessary to determine accurate heats of combustion for molecules of this size. 46D. W. ROGERS, 0. P . A. HOYTE AND R. K . C. HO 47 EXPERIMENTAL APPARATUS The apparatus used was as previously described l5 except that the calorimeter was made hydrogen-tight with a rubber gasket instead of silicone sealent.REAGENTS All fatty acids were obtained from Analabs (North Haven, Connecticut 06473) and certified by the manufacturer to be 99+ % pure as determined by g.l.c., t.1.c. or both. Sample treatment was as previously described l5 and the sources and purities of the other reagents have been given.16 PROCEDURE Experimental data were gathered as previously described.16* l7 80 mm3 of a -28 % solution ( - 70 pmoles) of the unsaturated fatty acid in n-hexane were injected into a calorimeter containing hydrogen at 2atm pressure and a stirred slurry of 5 % Pd on charcoal. For acids containing one double bond, these injections were alternated with identical injections of an approximately equimolar solution of 1-hexene in n-hexane.For acids containing two or three double bonds, the concentration of hexene was doubled or tripled so that the standard 1-hexene solution was approximately thermochemically equivalent to the unknown acid. Hydrogenation brought about a temperature change of ~ 0 . 2 K. Assuming the heat of hydrogenation of 1-hexene to be known (-126.4kJmol-' = - 30.22 kcal mol-I) from the combustion studies of Bartolo and Rossini,18 comparison of the temperature rise per mg of the 1-hexene standard to that of the unknown acid leads directly to the heat of hydrogenation of the acid. The specific g.1.c. procedure for fatty acid methyl esters l5 for establishing purity of the reaction product (evidence for completeness of reaction) was modified for free fatty acids by switching to a 6' 10 % SP-216-PS stationary-phase column. The supporting medium was Supelcoport and the prepared stainless steel Q in.column was obtained from Supelco (Bellefonte, Pensylvania 16823). Our reason for switching to the more polar stationary phase rather than converting the free acids to their methyl esters prior to g.1.c. separation was that we wished to subject the reaction product to a minimum of chemical treatment which might obscure detection of trace amounts of unsaturation. Diagnostic tests for unsaturation were designed as before and indicated complete hydrogenation in each case, as elaborated in the discussion section. The carrier gas was helium at -50 psi and the column temperature was 180 to 200°C.RESULTS AND DISCUSSION RELIABILITY At present, we feel that the overall error is within & 1 % which is typical of what earlier workers report for smaller molecules. Clearly, this does not compare with the relative error reported in good contemporary combustion calorimetry. Coinbustion calorimetry suffers one serious drawback, however. As combustion methods are applied to larger molecules, the absolute error of any combustion calorimetric method becomes larger. Restricting our attention to hydrocarbons for the moment, a four carbon chain might have an enthalpy of combustion of a little less than 3000 kJ mol-1 but a 16 carbon chain would have a heat of combustion four times that value. Given a constant relative error in kJ g-l, the absolute error of the second combustion is four times that of the first.This problem is especially serious because the structural information one wishes to deduce from thermochemical data usually depends on small differences in enthalpies of formation of the molecules under comparison, two cases in point being determination of cis-trans isomerization enthalpies and strain enthalpies.48 HEATS OF HYDROGENATION Despite the larger relative error of hydrogen calorimetry, it is clear that if reason- ably accurate hydrogenation data can be obtained, the enthalpy difference between a molecule having a heat of hydrogenation of 125 kJ mol-l and an isomer having a heat of hydrogenation of 120 kJ mol-I can be more confidently compared than can heats of combustion of 12 000 and 11 995 kJ mol-I.In summary assessment of the method, its principal advantages are speed, simplicity and the requirement of only a few mm3 of sample per injection, thus permitting sample purification by g.1.c. and related micromethods. Its principal drawback is a relative error of about rfi 1 % which can be improved upon by making the reaction time faster and instrument response time less so as to shorten extrapola- tions on the temperature-time curve. We believe both of these improvements are possible. DIAGNOSTIC TESTS Immediately upon concluding a series of hydrogenations, tlie calorimeter was dismantled, the catalyst filtered off and the calorimeter fluid containing all reaction products was set aside for analysis. A sample of stearic or palmitic acid was intentionally contaminated with a few percent of the unsaturated fatty acid under study and subjected to g.1.c.analysis. In each case, we obtained good separation of peaks for the saturated and unsaturated components of the solution. Next, the reaction products were subjected to analysis under identical conditions. Contaminated stearic or palmitic acid was injected before the calorimcter fluid of interest rather than in the reverse order so as to establish the optimum conditions for separation. Upon injection of calorimeter fluid, we observed, in addition to the hexane peak, a strong peak at the retention time of saturated acid due to the presence of the reaction product with a distinct minor peak at the retention time of the unsaturated acid. Thus, the preliminary indication was that hydrogenation was incomplete, a result difficult to reconcile with the excellent agreement of the heats of hydrogenation between the acids (see below) and tlie esters previously rep0rted.l If hydrogenation had been incomplete for the acids and complete for the esters, the acid values should be low.In fact, they are equal to or slightly higher than the heats of hydrogenation of the esters. Further g.1.c. investigation of solutions of saturates and unsaturates in hexane showed that injection of a pure unsaturated acid resulted in a chromatogram with an unexpected saturate peak and that injection of a pure saturated acid resulted in a chromatogram with an unexpected unsaturated acid peak. Repeated injection of either pure acid in hexane solution caused the anomalous peak to decrease in height.Our conclusion, supported by the column manufacturer's descriptive bulletin,20 was that both acids were being adsorbed at the metal injection inlet and being released little at a time on subsequent injections, causing the anomalous peaks. Accordingly, we injected repetitive samples of Calorimeter fluid after an intentioilally contaminated sample had been run and observed the behaviour of the peak due to unsaturated acid. The anomalous peak decreased in size until, after five or six injections, it disappeared altogether. The last discernible peak had an area which was of the order of a few tenths of a percent of the peak due to the saturated acid. Further injections of calorimeter fluid brought about no change in the chromatogram and no trace of the anomalous peak.We believe that hydrogenation was complete. In a few cases, we started a series of hydrogenation runs like those from which we drew our quantitative data but we withdrew aiiquots from the calorimeter between runs for g.1.c. analysis. The results were negative for unsaturated acid.49 D . W. ROGERS, 0. P . A . HOYTE AND R . K . C. HO CATALYST ALTERATION As we found to be true of methyl esters, the first few injections of unsaturated fatty acids produced heats of hydrogenation which were more negative than expected (see discussion). We take this to be due to exothermic adsorption of the saturated reaction product on the catalyst or, more probably, on the charcoal support. (5 % palladium on charcoal was used to make the catalyst slurry).As was true of the esters, this exothermic interference faded out after four or five injections and results calculated from the sixth injection on were constant at a plausible AHh of - - 124 kJ mol-1 for the cis-monounsaturated acids and -4 kJ lower for the trans-forms. Accordingly, the results shown in table 1 were calculated from runs after the sixth in any series. TABLE HEATS OF HYDROGENATION OF SIX UNSATURATED FATTY ACIDS AHh per double bond fatty acid AHh/kJ mol-1 a /kJ mol-1 oleic acid - 123.65 1.6 - 123.65 1.6 oleic acid -125.150.8 -125.lrfi0.8 elaidic acid - 120.252.0 - 120.2+2.0 linoleic acid -254.4+ 1.5 - 127.250.8 linolenic acid - 380.2+ 1.9 - 126.75 0.6 palmitoleic acid -125.1_+1.0 -125.1kl.O Iinoelaidic acid -248.8+0.5 - 124.4rfi0.3 a 1 kcal = 4.184 kJ In contrast to the methyl esters, however, there was a limit beyond which the catalyst charge was no longer useful.After sixteen to twenty pairs of alternate injections of 1-hexene and acid, kinetic lag and decreased potentiometer deflection were noted for the standard. Response for acid injections remained normal. This could be due merely to our having exceeded the solubility limits of the product stearic (or palmitic) acids which are not very soluble in hydrocarbons.21 We speculate that the polar stearic acid molecules produced at the catalyst surface tend to agglomerate about the catalyst particles as the solubility limit of stearic acid in hexane is approached. Agglomeration may prevent approach of 1 -hexene on the next injection. The 1-hexene standard, being nonpolar, is not able to compete on an equal basis with acid molecules so that its hydrogenation is retarded, the recorder curve is altered and extrapolation produces low results.Subsequent injections of acid, however, add polar molecules to the system which compete successfully for the catalyst surface with the molecules already there. The curve shape and recorder responses are therefore unaltered for the acid. This behaviour is clearly indicated by altered recorder response and appears well after a useful series of calorimetric runs has been made. A broad " window '' exists between initial adsorption effects and deterioration of the standard curve, thus collection of data as shown in table 1 was possible. Each entry in table 1 represents the arithmetic mean of six experimental data and the error limits are the standard deviations of all six results from their mean.Translation from the nonsystematic nomenclature which is almost universal in fatty acid chemistry is as follows : palmitoleic, olcic, elaidic, linoleic, linoelaidic and linolenic acids are cis-9-hexadecenoic, cis-9-octadecenoic, irans-9-oct adecenoic, cis-9-cis- 1 2-octadecad- ienoic, brans-9-trans- 12-octadecadienoic and cis-94s- 12-cis- 1 5-octadecatrienoic acids respectively.50 HEATS OF HYDROGENATION COMPARISON WITH PREVIOUS WORK Suito and Aida have obtained the value of - 156 kJ mol-1 for hydrogenation of oleic acid over raney nickel by a kinetic m e t h ~ d . ~ A subsequent study yielded - 149 kJ mol-l for both oleic acid and methyl oleate.8 Both of these values seem too negative by comparison with our data.We have encountered exothermic adsorption interference in preliminary studies which give an apparent heat of hydrogenation which is too negative by 20 to 24 kJ mol-1 [see ref. (1 5) for a discussion of adsorption effects]. Table 2 shows the heats of formation and fusion taken from Domalski's critical review 2 2 and table 3 shows the heats of formation of the unsaturated acids by Hess' law addition to the values for the heat of formation of the liquid palmitic or stearic acid listed by Domalski. These in turn were taken from the combustion data of TABLE 2.--"EATS OF COMBUSTION AND FUSION OF STEARIC AND PALMITIC ACIDSa AHc/kJ mol-1 AHf/kJ mol-1 at 298 K A Hfus at 298 K fatty acid (crystal) /kJ mol-1 (liquid) stearic acid - 11280 58.6 - 889.1 palmitic acid - 9978 53.1 - 838.5 a From the review of Domalski.32 Adriaanse, Dekker and Coops 11* l2 and fusion data of Lebedeva.14 Also tabulated in table 3 are predictions by Omil'chenko based on a bond-energy scheme and heats of formation calculated from the heats of combustion of unsaturated fatty acids by Keffler.The results we obtained for the fatty acid methyl esters l5 were based on a value of - 123.7 W mol-1 for the heat of hydrogenation of the 1-hexene standard. This value is in error by 2.76 kJ mol-I. When comparing the present data with those for the esters, each ester datum should be multiplied by the factor (126.4/123.7)4.184. TABLE 3.-HEAT OF FORMATION OF UNSATURATED FATTY ACIDS fatty acid AHt a /kJ mol-1 AHrb /kJ mol-1 oleic acid -764.8 C -710.2 -748.5 (I) -783.2 (s) elaidic acid - 769.0 -910.8 (s) linoleic acid - 634.7 - 603.1 linoelaidic acid - 640.2 linolenic acid - 508.8 - 485.9 palmitoleic acid - 713.4 - 656.7 a Data of Omil'chenko, ref.(10) ; b from data of Keffler, ref. (5) ; C average of two sets of experi- ments. One area in which we expect to find data comparable with those in table 1 is that of cis-trans isomerism studies. The appropriate data involve transition from a reactant to a product which is in the same or nearly the same physical state. Kistiakowsky, et aZ.23 observed the vapour to vapour transition of cis to trans 2-butene to be -4.0 kJ mol-l, Turner et ~ 1 . ~ ~ obtained -3.6 kJ niol-l for the isomerization of 1,1,8,8-tetramethy1-4-octene from the pure liquid to dilute aceticD. W.ROGERS, 0. P. A . HOYTE AND R. K. C. HO 51 acid solution and Franklin estimated the average cis-trans isomerization energy from the vapour to the vapour state as -5.23 kJ mol-l. In previous work on the methyl esters of unsaturated fatty acids, we found the isomerization enthalpies of methyl oleate to methyl elaidate to be -3.6 kJ mol-1 on one set of trials and -4.6 kJ mol-1 on another. Comparison of the value for elaidic acid in table 1 with the two values for oleic acid yields an isomerization energy of -3.4 kJ mol-1 from one experimental value for oleic acid and -4.9 kJ rno1-l for the other. These values are in excellent agreement with our values for the esters and other worker’s values for similar isomerizations of smaller molecules.In contrast, we have the value of - 128 kJ mol-I isomerization enthalpy for the oleic acid to elaidic acid conversion calculated from Keffler’s combustion data on the two acids5 This remarkable value was used by Keffler to support his (correct) assignment of cis-trans isomerism for oleic and elaidic acids. With the advantage of hindsight and the studies of Kistiakowsky and Turner, however, this value has become totally unreasonable and we must now use it as grounds to reject his numerical data for the thermochemistry of the unsaturated fatty acids. Subtracting the value of the heat of hydrogenation of linoleic acid from that of linolenic acid, we obtain - 125.8 kJ mol-1 for the partial hydrogenation of linolenic to linoleic acid.Proceeding by the same method, we find the following step-wise hydrogenation sequence : - 125.8 - 130.7 - 125.1 linolenic I_+ linoleic -129.; oleic We feel that, in view of the cumulative error encountered in determining partial heats of reaction by difference, that these data are quite self-consistent. In contrast, the predictions of Omil’chenko, taken in combination with Adriaanse, Dekker and Coops’ value for the heat of formation of stearic acid yield stearic. - 117.2 - 107. I - 179.1 linolenic --+ linoleic + oleic - stearic. These values are neither self-consistent nor in agreement with our experimental results. We wish to acknowledge support of this work by the National Institutes of Health. R. Robinson and G. M. Robinson, J. Chem. SOC., 1925,127,175 ; 1926,2204.T. P. Hilditch, J. Chem. SOC., 1926, 1828. A. Muller and G. Shearer, J. Chem. Soc., 1923, 123, 1356. L. J. P. Keffler, J. Phys. Chem., 1930,34, 1319. L. J. P. Keffler, Rec. Trav. chim., 1930,49,415. F. Stohmann, 2. Phys. Chem., 1892,10,416. E. Suito and H. Aida, Bull. Int. Chem. Res. Kyoto Uniu., 1950, 22, 82 (C.A., 46, 8489g). E. Suito and H. Ada, J. Chem. Soc. Japan (Ind. Chem. Soc.), 1951,54, 765 (C.A., 47,7795~). F. S . Omil’chenko, Masluzhir. Prom., 1965,31,23 (C.A., 63, 17221e). lo F. S. Omil’chenko, Izv. Vyssh. Ucheb. Zaned., Pishch. Teknol., 1967, 37. ‘l N. Adriaanse, H. Dekker and J. Coops, Rec. Trav. chim., 1964, 83, 557. l2 N. Adriaanse, H. Dekker and J. Coops, Rec. Tmv. chim., 1965,84, 393. l3 H. A. Swain, Jr., L. S. Silbert and G. G. Miller, J. Amer. Chem. SOC., 1964, 86, 2562. l4 N. D. Eebedeva, Zhur. $2. Khim., 1964,38,2648. l5 D. W. Rogers and N. A. Siddiqui, J. Phys. Chem., 1975,79, 574. l6 D. W. Rogers and S. Skanupong, J. Phys. Chem., 1974, 78,2569. l7 D. W. Rogers, P. M. Papadimetriou and N. A. Siddiqui, Mikrochem. Actu, 1974, 937. H. F. Bartolo and F. D. Rossini, J. Phys. Chem., 1960,64, 1685. l9 J. D. Cox and G. Pilcher, Thermochemistry of Organic and Organometallic Compounds (Academic Press, New York, N.Y., 1970). 2o Supelco, Inc., Fatty Acid Analysis, Bulletin 727.52 HEATS OF HYDROGENATION 21 K. S. Markley, Fatty Acids : Their Chemistry and Physical Properties (Interscience, New York, 22 E. S. Domalski, J. Phys. Chem. Ref. Data, 1972, 1, 221. 2 3 G. B. Kistiakowsky, J. R. Ruhoff, H. A. Smith and W. E. Vaughan, J. Amer. Cfieni. Soc., 24 R. B. Turner, A. 0. Jarrett, P. Goebel and B. J. Mallon, J. Amer. G e m . Soc., 1973, 95, 790. 2 5 J. L. Franklin, Znd. and Eng. Chem., 1949, 41, 1070. 1947), p. 190 ff. 1935, 57, 876. (PAPER 7/401)

ISSN:0300-9599    

DOI:10.1039/F19787400046

出版商:RSC    

年代:1978

数据来源: RSC

摘要:

Kinetics of Gas Phase Electron-Ion Recombination by NO+ + e- + N+ 0 from Measurements in Flames BY NIGEL A. BURDETT AND ALLAN N. HAYHURST" Department of Chemical Engineering and Fuel Technology, University of Sheffield, Mappin Street, Sheffield, S1 3JD Received 25th March, 1977 Mass spectrometric measurements of ion concentrations in the burnt gases of flames of either CzH2 + O2 + N2 + occasionally trace amounts of NO or H2 + O2 + N2 with small additions of C2Hz and NO have enabled the rate coefficient, kl, for electron-ion recombination in reaction (I) NO++e- + N+O (1) to be determined. Such measurements have been made for a wide variety of flame conditions over the temperature range 1820 to 2650K and indicate that kl changes from 2.3xlO-' to 1 . 4 ~ lo-' ion-' cm3 s-l. At the lower temperatures kl varies as T-O*', but as at the hotter ones.There is evidence that circumstances can be devised in flames, when charged species are produced by chemi-ionization in the reverse of reaction (I), whose rate coefficient is found to be 6.7 x 10-l2 exp (- 31 9OO/T) atom-' cm3 s-l from 1820 to 2650 K. The NO+ ion is important in partially ionized systems containing nitrogen and oxygen, because of its stability and ease of formation from other ions. Thus ionization and recombination in hypersonic airflows or shock waves involve NO+ to a significant degree. In addition, NO+ plays an important role in the upper atmosphere and is sometimes present in hydrocarbon flames in amounts well above those for equilibrium. Measurements of the rate of dissociative recombination of NO+ with free electrons in reaction (I) NO++e- -+ N+O (1) have already been made and the results have been reviewed by Han~en.~ However, hardly any have been made under flame conditions, so that this work aims to remedy this and to check if the temperature dependence of k l , the recombination coefficient of (I), reported earlier ( k , varying as T-* for T > 2500K, but as T-% for T < 1000 K) holds in flames.Ions are produced in the reaction zone of a hydrocarbon-containing flame mainly by the primary chemi-ionization process : 5 CH+ 0 + CHO++e-, with CHO+ reacting rapidly by proton or charge transfer to a whole range of flame species, such as H20 and NO in reactions (11) and (111) : CHO++HzO 4 H,O++CO (W CHO++NO + NO++CO+H. (111) These H30+ and NO+ ions are, together with the free electron, the principal charged species to survive into the burnt gases of hydrocarbon The relatively small amount of natural neutral NO in the reaction zone means that the NO+ produced by reaction (111) is minimal, although this is not the case in C2H2/02/N2 flames7 or 5354 RECOMBINATION OF NO++e- ones of CO/O, with C2H2 and NO added.6 Another important source of NO+ is the forward step of which operates in the burnt gases of a flame.' This process can be sufficiently fast at the temperatures involved here to become balanced away from the reaction zone.Another possible route for the generation of NO+ is by chemi-ionization in the reverse of reaction (I). This occurs in shock tubes,2 but so far has not been established in flames.Ion recombination in the burnt gases of a flame containing H30+ and NO+ is by step (I), as well as reaction (V) whose kinetics have been m e a s ~ r e d . ~ ~ lo The study reported below aims to measure k, both directly and by comparison with the known rate coefficient k5 of reaction (V). H,O++NO + NO++H,O+H, (W H,O++e- -+ H+H+OH, 0') EXPERIMENTAL The flames were premixed ones of either H2 or CzH2 burnt at atmospheric pressure with O2 and Nz as diluent. The burner has been already described " 9 l2 and gave laminar cylindrical flames with an almost flat reaction zone. Flame compositions and temperatures are given in table 1, where it is seen that all those of H2 were fuel-rich, whereas the C2H2 ones had a wide range of unburnt stoichiometry and temperature for their burnt gases.Nitric oxide was occasionally added to the burner supplies from a N2 cylinder containing 1 % of NO, so that its maximum mole fraction in the unburnt gases was 0.007. Absolute measurements of hydrogen atom concentrations along the axis of each flame were made by the Sr+/SrOH+ technique.13 no 1 2 3 4 5 6 7 8 9 TABLE 1 .-DESCRIPTION OF FLAMES STUDIED unburnt composition ratios burnt gas C2H2 H2 0 2 Nz temp/K velocity/m s-1 1 .o 1.5 4.5 2630 22.9 1 .o 2.0 6.0 2650 23.1 1 .o 2.5 7.5 2590 22.6 1 .o 3.0 9.0 2490 21.7 1 .o 3.5 10.5 2380 20.7 1 .o 4.0 12.0 2200 19.2 3.12 1.0 5.77 1820 8.4 3.09 1.0 4.74 1980 11.4 3.18 1.0 4.07 2080 15.6 Concentrations of positive and negative ions were measured at various points along each flame by direct and continuous sampling into a quadrupole mass spectrometer.11* l4 Calibration techniques to arrive at absolute ion concentrations have been described before.ll Since the burnt gases of each flame have well characterised axial velocities, any distance from the reaction zone can be transformed into a time.Most observations were made in the region 5-25 mm from the reaction zone, to avoid disturbances of the flame by the sampling system l5 and the surrounding atmosphere. One difficulty with this work is that the process of sampling introduces cooling and a consequent falsification of mass spectra. This arises through ions reacting in the sample in the time of -1 ,us before all collisions cease.16- l7 For instance, hydrates of H30+ with up to four water molecules attached can be detected.They were assumed to be formed from the genuine flame ion 5 3 l6 H30+ during sample cooling, so that their concentrations were simply added to that of their parent, H30+. When NO was added to H2 flames, both NO+ and NO+.HzO were observed. For instance, [NO+]/[NO+.HzO] was measured to be 15N . A. BWRDETT AND A. N . HAYHURST 55 when sampling 10 mm downstream of the reaction zone of flame 7 using a chromium sampling nozzle l2 of diameter 0.06 mm. Under these conditions [H30+]/[H30+.HzO] was 2.9, with the lower value probably arising from the hydration of H30+ being faster than that of NO+. In any event, [NO+] was always corrected for hydrate formation. The other possible sampling disturbance is a shift in reaction (IV) for systems containing H30+ and NO+.This does not happen in CzHz flames without added NO, since reaction rates are then too slow.' However, it can occur in the hottest H2 flames (T > 2400 K) with NO as an additive: because [HI and [H,O] are much larger than in CzHz flames of similar temperature. This matter is referred to again below, but it should be noted here that only if the relative abundance of an ion does not depend on the nature of the sampling system (e.g. on the inIet orifice diameter), can it be assumed to be unaffected by sampling. RESULTS In CzH2 flames with no NO added, the principal positive ions in the burnt gases were H,O+ and NO+, with the free electron being by far the major negatively charged species. This is in striking contrast to H2 flames, where NO+ nearly always has a negligible concentration.The difference presumably arises from neutral NO being formed only by the Zel'dovich scheme l 8 in H2 flames, but by the " prompt " one as well in hydrocarbon systems." 19* 2o Typical ion profiles for H30+ and NO+ along the burnt gases are shown in fig. 1 for flame 5 (see table 1 for details). I \k 0 distance from reaction zone/= FIG. 1.-Measured ion profiles along the axis of flame 5 for 0.7 vol % of NO added (0, A) to the burner supplies and for none added (e, A). Some concentrations have been multiplied by the factors shown for clarity. e H30+( x 3), 0 H30+( x loo), A NO+, A NO+( x 3). H,O+ without NO added has a maximum concentration in the reaction zone and subsequently decays in the burnt gases by recombination with electrons in reaction (V) and by charge transfer in reaction (IV).Under these conditions [NO+] is initially small, but away from the reaction zone rises to a maximum, with subsequent dis- appearance by recombination with electrons in reaction (I) and possibly also in the reverse of reaction (IV). The initial rise in [NO+] is caused7 principally by its formation from H30+ in reaction (IV). Fig. 2 shows the profiles for H30+ and NO+ along the hotter C2Hz flame 3 at56 RECOMBINATION OF NO k+e- 2590 K. Here the maximum [NO+] has shifted into the reaction zone and also is larger than that for H30+, suggesting that increases in temperature and [NO] make a reaction such as (111) more effective than (11) in competing for the many available distance from reaction zone/mm FIG.2.-Concentrations of A, NO+ and 0, H30+ along the axis of flame 3 at 2590 K for no NO added. hydrocarbon In this flame the ratio [NQ-t-]/[H,Q+] is so high (at least 10) that, except very close to the reaction zone, the principal reaction is a loss of NO+ through dissociative recombination in reaction (1). This is described by with [e-] equalling [NO+] to within -5 %. Integration of eqn (1) yields the usual recombination expression : 1 1 + k i t [NO'] = for [NO+] = [NO+lo at time t = 0. Fig. 3 is a plot of l/[NO+] against distance along flame 3 using the data of fig. 2. As predicted by eqn (2), a good straight line can be fitted, enabling an estimate of kl to be made from the slope. The alternative recombination scheme in reactions (VI) and (VII) : NO++HzO = NO+.H20 (VI) NO+.H,O+e- -+ NQ+H,O will be considered below and rejected, mainly because the measured kl values are inconsistent with a two-step process involving the hydrate as intermediate.A more accurate way of arriving at kl is to take the measurements of [NO+] at various times from fig. 1 and, after an initial smoothing,21 numerically differentiate [NO+] with respect to time. The resulting values of d[NQ+]/dt at successive points along a Aame may then be combined with the measured [NO+] and [e-] (from [H30+] + [NQ+]) and substituted in eqn (1) to give kl at various distances along the bwnt gases. However, the increased computation time did not yield a significant improvement in accuracy, so that a simple measurement of the slope of a recombina-N. A .BURDETT AND A . N. HAYHURST 57 tion plot was preferred. Complications arose when [H,O+] was large compared with [NO+], because the charge transfer process (IV) affected the decay of NO+ and eqn (2) did not apply. This is especially true in the coolest C2H2 flame and all the H2 ones. To overcome this, NO was added to the C2H2 flames and the H, ones too, but here together with a small amount (<+ % by vol.) of C2H2 to increase primary ionization. 1 1 I 10 20 30 LO distance from reaction zone/mm FIG. 3.-Plot of l/[NO+] against axial distance along flame 3 using the data of fig. 2. The effect of this is shown in fig. 1 for the C2H2 flame 5 at 2380 K. Concentrations of [NO+] now very much exceed those of [H,O+] and the maximum [NO+] is now moved to the reaction zone.There appears to be no evidence for the operation of reaction (IV), since the [NO+] profile fits well to eqn (2), thereby establishing that (I) is the main reaction for NO+. In this case the above procedure for arriving at kl TABLE 2.-MEASURED VALUES OF kl FROM THE DIRECT METHOD AND FROM THE COMPARISON k5/kl. UNITS ARE cm3 ions-1 s-l 1 2630 1.2 2 2650 1.6 3 2590 1.4 4 2490 1.5 5 2380 1.7 6 2200 2.1 2.0 2.1 7 1820 1.7 2.4 8 1980 2.0 2.0 9 2080 2.0 2.0 flame temp/K 107k1 kslkl 107k1 may be used with confidence for all the C2Hz flames. The results of these measure- ments are given in the third column of table 2, these deriving from the average slope of the recombination plot in the region 5-25mm from the reaction zone. It was found that the measured kl did not vary at all with the diameter of the sampling hole, establishing that observations are not being falsified by sample cooling.It was necessary to adopt another approach for H2 flames, even with traces of C2H2 and NO added, because [H,O+] is significant compared with [NO+], the ratio58 RECOMBINATION OF NO++e- [H30+]/[NO+] being in the range 0.5 to 2. In this case the fall in the total positive ion concentration [P+] was observed, since --- d[p'l - (kl[NO'] + k5[H30'])[Pf] dt for [P+] = [NO+]+[H30+]. This leads to Thus in a flame in which [H,O+] and [NO+] are comparable, it should be possible to arrive at k5 and k l . Since any measurement of k5 is known lo to be affected by sampling, the following procedure was adopted here for H2 flames and the coolest flame of C2H2. The differential d[P+]/dt was obtained using the numerical procedures 10 0 I I 0.5 I .o I ;5 [HJO+I/"O+] FIG.4.-Experimental plots of - V(dlP+]/dz)/p+]WO+] against [H30+]/[NO+] for a range of flames as labelled. [P+] is the total positive ion concentration. mentioned above, using the fact that it equals Vd[P+]/dz, where V is the velocity of the burnt gases at distance z downstream of the reaction zone. Plots of the left hand side of eqn (3) against [H30+]/[NO+] are given in fig. 4 for flames 6-9. They are all fair approximations to straight lines. The value of kl was obtained from the ratio of the slope to intercept (= k5/kl) and the known lo k5 of 4.1 x ions-I mls-l for the flame temperatures used here. Such a procedure avoids a direct calibration of the mass spectrometer and the sampling difficulties occasionally lo associated with H30+.Table 2 lists both k,/kl and the kl values resulting from this approach in the third column. Once again these kl values were found not to vary with the size of the sampling inlet orifice. DISCUSSION The recombination coefficient kl has been measured using two methods : a direct one necessitating a calibration of the mass spectrometer and an indirect one involving a comparison with the already known k5. All the results from both approaches areN. A . BURDETT AND A . N. HAYHURST 59 plotted in fig. 5 as In kl against In T. First, it is seen from fig. 5 that results from the two approaches are in agreement with each other. This is encouraging both as far as the validity of the adopted calibration procedure is concerned and the assumption that k5 is constant at 4.1 x !O-7 ions-I cm3 s-l over this temperature range.Closer examination shows that In kl is not linear in In T, the best fit being curved, so that at 2650 K we have kl varying as T-195i,0*8, but as T-0-7i0-8 at 1800 K. The only other values of kl reported from flame work are 1.6rfrO.l x ions-' cm3 s-l, measured22 at 2500K from the decay of NO+ in a C0/02/N2 flame with small amounts of C2Nz added and 4.2f2.5 x ions-l cm3 s-l from a C2H2 flame at 2600 K. These independent observations are thus in agreement with the kl from this study, considering that the final kl values in table 2 each have an associated error of 60 %. The alternative recombination scheme to (I), involving steps (VI) and (VII), can now be considered.If the measured kl values are interpreted on the assumption that processes (VI) and (VII) are the relevant ones, we have kl = K6k7[H20], where K6 is the equilibrium constant of reaction (VI) and k7 is the rate constant of (VII). 16.0 * * - I ! I I I Now the C2H2 flames burnt have much smaller [H,O] in their burnt gases (by up to a factor of 10) than the H2 ones. That this is the case is manifested by NO+.H20 being hardly detectable in C2H2 flames. We conclude that the continuous curve of fig. 5, which covers measurements of kl in both types of flames, indicates that reaction (I), rather than (VI) and (VII), is operating, since otherwise a discontinuity arising from the dependence of kl on [H,O] should be apparent.In addition, the variation with temperature of the observed kl value has contributions from Ks and k7. The hydration energy 23 of NO+ is -82 kJ mol-1 and gives a significant change in K6 over the temperature range employed here. Admittedly, [H20] increases with temperature (as well as depending on the composition of the unburnt gases and the nature of the fuel) but the product Ksk,[H20] is not expected to vary as modestly and smoothly with temperature as fig. 5 indicates. Perhaps the most persuasive evidence against reactions (VI) and (VII) is that the low [NO+. H20] in CzHz flames would require k , to take values as unacceptably large as ions-' cm3 s-l at flame temperatures. We thus conclude that these measurements refer only to process (I), with free N and 0 atoms as the only conceivable products from energy transfer considerations.60 RECOMBINATION OF NO++e- Hansen has investigated other previous determinations of kl and fitted them to the expression : 4.8 x lo-* (kT)-* [l -exp (-0.27/kT)] ions-l cm3 s-l, where kT is in eV.This gives a room temperature dependence of T-3, changing to T-3 at high temperatures. This change is attributed to the participation of higher vibrational levels of the molecular ion. The temperature dependence of kl found from our work is in line with Hansen's conclusion. However, his correlation gives kl varying from 1.0 to 0.7 x ions-l cm3 s-1 at temperatures from 1820 to 2650 K, which is about a factor of 2 lower than the k l values determined here. The percentage temperature variations are about the same though.The measured kl values in fig. 5 have been taken together with the equilibrium constant of (I), as calculated from statistical mechanical considerations, to give I C - ~ , the rate coefficient for N+O --+ NO++e-. The results fit well to the expression k-l = 6.7 x 10-l2 exp (- 31 9OO/T) atoms-l cm3 s-l over the temperature range (1820 to 2650 K) of this work. The activation energy for this, the reverse of (I), 1.0 0.8 3 0;6 > .3 Y - 2 0;4 Oi2 I I I I 0 0; 2 0 : 4 0 ; 6 % volume NO in burner supplies FIG. 6.-Variation of kl with the amount of NO added to flame 5. is thus its endothermicity. The pre-exponential factor is roughly twice that given by Hansen at 2400 K and six times that from the work of kin and Teare at the same temperature.These authors give the pre-exponential factor varying as T4 and T-3, respectively, whereas our observations are more in line with it having no temperature dependence. The above expression for corresponds to a steric factor of 5 x All the results above have been arrived at on the basis of the reverse of (I) being unimportant in determining [NO+] in our flames. The rate coefficient, Ll, at 2500 K is 1.9 x lo-" cm3 atom-l s-l according to the above expression. It is thus possible to estimate the concentration of free nitrogen atoms necessary for the chemi- ionization rate k-,[N][O] to equal the recombination rate kl[NO+][e-1. Taking [NO+] = [e-] = lo1* ions ~ m - ~ , [O] = 1015 and kl = 1.5 x ions-l cm3 s-l requires CN] = 8 x 1014 atoms ~ r n - ~ , corresponding to a mole fraction of 3 x This is high for a flame without nitrogenous additives, because the natural [NO] in which reflects the inefficiency of chemi-ionization in this case.N.A . BURDETT AND A . N. HAYHURST 61 a C2H2/02/N2 flame at 2500 K is ’ -7 x 1015 molecules ~ r n - ~ and is very much less in H2 flames. However, there is evidence 2 o s 24 that when NO is added to a hydro- carbon-containing flame as above, a large fraction of it is converted in the reaction zone to substances such as HCN and possibly also a pool of N, NH, NH2 and NH3, with their concentrations linked by balanced reactions. For instance, it appears 24 that if NO is added to a flame of H2 + O2 + N2 with C2H2 also in the burner supplies, then significant fractions of the NO disappear in the reaction zone.In fact, the loss of NO is proportional to the amount of C2H2 present.24 Even so, the NO does reappear in the burnt gases with -97 % doing so after 1 ms for [C2H2] = 1 vol. %. This contrasts with the situation where NO is added to a H2/02/N2 flame without hydrocarbon present, when all the NO passes through the reaction zone unchanged and exists as such in the burnt gases.25 All this suggests that there might be situations when NO+ is formed by the reverse of (I), particularly when NO is added to C2H2 flames, thereby possibly liberating free N atoms in and close to the reaction zone. This has been tested by measuring kl in the C2H2 flame 5 with various amounts of NO added. On each occasion linear recombination plots were obtained and the results are plotted in fig.6 as kl (normalised on that for no added NO) against [NO] in the burner supplies. It is clear that kl is reduced on the addition of NO, which is in accord with N atoms being formed under these circumstances. In this case the equation governing [NO+] is The constancy of the observed effective recombination coefficient with time indicates that the ratio [r\sl[0]/[NO+J2 is only a weak function of time. These conclusions do not have any effect on the above determinations of k , in C2H2 flames, because NO was only added to the coolest ones and in amounts <O. 1 %, so that the k , values in table 2 are really for zero [NO]. As for H2 flames with the small amounts of additives used here (<0.7 vol. % of NO and <+ % of C2H2) the reappearance of NO from HCN and the pool of nitrogenous radicals N, NH, etc.is completed in the first 10 mm of the burnt gases.23 So, provided observations are made after this initial region and with small amounts of C2H2, as above, there is no reason to suspect the validity of the resulting kl. This work was financed by the S.R.C., whose support is gratefully acknowledged. A. Q. Eschenroeder and T. Chen, Amer. Inst. Aeronautics Astronautics J., 1966, 4, 2149. S. C. Lin and J. D. Teare, Phys. Fluids, 1963, 6,355. L. Thomas, J. Atmos. Terrestrial. Phys., 1976, 38, 61. C. F. Hansen, Phys. Fluid., 1968, 11, 904. J. A. Green and T. M. Sugden, 9th Int. Symp. Combustion (Academic Press, New York, 1963), p. 607 ; H. F. Calcote and D. E. Jensen, Adv. in Chemistry Ser., No. 58 (Amer.Chem. SOC., 1966), p. 291. I R. Hurle, T. M. Sugden and G. B. Nutt, 12th Int. Symp. Combustion (The Combustion Institute, Pittsburgh, 1969), p. 387. ’ N. A. Burdett and A. N. Hayhurst, 16th Int. Symp. Combustion (The Combustion Institute, Pittsburgh, 1977), p. 903. A. N. Hayhurst and D. B. Kittelson, Combustion and Flame, to be published. R. Kelly and P. J. Padley, Trans. Faraday Soc., 1970, 66, 1127. A. N. Hayhurst and N. R. Telford, J C S Faruday I, 1974,70, 1999. A. N. Hayhurst and N. R. TeIford, Combustion and Flame, 1977,28, 67. l 2 N. A. Burdett and A. N. Hayhurst, Proc. Roy. SOC. A , 1977, 355, 377. A. N. Hayhurst and D. B. Kittelson, Proc. Roy. Soc. A, 1974, 338, 155.62 RECOMBINATION OF NO++e- l4 A. N. Hayhurst, F. R. G. Mitchell and N. R. Telford, Int. J. Muss Spectr. Ion Phys , 1971, l5 A. N. Hayhurst, D. B. Kittelson and N. R. Telford, Combustion and Flame, 1977, 28, 123. l6 A. N. Hayhurst and N. R. Telford, Proc. Roy. SOC. A, 1971,322,483. l7 A. N. Hayhurst and D. B. Kittelson, Combustion and Flame, 1977,28,137. l8 Y. B. Zel'dovich, Acta Phys. Chim. U.S.S.R., 1946,21, 577. l9 A. N. Hayhurst and H.-A. G. McLean, Natlrre, 1974, 251, 303 ; A. N. Hayhurst and I. M. 2o C. Morley, Combustion and Flame, 1976, 27, 189. 21 H. C. Hershey, J. L. Zakin and R. Sirnha, Ind. and Eng. Chem. (Fundamentals), 1967, 6, 413. 22 A. Van Tiggelen, J. Peeters and C. Vinckier, 13th. Int. Symp. Combustion (The Combustion 23 F. C. Fehsenfeld, M. Mosesman and E. E. Ferguson, J. Chem. Phys., 1971,55,2115. 24 A. N. Hayhurst and I. M. Vince, unpublished work. 2 5 E. M. Bulewicz and T. M. Sugden, Proc. Roy. Soc. A , 1964, 277, 143. 7, 177. Vince, Nature, 1977, 266,524. Institute, Pittsburgh, 1971), p. 311. (PAPER 7/523)

ISSN:0300-9599    

DOI:10.1039/F19787400053

出版商:RSC    

年代:1978

数据来源: RSC

摘要:

Kinetics of Gas Phase Ion-Ion Recombination in NO+ +X- -+ NO+X for X being Chlorine, Bromine and Iodine BY NIGEL A. BURDETT AND ALLAN N. HAWURST* Department of Chemical Engineering and Fuel Technology, Sheffield University, Mappin Street, Sheffield, S1 3JD Received 25th March, 1977 The rate coefficient kl for the gas phase recombination of NO+ with halide ions X- in NO++X- -+ NO+X has been measured in flames of CzH2 + 02+N2 over the temperature range 2200 to 2650 K. Chlorine, bromine and iodine have been used as X. All kl values are in the range 0.8-2.1~ lo-* ion -l cm3 s-l, corresponding to cross-sections (d) of -lo-’’ mz. For each halogen, kl has a negative temperature cuefficient. Also at any one temperature, ki is largest for X being chlorine and smallest for iodine. In general, these measurements are in agreement with Olson’s “ absorbin8 sphere ” model for ion-ion recombination.Although the gas-phase recombination of NO+ with free electrons has been fairly extensively studied,lS the neutralization of NO+ with negative ions has not, apart from that with NOT at 300 K. In fact, ion-ion recombination has only been investigated experimentally on a handful of occasions, in spite of theoretical treat- ments of the topic having ab~unded.~ This work aims to measure the rate constant for NO+ recombining with halide ions in reaction (I) for X being chlorine, bromine and iodine. This has proved possible because in the burnt gases of a flame of C2H2+O2+N2 the dominant charged particles are H30+, NO+ and the free electron, with concentrations up to - loll ions ~ r n - ~ .In an acetylene flame, ions are first produced by CH+O + CHO++e- occurring in the reaction zone, although some possibly originate from CH + C2H2 + C3H; + e-. A primary ion rapidly reacts with neutrals present, such as NO and H20, giving NO+ and H30+, which are stable enough to persist into the burnt gases. Both these ions then recombine with free electrons in reactions (11) and (III) NO++X- + NO+X (1) NO++e- + N+O (11) H30++e- + H+H+OH (111) and in addition an equilibrium can be set up slowly’ between these two positive ions in reaction (IV) H30+ +NO + NO+ + H2O + H. (W When a halogen is added to such a flame, it exists as either free atoms X or as molecules of the hydrogen halide, with their concentrations being coupled by a rapid balance * of reaction (V) HX+H = X+H2.(V) 6364 ION-ION RECOMBINATION In addition, a minute fraction (< 1 in lo5) of the halogen atoms exist as X-. These are created in reaction (IV) which also becomes rapidly eq~ilibrated,~~ lo although this conclusion has been questioned.ll The effect of the presence of X- ions is to open up other routes for the disappearance of positive ions in reaction (I) and in its counterpart for H30+, i.e. which has already been studied.12 It has been shown that conditions can be created when reaction (11) is the dominant ionic reaction in the burnt gases of a flame. In this work the gradual addition of a halogen to the burner supplies brings process (I) into increasing prominence, thereby enabling its rate to be measured.HX+e- + X-+H, (VI) H30++X- -+ N,O+H+X, ( W EXPERIMENTAL The C2H2 flamcs, the burner and mass spectrometer have been described.l In this work small quantities (<1 vol. %) of a halogen were added to the unburnt gases of a flame by saturating a small part of the N2 supply with an organic halide. For chlorine either CHC13 or CC14 were used, for bromine n-C3H7Br and for iodine CH31 or C2H51. A knowledge of the vapour pressure of the volatile liquid, together with the gas flow being saturated, enables the rate of supply of halogen atoms to the flame to be deduced. These additives break up completely in the reaction zone giving mainly X atoms or HX molecules. The amounts of X- detected have been shown not to reflect accurately the concentrations of these ions at the point of sampling in the flame, because the equilibrium (VI) is fast enough to shift as the sampled gases cool whilst entering the spectr~rneter.~* lo This gives a loss of X- ions, in spite of the sampling time being -0.5ps.This of course reflects the rapidity of both steps in reaction WI). RESULTS In these C2H2 flames it was found that the degree of hydration of ions such as NO+ and H,O+ was much less than in H2 flames of a similar temperature. Typically, at 2200 K the ratios [H30+]/[M30~H20] and [NO+]/[NOfH,Q] are roughly 500 and 2000 in a C2H2 flame (depending on factors such as sampling hole size), but 3 and 40, respectively, in a H2 one. This is largely attributed to [H20] being smaller in C2Hz flames, but in addition C2H2 flames usually have thinner boundary layers around the sampling orifice, as well as shorter expansion times for the sample entering the first vacuum chamber of the mass spectrometer.The overall result is convenient, for it means that the difficulties of measuring [H,O+] when hydration is considerable are much diminished. In fact, in this work we have assumed that H30+ and NO+ are detected with identical sensitivities. One unexpected feature was the detection of positive halogen ions with iodine and bromine added, but not with chlorine. For bromine, Br+ and to a much less extent Brz were observed, but with iodine I+, I+H20, 12+ and 1; were found. In the latter case I+ is the most abundant, with a concentration exceeding that of 1: by at least a factor of 10. Both 12+ and I,’ usually had negligibly small concentrations.All these positive halogen ions appear to be formed in the reaction zone, in that their observed abundances decreased along the burnt gases. The positive ions of bromine always represented an insignificant portion of all the positive ions present, and in this sense could be ignored. However, with iodine, I+ was often the principal positively charged species in and close to the reaction zone. This is shown in fig. 1 for iodine in flame 5, (2380 K) where [H,O+] is always fairly small and the principal positive ion is I+ close to the reaction zone and NO+ after -7 mm downstream,N. A . BURDETT AND A . N. HAYHURST 65 It is convenient to deal first with the results for chlorine and bromine, which are not complicated by the presence of significant amounts of new positive ions.Fig. 2 shows profiles for [NO+] and [H,O+] along the axis of flame 6 (2200 K) with no NO or halogen added and with chlorine present. In the absence of additives, [NO+] peaks at - 12 mm from the reaction zone and subsequently decays downstream, being then larger than [H,O+]. The effect of C1 is to increase [NO+] and [H,Q+] and shift the maximum [NO+] downstream. Qualitatively, this must arise from recom- bination of NO+ and H,O+ with free electrons in reactions (11) and (111) being 5 10 15 20 axialldistance from reaction zonelmrn FIG. 1.-Concentration profiles for NO+, I+, H30+ and I- along the axis of flame 5 for 0.2 vol. % of iodine added. 0 10 20 30 LO distance from reaction zone/mm FIG. 2.-Experimental plots of [NO+] (triangles) and [H30+] (circles) along the axis of flame 6 ; A and 0 give ion concentrations in the absence of halogen and A and 0 are for chlorine added (0.34~01 %).1-366 ION-ION RECOMBINATION replaced by the slower processes (I) and (VII). Well downstream [NO+] % [H30+], so that H30+ can be ignored. Otherwise this condition can be achieved by the addition of small amounts of NO, with care being taken to avoid complications from the reverse of reaction (11) producing NO+. We first discuss observations made under conditions where NO+ is the major positive ion and the analysis is similar to that employed in a study l2 of reaction (VII). The decay equation is : -~ d"o+l = k,[NO+][X-] + k,[NO+][e-], dt where kl and k, are the recombination coefficients of reactions (I) and (11), respectively.Using the charge balance [NO+] = [e-]+[X-] and the equilibrium constant K6 of reaction (VI) to relate [e-] and [X-1, we obtain This suggests that the recombination plot of I/[NO+] against time has a gradient S, equal to the right hand side of eqn (I), i.e. Here 2 = K6[HX] J(K,[HX] + [HI) and represents the fraction of the negative charge carried by the halide ion. In general 2 is a function of axial distance along a flame S, = k,+(k,-k,)Z. 10 20 30 40 distance from reaction zone/mm FIG. 3.-Recombination plot of 1 /[NO+] against distance along flame 5 for chlorine concentrations in the unburnt gases as shown in vol. %. (or time), because it is affected by [HI being above its equilibrium value, which also can alter [HX] by a readjustment of reaction (V).In such a case the local ratio of the slopes of the recombination plots with and without halogen present is given by Some recombination plots for NO+ in flame 5 are shown in fig. 3, where the SJS, = 1 -(1 -kl Jk2) 2. (2)N . A. BURDETT AND A. N. HAYHURST 67 decrease in slope on the addition of chlorine is clear. In fact, in this case good straight lines are obtained for the region downstream of the maximum [NO+]. This linearity is fortuitous and is due to the insensitivity to distance of the function 2 in this particular case. In general curved recombination plots were obtained and their slopes S, obtained numerically after an initial smoothing.12* l4 These were then 0 I I I 1 I 0 0.2 0.4 0 . 6 0 . 8 1.0 z FIG. 4.-Experimental &/So for various 2 with chlorine added to flame 5 (0), and also bromine in flame 2 (A).In both cases data points are for sampling hole diameters in the range 0.10 to 0.17 mm. compared with the slope So for no halogen present and plotted against 2, according to eqn (2). Such a plot is shown in fig. 4 for bromine in flame 2 and chlorine in flame 5. In both cases it is evident that a straight line can be drawn through the data with an intercept of unity for 2 = 0. The slope of the best fit line gives k,/k2. It should be noted that fig. 4 has been drawn for a range of halogen concentrations and a variety of sampling hole sizes. The lack of any systematic variation with the latter confirms that there is no complication arising in this work by the observed [NO*] being falsified during sampling.The values of k , from the derived kl/kz and the k , measured previously are given in table 1. Whenever NO+ was not the sole dominant positive ion, as with iodine as additive, a different procedure for analysing the observations had to be adopted. In this case ions are disappearing by recombination in reactions (I)-(111) and (VII), as well as possibly in reactions (VIII) and (IX) I++e-+M + I+M (VIII) I++I- + I+I, (1x1 where M is any molecule acting as a chaperon. The overall decay equation is then In this equation [I-] is given by [e-][HX]K,/[H] and [HX] is obtained from the total amount of halogen added and K5, which along with K6 can be computed from normal68 ION-ION RECOMBINATION statistical mechanical procedures. [HI is known along each flame from measurements using the Sr+/SrOH+ technique.15 Charge balance gives [P+] = [NO+] + [H,O+] + [I+] = [e-]+[I-].In addition, it is known l3 that k , = 4.1 x that k7 can be taken l2 to be 1.2 x that k8 written in second-order form l 6 is 0.108 T-2 and k9 has been measured l6 as 9.0 x with all units being ions-l cm3 s-l. In this case, because k2 was measured in a previous paper,' k l is the only unknown quantity in eqn (3). TABLE MEASURED VALUES OF k l IN ion-' cm3 s-' flame temp/K lo7 kz lo8 kl(C1) lo8 kl(Br) lo8 kl(I) 1 2630 1.4 1.1 0.9 0.8 2 2650 1.4 1.3 1 .o 0.9 3 2590 1.5 1.4 1 . 1 1 .o 4 2490 1.6 1.5 1 .o 1 .o 5 2380 1.7 1.7 1.4 1.2 6 2200 1.9 2.1 1.6 1.4 Values of kl were thus arrived by substitution into eqn (3), the left hand side of which was obtained by numerically differentiating the concentration profiles of the three positive ions. In fact, as is clear from fig.1, NO+ did become the dominant positive ion at distances > 10 mm from the reaction zone, when recombination via processes (VIIT) and (IX) made little contribution to the right hand side of eqn (3). This approach of course depends on a calibration of the mass spectrometer, in contrast to the work with C1 and Br, where kl was obtained without a calibration by comparison with the well-established k Z . All the measured values of k l have been collected in table 1 together with those used for k2. The kl for C1 and Br are considered accurate to 70 %, whereas those for I are correct to within a factor of 2. This is because the dominant term on the right hand side of eqn (3) is that containing k l , so that errors in k3, k7, k8 and k9 are not of much consequence.DISCUSSION It is clear from fig. 5 that k l is greatest with Cl and smallest for I, as is the case l 2 for recombina- tion of the halide ions with H30+ in reaction (VII). In addition, kl depends on temperature in contrast with k7 and the indications of fig. 5 are that for all three halogens kl varies as T-2.5*2*2 . The magnitudes of k l are comparable with (marginally smaller than) those for k , indicating that their cross-sections are similar at nu2 - m2. The usual theoretical approach to bimolecular neutralization in A++B- -+ A+B involves a consideration of the pseudocrossings of the initial and final potential energy surfaces according to Landau-Zener theory l7 or some version of it.One such modification is due to Olson l8 and considers the recombination of ions, such as molecular ones, for which there are many pseudocrossings, because of the large number of electronic, vibrational and rotational states. This approach defines a critical distance R, between A+ and B-, such that there is unit probability of reaction for all separations < R,. The resulting recombination coefficient given by this " absorbing sphere model " is The measurements have been plotted in fig. 5 as log kl against log T. 1.1 .:(-J(1+&) 8nkTN . A . BURDETT AND A. N . HAYHURST 69 where p is the reduced mass of A+ and B-, k is Boltzmann’s constant and e is the electronic charge. R, is obtained from empirical correlations 9 of the dependence of the matrix elements on interparticle separation and is characterised by the reduced mass of the ions FIG.5.-Logarithmic plots of kl against T for the three halogens. Table 2 gives values of R,, as well as a comparison of the rate coefficients kl and k7 as computed from the absorbing sphere model (at 2000K) with those measured experimentally here and earlier. The agreement between theory and experiment is satisfactory, being within the error limits of both values, except possibly for iodine ions. The measured coefficients show a much greater variation from one halogen TABLE 2.-vALUES OF R, AND SOME EXPERIMENTAL AND THEORETICAL RECOMBINATION COEFFICIENTS FOR ION-ION NEUTRALISATION AT 2000 K IN UNITS OF lo-* ions-l cm3 s-I species experimental theoretical Rc/nm H30++ C1- 4 .1 3.4 1.67 H30++ Br- 2.7 3.2 1 . 7 6 HSO++I- 1 . 2 3.3 1.86 NO++ Cl- 2.7 3.0 1 . 6 9 NO++ Br- 2.0 2.7 1 . 7 6 NO++ I- 1 . 7 2.8 1.89 to another than do the computed ones. Also, recombination appears to be faster with H30+ than NO+ to a slightly greater extent than predicted. Finally, the theoretical approach outlined above gives a T-* dependence on temperature, since here e2 % R,kT. This compares with the To*o*2-o found l 2 for H30+ recombining with halide ions in reaction (VIII) and T-2*5*2.2 for NO+ here. Clearly, the accuracy of these measurements would have to be very significantly improved to check the predicted T-* dependence. Finally, we have measured 16* 2o the recombination coefficients for A++B- -+ A+B, for A being an alkali metal, Ga, In or TI, and B a halogen.The pair Na/I gives the largest coefficient of 3 x ions-l cm3 s-l in a flame at 2080 K, and the smallest measureable one was 1.5 x 10-l2 ion+ cm3 s-l for Rb/Br and Cs/I, both at 1820 K. Some pairs, particularly with Cs and Rb, have values too small to be measured. In general, it is clear that ion-ion recombination is characterised by the70 ION-ION RECOMBINATION nature of the " crossing " of the initial and final potential energy curves of the system, but broadly speaking the process is faster for molecular ions than atomic ones, because of the extremely large number of these pseudocrossings. This work was made possible by financial support from the S.R.C., which is gratefully acknowledged. N. A. Burdett and A.N. Hayhurst, J.C.S. Faraday I, 1978, 74, 53. C. F. Hansen, Phys. Fluid, 1968, 11, 904. B. H. Mahan and J. C . Person, J. Chem. Phys., 1964, 40, 392. M. S. W. Massey and K. B. Gilbody, Electronic and Ionic Impact Phenomena, Vol. 4, Recombi- nation and Fast Collisions of Heavy Particles (O.U.P., Oxford, 2nd edn, 1974). P. F. Knewstubb and T. M. Sugden, 7th Int. Symp. Combustion (Butterworths, London, 1959), p. 247; H. F. Calcote and D. E. Jensen, Adu. in Chemistry ser., No. 58 (Amer. Chem. SOC., 1966), p. 291 ; A. N. Hayhurst and D. B. Kittelson, Combustion and Flame, to be published. J. A. Green and T. M. Sugden, 9th Int. Symp. Combustion (Academic Press, New York, 1963), p. 607. N. A. Burdett and A. N. Hayhurst, 16th Int. Symp. Combustion (The Combustion Institute, Pittsburgh, 1977), p. 903. L. F. Phillips and T. M. Sugden, Canad. J. Chem., 1960,38, 1804. N. A. Burdett and A. N. Hayhurst, 15th Int. Symp. Combustion (The Combustion Institute, Pittsburgh, 1975), p. 979. H. F. Calcote, 15th Int. Symp. Combustion (The Combustion Institute, Pittsburgh, 1975), p. 990. lo N. A. Burdett and A. N. Hayhurst, Proc. Roy. SOC. A, 1977, 355, 377. l2 N. A. Burdett and A. N. Hayhurst, J.C.S. Faraday Z, 1976, 72, 245. l 3 A. N. Hayhurst and N. R. Telford, J.C.S. Faraday I, 1974, 70, 1999. l4 H. C. Hershey, J. L. Zakin and R. Simha, Zd. and Eng. Chem. (Fundamentals), 1967, 6, 413. l5 A. N. Hayhurst and D. B. Kittelson, Proc. Roy. Soc. A , 1974,338, 155. l6 N. A. Burdett and A. N. Hayhurst, unpublished work. l7 L. D. Landau, Phys. Zeitschr. Sowjetunion, 1932, 2, 46 ; C. Zener, Proc. Roy. SOC. A, 1932, l8 R. E. Olson, J. Chem. Phys., 1972,56, 2979. l 9 R. E. Olson, F. T. Smith and E. Bauer, Applied Optics, 1971, 10, 1848. 2o N. A. Burdett and A. N. Hayhurst, Chem. Phys. Letters, 1977, 48, 95. 137, 696. (PAPER 7/524)

ISSN:0300-9599    

DOI:10.1039/F19787400063

出版商:RSC    

年代:1978

数据来源: RSC

摘要:

’Li, 23Na and 9Be Nuclear Magnetic Resonance Investigations of the Influence of N-Substitution on the Solvation Interaction of Amides with Alkali and Alkaline Earth Metal Ions BY BERND M. RODE,* THOMAS PONTANI Innrain 52 a, A 6020 Innsbruck, Austria Institut fur Anorganische und Analytische Chemie der Universitat Innsbruck, AND GERNOT HECKMANN Institut fur Anorganische Chemie der Universitat Stuttgart, Pfaffenwaldring 55, D 7000 Stuttgart, Germany Received 25th March, 1977 ’Li, 9Be and 23Na chemical shifts of metal salt solutions in formamide and its mono- and di-N- substituted derivates have been investigated in order to obtain information about the influence of N-methylation and N-ethylation on the interaction of the amide group with alkali and alkaline earth metal ions. Concerning the interaction with Li+ and Na+ ions, methyl and ethyl substitution were found to have an opposite influence on the shifts, whereas in the case of BeZ+ ions all kinds of substitution shift the resonance signal towards higher field.Quantum chemical calculations with minimal Gaussian basis sets were employed in order to obtain some additional information about the background of the substituent effects and the exceptional line broadening observed for the metal ion solvates with diethylformamide. The results are discussed with respect to reported relations between metal resonance shifts and the donor abilities of the solvents. The interaction of amides, peptides and proteins with metal ions has interest for inorganic, theoretical and biological chemists and has been, therefore, the subject of numerous investigati0ns.l Considering the strongly differing solvating properties of various N-substituted amides,2 questions concerning the specificity of peptide binding sites for alkali and alkaline earth metal ions in biosystems and the affinity of such ions to certain parts of protein membrane layers, it seemed desirable to begin some systematic experimental and theoretical studies on the influence of substituents at the nitrogen atom of the peptide group on its ion binding properties.In the first part of these studies, presented here, this influence has been studied investigating the effect of methyl and ethyl groups at nitrogen on the amide’s ligand properties with respect to Li+, Na+ and Be2+ ions. As an experimental tool for these investigations we chose 7Li, 23Na and 9Be n.m.r.measurements, which reflect, by means of chemical shifts and line widths, the ligand induced changes in the electronic environment of the nuclei of the solvated metal ions. These experiments have been supplemented by ab initio calculations with minimal basis sets for the 1 : 1 complexes of the amides with the cations. EXPERIMENTAL METHOD It has been shown by several workers, that the alkali metal n.m.r. technique, particularly 23Na and 7Li n.m.r., is a very sensitive tool for investigation of the immediate chemical 7172 N.M.R. OF SOLVATION INTERACTION environment of alkali metal ions. It has been used extensively for studies on ion interactions with non-aqueous solvents as well as for determination of preferential ~olvation.~-~ Magnitude and direction of chemical shifts have been related to basic chemical properties like the basicity or donor abilities of the solvent^.^^ Using this technique we could expect, therefore, to obtain some reliable experimental information about the influence of N-substitution on the interaction of the amides (and the peptide group, respectively) with these ions. Only very little work has been done using 'Be n.m.r.' The reported data indicate, however, that the method should be as suitable for our investigations as 7Li- and 23Na n.m.r.spectroscopy. Thus we included the Be2+ ion in our investigations in order to obtain some general information about the principal differences between the singly charged alkali and the doubly charged alkaline earth metal ions in their interaction with amides.Theoretical calculations on ion complexes with dimethylformamide, by means of a mixed electrostatic- quantum chemical model,1° have indicated the existance of characteristic, different behaviour of the alkali and alkaline earth ions, respectively, in their influence on the ligand's electronic structure. Having measured the shifts for the metals complexed by the various substituted amides one can determine the influence of the substituent, regarding the values for the unsubstituted formamide as a reference for the other compounds. Since the differences are not expected to be too big, an accurate determination of chemical shifts was necessary. Determination of the magnetic susceptibilities of the solvents was, therefore, inevitable, since there are no data available in literature, except for formamide itself.For the solutions used in the experiments (and, of course, for the aqueous standard solutions) corrections to the susceptibility due to the salt influence were made using the tabulated values for these salts.ll An estimation of the accuracy in the determination of the chemical shifts, based on the line widths of the resonance lines for the nuclei, led to the values kO.2 Hz for Li, and +4 Hz for Na and Be. According to the results for anion and concentration influence on the chemical shift '1 l2 we chose the perchlorates of Lif and Na", and the sulphate of Be2+ for our measurements, which should guarantee the best conditions for the determination of shifts.N.M.R. MEASUREMENTS All spectra were recorded at 25°C with a HFX-90 n.m.r. spectrometer (BRUKER-Physik AG) with Fourier unit. 7Li spectra were recorded at 33.55 MHz, 23Na and 9Be spectra at 22.62 and 9.12 MHz, respectively. The magnetic field strength was adjusted correspondingly to these frequencies at 20.28,20.08 and 15.24 kG, respectively. The samples were measured in rotating 10 mm 4 tubes with 3 mm 4 reference capillaries. In the tables, a positive sign denotes a shift to higher field, a negative sign a shift to lower field strengths. For the Li measurements, no n.m.r. lock was necessary, since the use of the pulse Fourier technique with an acquisition time of 4.27 s allowed the field to drift at a value of +O.l Hz during the recording of one spectrum.The 23Na spectra were recorded with frequency sweep, the field being kept constant by a homolock to the reference signal. For the 'Be pulse Fourier spectra, an accumulation of 100 interferograms was necessary. During the total recording time of 42.5 s, a maximum field drift of 1 Hz could be maintained, so that the use of an n.m.r. lock could be avoided. As reference solutions, we used saturated aqueous solutions of reagent grade LiCl, NaCl and BeCl,. The relative methodical errors within these experimental conditions have been pointed out in the previous chapter. PREPARATION OF THE SAMPLES A N D SUSCEPTIBILITY MEASUREMENTS Anhydrous reagent grade salts, LiC104 (Alfa Ventron), NaC104 (Merck) and BeS04 (Fluka), were dried for 48 h at 150°C before use. The amides (Fluka) were dried over a molecular sieve (4 A).0.5 mol dm-3 solutions of the salts in the amides were prepared under nitrogen atmosphere. The susceptibility of the amides was determined after the Gouy method l 1 with a 3-MB-6B . M. RODE, T . PONTANI AND G. HECKMANN 73 (BRUKER Physik AG) magnetic balance, using n-butylbenzoate as reference. Taking into account the salt contributions to the diamagnetic susceptibility," the corrections to the chemical shifts for the solutions were performed according to the formula of Zimmermann and Forster.13 QUANTUM CHEMICAL CALCULATIONS In order to facilitate the discussion of the results, it seemed desirable to have some theoretical information about ligands and solvated cations. For this purpose, we performed ab initio calculations with minimal I4 GLO basis sets for these systems. The basis set has already been successfully used in several works on ion influence on amides and could, therefore, be expected to give reliable information at a qualitative level.For the amides, we maintained the experimental geometry, the cation positions were optimized with respect to total energy. The calculations were performed in part on the CDC 3300 computer of the University of Innsbruck and in part on the CDC Cyber 74 computer of the technical University of Vienna, using the program MOLPRO by Meyer and Pulay. RESULTS AND DISCUSSION SUSCEPTIBILITY MEASUREMENTS OF THE AMIDES I n table 1 we have listed the volume susceptibilities of the amides, which were investigated during this work. These values show that &substitution may signifi- cantly alter the magnetic behaviour of amides and that correction of the chemical shifts was actually necessary for a reliable interpretation of the n.m.r.spectra. The calculated l1 susceptibilities of the reference solutions are also listed in table I. TABLE 1 .-VOLUME-SUSCEPTIBILITIES OF AMIDES AND STANDARD SOLUTIONS formamide (FA) -0.550~ low6 LiCl a : - 1.087~ N-methylformamide (NMF) - 0 . 5 1 3 x NaCl a : - 1.000~ N, N-dimethylformamide (DMF) BeCI, a : - 0.889 x N, N-diethylformamide (DEF) - 0 . 5 4 4 x - 0.668 x N-ethylformamide (NEF) - 0 . 6 4 2 x a Saturated aqueous solutions N.M.R. MEASUREMENTS In table 2, the non-corrected chemical shifts for Li, Na and Be in the five amides are presented and compared with the susceptibility corrected shifts.TABLE 2.-cHEMICAL SHIFTS, RELATED TO STANDARDS (a) UNCORRECTED (6) BULK SUSCEPTIBILITY CORRECTED (IN HZ) ion a b a b a b a b a b FA NMF DMF NEF DEF Lif 1 1 . 6 -24.9 5.0 - 3 4 . 1 7.0 -30.0 5.1 - 2 4 . 9 5.5 -22.5 Na+ 118 98 1 2 6 1 0 4 126 105 1 1 2 96 104 89 Be2+ -7 - 1 3 -2 -9 8 2 -4 - 8 4 0 Since the influence of the ligand molecule on the electronic environment of the cations can be assumed to increase approximately linearly with the number of ligands in the first coordination sphere, we have to take into account the average coordination numbers n in this sphere for the evaluation of the " specific '' substituent influence. These average coordination numbers iz were obtained from recent vapour pressure measurements and are listed in table 3, together with the chemical shifts, JFA174 N.M.R.OF SOLVATION INTERACTION related now to formarnide as the unsubstituted “standard” amide. The final values, which allow us to estimate the substitution effect on the complexation of the cation by the amide’s carbonyl group, are collected in table 3, namely the coordination number corrected shifts, a,, related to the coordination number of the Li, Na and Be amide solutions, and the line widths Av of the n.m.r. signals. One can first observe the opposite direction of the substituent induced shifts d,, for Li and Na, respectively. Methyl groups shift the Li signal to lower field strengths, ethyl groups to higher field. The Na signals show the opposite behaviour. The different electronic structure of these ions may provide a reason for this opposite effect.TABLE 3.-CHEMICAL SHIFTS &A, RELATED TO FORMAMIDE, AVERAGE COORDINATION NUMBERS, n, COORDINATION NUMBER CORRECTED SHIFTS a,, AND LINE WIDTHS Av (IN Hz) ion FA NMF DMF NEF DEF - 9.2 4.9 5.6 - 8.1 8 .O 8.5 6 4.1 4.8 +5 45 60 4 (6) (6) +4 30 30 - - - - - - - 5.1 2 . 4 - 10.4 7.0 7 2.2 + 13 50 15 4.0 + 23 24 0 4.8 0 9.5 -2 4.0 -2 150 5 (6) +5 30 + 2.4 3 .O + 3.9 19.0 -9 2.0 - 19 130 13 (4) a + 20 60 a Values in parentheses are estimated coordination numbers Whereas lithium with its ls2 electron configuration should be influenced mainly by changes in the diamagnetic shielding, a dominating paramagnetic shielding term is expected in the case of sodium. This is confirmed by the results of 23Na and 7Li shift measurements in various nonaqueous solvents with strongly differing donor abilities,15~ l6 where Li and Na also show opposite behaviour with respect to their n.m.r. absorption frequencies.It is diEcult to find a reasonable explanation, however, for the behaviour of CH,-groups at nitrogen as “ electron acceptors ” for Li+ and C2H,-groups as “ donors ” without further information, as, for example, could be provided by quantum chemical calculations. For Be, we found a shielding effect for all kinds of substitution investigated ; disubstitution increases the shielding effect strongly in the case of methyl as well as ethyl groups. Obviously, a character- istic difference exists between the substitution effects with respect to the interaction with either mono- or di-valent ions.A second interesting fact, observed in the results of our n.m.r. experiment is the strong line broadening of the resonance signals of all ions upon diethylation of the amide’s nitrogen, indicating that this kind of substitution causes a strong non- symmetry in the electronic environment of the nucleus. This effect will be discussed in more detail in the following section. QUANTUM CHEMICAL CALCULATIONS Calculations were carried out for the five amides and most of their 1 : 1 complexes with Li+, Be2+ and Na+. For comparison with the n.m.r. results, special attention was paid to the population analysis, which was performed after the MullikenB . M. RODE, T . PONTANI AND G . HECKMANN 75 procedure, and to the orbital densities at the metal nucleus, which can both represent a helpful tool in the discussion of chemical shifts.Owing to the use of a rather unsophisticated wave function, i.e. the minimal basis sets, one cannot formulate more than a qualitative discussion on the basis of these calculations. For this reason, an analysis of the total electron density function of the systems was not expected to supply more information than the atomic net charges and orbital densities at the nucleus to a discussion of chemical shifts. On the other hand, the larger systems did not allow an extension of the basis set without reaching unreasonable computing times. Semi-empirical procedures are not suitable for the ion-amide complexes for reasons of method,lP l4 and because the description of the metal ion in a valence basis set only cannot lead to reliable information about the electronic environment of the metal nucleus.TABLE 4.-cALCULATED ATOMIC NET CHARGES OF LIGAND ATOMS AND METAL IONS, 4, AND ORBITAL DENSITIES AT THE METAL NUCLEI, Q system FA/Li NMF/Li DMF/Li NEF/Li DEF/Li FA/Be NMF/Be DMF/Be NEF/Be DEF/Be FA/Na NMF/Na DMF/Na NEF/Na FA NMF DMF NEF DEF 4c 0.553 0.594 0.618 0.579 0.597 0.706 0.727 0.748 0.708 0.723 0.529 0.571 0.591 0.551 0.436 0.478 0.505 0.465 0.490 4 0 - 0.528 - 0.535 - 0.541 - 0.526 -0.517 - 0.985 -0.951 - 0.957 - 0.956 - 0.922 - 0.464 - 0.470 - 0.472 - 0.462 - 0.250 -0.251 - 0.257 - 0.247 - 0.246 4-n + - 0.012 - 0.012 - 0.012 -0.012 - 0.012 - 0.003 - 0.003 - 0.003 - 0.003 - 0.003 - 0.027 - 0.028 - 0.028 - 0.028 - - - - - Q 2.765 24 2.765 45 2.765 49 2.765 41 2.765 74 9.487 71 9.476 76 9.476 88 9.476 80 9.475 97 248.717 23 248.717 81 248.712 46 248.712 25 - - - - - In table 4, the net atomic charges of the ligand’s carbonyl group qc, qo and the metal ions’ qMe are presented, together with the calculated orbital density Q at the metal nucleus.In the last part of this paper we will try to analyse the experimental data with the aid of results obtained in the calculations. DISCUSSION OF EXPERIMENTAL AND THEORETICAL RESULTS FOR THE INFLUENCE OF N-SUBSTITUTION O N CATION-AMIDE BINDING Some critical considerations about the significance of the results seem useful at this point. We have given an outline of the accuracy of the n.m.r. experiments at the beginning of the Discussion. Comparing the shifts with methodical accuracy we can expect a correct description of the “ trends” within the investigated series;76 N .M . R . OF SOLVATION INTERACTION the numbers do not seem reliable, however, for an estimation of the influence in a quantitative sense. The necessary restriction of the quantum chemical calculations to strongly simplified models for the solvated ions, in our work on the 1 : I models, leads to some principal limitations in their applicability. In the case of the amides, however, it has been shown by a comparison of experimental ion influence on the amide’s rotational barrier and the calculated results for the 1 : 1 complexes and complexes of higher order,l* lo that the former represent a quite reliable description of the solvated ion. We could expect, therefore, an acceptable description of the substitu- tion influence, again in a qualitative sense only.Further, the average coordination numbers of the metal ions under the experimental conditions of the n.m.r. measure- ments are, according to vapour pressure measurements,2 very low (1.1-2.5), so that a good part of the metal ions actually should be present in the form of 1 : 1 complexes. The most problematic step in the comparison of experiment and calculations seems to be, therefore, the relation of calculated quantities to chemical shifts. Whereas such a relation is still quite easy to construct in the case of proton shifts, the composition of the metal shifts is highly complicated and a reliable calculation has to involve, therefore, a detailed analysis of the wavefunction, which did not seem useful for our rather unsophisticated basis set.What could be done, therefore, was to attempt a more or less “empirical” comparison with calculated quantities, which could be expected to be related to the electronic environment and thus to the shifts of the metal nuclei. Such quantities were the orbital densities at the coordination site. Considering the results of the calculations and the experimental data, we find immediately, that the orbital densities do not account at all for the observed effects. A reason for this may be that this quantity should reflect only the diamagnetic shielding component, which in the case of the metals is not as important as for hydrogen. The electron density at the cation was constant over the whole series of amides and, hence, also did not give any clues to the observed experimental effects.The electron density at the coordination site, i.e. at the oxygen atom, however, seems to be related to the shifts observed in the n.m.r. measurements. For the free iigands, methyl substitution leads to an increase in the electron density of the oxygen atom, whereas ethyl substituents have the opposite effect (cf. table 4). These effects are basically maintained in the complexes of Li-t- and Naf, but not in the Be2+- complexes, where the density is lowered. The parallel nature of this behaviour and the behaviour of the chemical shifts is obvious, taking into account, that the resonance frequencies of Li and Be should undergo a shift opposite to that of Na, upon the same change in the electronic en~ironment.~~ The correlation, that electron density decrease at the coordination site in the complex leads to a shielding effect on Li and Be nuclei and to a deshielding of the Na nucleus and vice versa, seems to be in some “ agreement ” with another empirical correlation between Na shifts and the donor numbers of various solvents,15* I 6 namely, that as the donor ability of the ligand becomes better, so the Na resonance frequencies shift downfield.Such a correlation could not be observed in the Ei, probably because of the dominance of other influences (e.g. ring currents) in the composition of the shifts.12 In the case of our very similar ligands, these influences should be almost constant, thereby enabling the observation of a correlation analogous to sodium.A satisfactory interpretation of the correlations between chemical shifts and donor site electron density on the one hand, and donor numbers on the other hand has yet to be formulated. The amount of electron density calculated for the metalB . M. RODE, T . PONTANI AND G . HECKMANN 77 binding site could influence the metal shift as a pure " neighbouring-atom-effect ", but it might have also some influence on electron transfer processes to unoccupied metal orbitals, which are supposed to contribute to the chemical shifts of these nuclei as well.7 The donor number again is a measure of the ability of the ligand to interact with Lewis acids, and it is reasonable, therefore, to expect that the electron density of the binding site is related to this macroscopic quantity.The investigation of ligands with minor structural differences, as performed here, reflect these correla- tions more clearly than the studies employing very different ligands, but they also confirm some of the tentative conclusions drawn from such investigations.'~ 16* l7 Summarizing our conclusions on the relation between metal n.m.r. shifts, donor qualities of the ligands (in this case influenced by N-substitution) and calculated quantum chemical data, we suggest that : the better the donor quality of the ligaiid, the lower is the gross population of the binding site in the complex. This lowering of electron density leads to shielding effects for Li and Be and to deshielding for Na nuclei. The donor quality of a ligand also depends on the respective acceptor, as can be seen in our examples of the values for Li and Na compared with those for Be.TABLE 5.-cOMPONENTS OF THE DIPOLE MOMENT VECTOR (IN ATOMIC UNITS) AND ANGLES MOLECULES ARE c O/O N : -2.583/0 0 : 1.299/- 1.957 FA NMF DMF NEF DEF BETWEEN DIPOLE VECTOR AND C=O BOND AXIS. THE CARTESIAN COORDINATES OF THE LIGAND x -0.863 -0.869 -0.841 -0.790 -0.573 Y 0.522 0.584 0.505 0.502 0.576 u 154.8 155.8 154.6 156.0 176.6 For the latter, both methyl and ethyl substitution iiiiproves the donor quality of the arnide, whereas for Li and Na ethyl substitution leads to better donating abilities compared with the unsubstituted amide, and methyl substitution reduces the donor quality. These conclusions only form a more or less empirical " description " of the observed relations between macroscopic and molecular quantities, and a satis- factory explanation of these relations can be expected only from much more sophisticated quantum chemical calculations, which cannot be performed at present for these large systems.A further problem was, why the n.m.r. line widths are broadened in the solvate complexes of diethylformamide of all the ions being investigated. Considering the calculated dipole moments and their components, for all of the ligand molecules, one observation could provide a possible explanation for this phenomenon (cf. table 5). The dipole vectors of all amides show approximately the same direction, except DEF, where it lies almost exactly in the C=O bond axis, which points to the metal binding site.This coincidence should allow higher polarization of the core electrons at the metal ion and hence lead to a stronger non-symmetry in its electronic environ- ment. Such non-unsymmetry, however, will necessarily lead to greater line widths. The very low coordination numbers of the metal ions in this amide also give some significance to this result for the solution, although the calculation describes an isolated 1 : 1 complex. A second factor influencing the line widths, is the exchange time for ligands between complex and bulk solvent. The viscosities of the arnides do not indicate, however, any specific difference in this sense. A satisfactory solution to this problem can be expected, therefore, only from detailed studies of the exchange kinetics, which78 N.M.R.OF SOLVATION INTERACTION could also give an explanation for the line broadening in the Na+/NEF complexes, where the calculated data do not give any information. Financial support by the " Fonds zur Forderung der Wissenschaftlichen Fors- chung" is gratefully acknowledged. Thanks are due to the computer centres of the University of Innsbruck and the Technical University of Vienna for computing time. B. M. Rode, in Metal-Ligcind Interactions in Organic and Biochemistry, The Jerusalem Symposia on Quantum Chemistry and Biochemistry (D. Reidel, Dordrecht, Holland, 1976), and references therein. Th. Pontani, Thesis (University of Innsbruck, 1976). D. Noble, in Biological Membranes (Oxford Univ. Press, 1975). M. Herlem and A. I. Popov, J. Amer. Chem. Soc., 1972, 94, 1431. R. H. Erlich, M. S . Greenberg and A. I. Popov, Spectrochim. Acta, 1973, 29A, 543. J. F. Hinton and R. E. Briggs, J. Magnetic Resonance, 1975, 19, 393. ' E. G. Bloor and R. G. Kidd, Canad. J. Chem., 1968,46,3425. * R. H. Erlich and A. I. Popov, J. Amer. Chem. SOC.. 1971,93,5620. F. W. Wherli, J. Magnetic Resonance, 1976, 23, 181 and references therein. P. W. Solwood, Magnetochemistry (Interscience, N.T /London, 2nd edn, 1956). l o B. M. Rode and R. Fussenegger, Mh. Chemie, 1977, 108, 703. l 2 A. I. Popov, Pure Appl. Chem., 1975, 41, 3. l3 I. R. Zimmermann and M. R. Forster, J. Phys. Chem., 1957, 61, 282. l4 B. M. Rode, Mh. Chemie, 1975,106,339. l6 Y . M. Cahen, C. A. Heh, P. R. Handy, E. T. Roach and A. I. Popov, J. Phys. Chern., 1975, l7 A. Saika and C . P. Slichter, J. Chem. Phys., 1954, 22, 26. R. H. Erlich, E. Roach and A. I. Popov, J. Amer. Chem. SOC , 1970,92,4989. 79, 80. (PAPER 7/525)

ISSN:0300-9599    

DOI:10.1039/F19787400071

出版商:RSC    

年代:1978

数据来源: RSC

摘要:

Adsorption of Butane-l,4-diol at the Hg-Aqueous Solution Interface Transition with Polarization between Two Ideal Adsorption Modelst BY FERNANDO PULIDORI, GIANNA BORGHESANI AND RODOLFO PEDRIALI Chemical Institute, Instrumental Chemical Analysis, The University, Ferrara, Italy AND ACHILLE DE BATTISTI AND SERGIO TRASATTI* Laboratory of Electrochemistry, The University, Via Venezian 21, 20133 Milano, Italy Received 2nd May, 1977 The adsorption of butane-1,4-diol on a polarized Hg electrode from both NaF and Na2S04 solutions has been studied by means of electrocapillary and capacity curves. Analysis has been carried out both at constant charge and at constant potential. Irrespective of the choice of the electrical variable, adsorption has been found to conform to congruent Langmuir isotherms on the negative side of the adsorption maximum, and to non-congruent isotherms on the other side.Results suggest that molecules adsorb flat on the surface. Non congruence may be described in terms of a saturation coverage linearly decreasing with electric field. The inner layer capacity at constant amount adsorbed has been determined up to saturation coverage over a wide range of electric field. Results are discussed in terms of a polarization-dependent adsorbate-solvent interaction on the surface. A detailed molecular model of the adsorption layer is suggested. Available data in the literature indicate that organic molecules adsorb with congruence 3-5 of isotherms either with respect to both charge and potential, or with respect to neither of the two electrical variables.Whereas the latter result is under- standable, it has been suggested 5* that the former is electrically unreasonable. Nevertheless, accurate experimental results '-lo suggest that it may in fact be possible. Damaskin,ll following up his early suggestion^,^* l2 has pointed out that simultaneous congruence is as a rule exhibited by substances with relatively high values of C1, the capacity at saturation coverage. The intrinsically low adsorbing power of such substances does not permit experimental data to be collected at very high coverages. Non congruence may thus be only apparent. It follows that the rationale behind simultaneous congruence with respect to both and E can only be discovered by improving the accuracy in collecting experimental data and by extending observations up to coverages close to saturation.Butane-l,4diol (BD) has been chosen because diols belong to the group of substances expected 2* l o p l3 to adsorb flat on the surface with apparent simultaneous congruence with respect to both electrical variables. Actually, the adsorption of this compound has already been investigated by Garnish et all0* l4 However, they restricted their analysis to concentrations ranging from 0 to 0.23 mol dm-3. Thus t Presented at the XI National Congress of the Italian Association of Physical Chemistry, S. Margherita Ligure, 9-11 December 1976. 7980 A D S ORP TI 0 N A T Hg-S 0 L U TI 0 N I N T ER FA C E the coverage was never above 0.7, which is probably too low to evidence non congruence, in the light of Damaskin’s arguments.’ ’ Furthermore, their data were derived only from electrocapillary curves, which are now known lP lS* l6 to give inaccurate results at positive rational potentials. EXPERIMENTAL Electrocapillary curves were determined for 3 1 concentrations, and capacity curves for 11 concentrations, of BD between 0.001 and 1 mol dm-3 in aqueous solutions containing 0.25 mol dm-3 NaF. Electrocapillary curves were also made for 9 concentrations of BD in 0.1 mol dm-3 Na2S04 aqueous solutions. This was done to investigate whether such a substitution of the supporting electrolyte, which improves the accuracy and reproducibility of electrocapillary data, is of any assistance in the diagnosis of the adsorption mechanism owing to the weak specific adsorption of sulphate i0ns.l’ Equipment and experimental procedure, including the account taken of capillary wear effects ** l8 in surface tension measurements have been described previously.7* l3 Hg was purified using standard procedures.BD was purified by four recrystallizations from the melt followed by double distillation in vacuu in the presence of anhydrous Na2S04. Solutions were prepared by weighing the desired amount of BD then adding the electrolyte and triply distilled water. Molar fractions (x) were calculated by assuming the density to be equal to 1 and independent of BD content. The maximum concentration investigated corresponds to about 0.02 molar fraction. This is sufficiently small for the solvent mixture to be assumed to follow Henry’s law.19-21 Deviations of the activity coefficient ofthe organic substance from unity can only affect the absolute value of AGZd, not the curvature of the (surface pressure, log x) curve.The maximum concentration is indeed so small that the medium effect on the activity of the supporting electrolyte is probably negligible.22* 23 The analysis was carried out at constant concentration of the supporting electrolyte. RESULTS Tables 1 and 2 summarize all relevant data for the solutions used in this work. Comparison of electrocapillary curves with twice integrated capacity curves showed that the calculated interfacial tension deviated from the experimental curve at both positive and negative rational potentials. Experiments with samples of different purity showed that the cathodic effect depended on the extent of purification. Small traces of impurities capable of depressing the negative desorption peak were also observed 8 * 2 4 3 2 5 with other substances.Electrocapillary curves on the other hand were apparently unaffected by the impurity content. Extensive and careful purifica- tions could not eliminate the effect completely. However, since in capacity curves there is no pronounced desorption peak at positive rational potentials, it is thought that discrepancies in that region are those usually observed and attributable to contact angle effects.15* l6 For the above reasons the analysis of data was carried out by relying only on electrocapillary curves at negative rational potentials, and on both sets of data at positive rational potentials.Procedures for the treatment of data were the same as those described in detail in previous paper^.^'^. 13# 26 Fig. 1 shows the zero charge potential shift upon adsorption of BD. As usually ob~erved,~-~* 26 data from electrocapillary curves in NaF lie 10 to 15 mV more negative than those found with the streaming electrode. This is due to some depression of the positive branch of the electrocapillasy curve.” l6 With Na,SO, the latter effect is less serious and the two sets of data are closer to one another. The shape of the dependence of AE, = on x,,, may give some qualitative indication of the nature of the isotherm. Substances obeying a Frumkin isotherm with particle- particle attraction have been found * * 9* 26 to exhibit on such plots the typical 27PULIDORI, BORGHESANI, PEDRIALI, DE BATTISTI AND TRASATTL 81 TABLE 1 .-DATA FOR BUTANE-1 ,q-DIOL SOLUTIONS USED IN THIS WORK. SUPPORTNG ELECTRO- 0 0.001 0.006 0.010 0.013 0.0165 0.02 0.022 0.028 0.032 0.038 0.048 0.06 0.07 0.08 0.09 0.1134 0.120 0.140 0.143 0.170 0.175 0.201 0.24 0.27 0.305 0.38 0.420 0.500 0.650 0.802 1 .Ooo 0 0.017 97 0.1078 0.1798 0.2338 0.2968 0.3598 0.3959 0.5040 0.5762 0.6845 0.8653 1.083 1.264 1.446 1.627 2.054 2.175 2.541 2.596 3.092 3.184 3.664 4.387 4.947 5.602 7.01 8 7.780 9.317 12.25 15.29 19.36 0.4300 - - - - - - - - - - - - - - - 0.3850 - - 0.3770 - - 0.3600 0.3430 0.3316 0.3410 0.3234 0.3300 0.3134 0.3180 0.3100 - 23.45 - - - - - - - - - - - - - - I 17.92 - - 16.96 - - 16.38 16.47 15.53 14.30 15.38 14.04 14.60 12.64 12.72 - 426.7 425.5 425.8 425.9 425.5 425.3 425.5 424.3 424.2 423.7 423.5 423.1 422.5 422.4 419.3 421.5 419.S 420.1 417.0 419.0 417.2 417.4 416.7 415.1 41 5.0 413.4 413.3 41 1.2 410.2 408.2 406.5 403.7 0.4439 0.4457 0.4401 0.4428 0.4368 0.4281 0.4308 0.4245 0.4325 0.4253 0.4216 0.41 35 0.4080 0.4120 0.4060 0.4041 0.41 30 0.391 1 0.3304 0.3857 0.3579 0.3798 0.391 9 0.3785 0.3 674 0.3689 0.3544 0.3573 0.3543 0.3575 0.3453 0.3333 S-shaped pattern.Fig. 1 suggests that BD may obey either a Langmuir isotherm or a Frumkin isotherm with particle-particle repulsion. Plots of surface pressure against CT or E showed that the adsorption maximum is probably concentration dependent. A more sensitive approach is the derivation of TABLE 2.-DATA FOR BUTANE-1,4-DIOL SOLUTIONS USED IN THIS WORK.SUPPORTING ELECTRO- LYTE, Na2S04 0.1 rnol dm-3 0 0.006 0.02 0.05 0.09 0.14 0.17 0.305 0.5 0.8 427.0 426.2 425.4 423.1 421.5 419.7 417.8 414.1 410.6 407.0 0.4383 0.4325 0.4290 0.41 56 0.3904 0.3762 0.3584 0.3561 0.3319 0.320682 A D S ORP T I 0 N A T Hg-SO L U T I 0 N INTERFACE omax and Emax from the coordinates of the intersection point of charge against potential curves.2* l 2 Fig. 2 shows the concentration dependence of omax. Its value tends to about -3.7 to -3.8 pC cm-2 for 8 -+ 1, whereas for 8 -+ 0, to a first approximation, amax was taken as - 3 pC cm-2. This value was successively refined to -2.8 pC cm-2 on the basis of additional data as described below. Accordingly, the value of Emax was found to shift from -0.56 V at low coverage to about -0.59 V - 5.0 7 -4.0- $ i3 f -2.0- x - 1.0- t - *-:- - -9- - -*- - Q-.-- -O- ---? -3.0*3* 0 1 I 1 0.2 0 .4 0.6 0.E BD molar fraction, x x lo2 FIG. 1 .-Zero charge potential shift of a Hg electrode upon adsorption of BD from aqueous solutions of different electrolytes. (0, A) 0.25 mol dm3 NaF, electrocapillary maximum ; (0) 0.25 rnol dm-3 NaF, streaming electrode ; ( x ) 0.1 mol dm-3 Na2S04, electrocapillary maximum. at surface saturation. Around the adsorption maximum isotherms are congruent with respect to neither of the electrical variables. Constancy in omax or Emax is a necessary even though not sufficient condition for congruen~e.~~ Congruence was tested to a first approximation by superimposition of surface pressure against log x plots.2* Congruence was found reasonably to be good at each charge and potential.However, preliminary calculations on the assumption of 3 FIG. 2.-Concentration dependence of the charge of maximum adsorption of BD on a Hg electrode. Base solution : (0) 0.25 rnol dm-3 NaF ; (A) 0.1 rnol dm-3 Na2S04.PULIDORI, BORGHESANI, PEDRIALI, DE BATTISTI A N D TRASATTI 83 coverage, 0 FIG. 13.-Change in inner layer potential drop at a Hg-aqueous solution interface with coverage with adsorbed BD. Base solution : (0) 0.25 mol dm-3 NaF, capacity data ; ( x ) 0.25 mol dm-3 NaF, electrocapillary data ; (A) 0.1 mol dm-3 Na2S04, electrocapillary data. Difference between linear and non linear behaviour is emphasized. congruence with respect to charge showed that the potential shift at charges between - 2 and + 2 undoubtedly exhibited some non-linear variation with coverage.This is shown in fig. 3. This was thought to indicate '* lo non congruence at these charges I I 1 1 I I I I I t I I 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 0 BD molar fraction, x x 10' (6) constant potential. FIG. 4.-Test of the Langmuir isotherm for BD adsorption on a Hg electrode. (a) Constant charge;84 ADSORPTION AT Ha- 0 SOLUTION INTERFACE and possible congruence at more negative charges where plots were strictly linear up to 0.9 coverage. The nature of the isotherm was investigated by determining surface excesses by differentiation of surface pressure against log x plots.28 In the range of congruence, a Langmuir isotherm is followed with rs = 4.1 mol cm-’. Plots of x l r against x, as a test for this isotherm,’ showed a strictly linear behaviour (fig.4). The value found for rs corresponds to a covered area of about 0.41 nm2 per molecule. This value is in good agreement with the area projected by a molecule of BD lying flat on the surface ’’ and is also consistent with the value of 0.31 nm2 found for ethylene Acid was derived by calculating the theoretical surface pressure curve with rs = 4.1 x rnol cm-2 and fitting to the experimental points at the various charges. Results showed that at charges more positive than -3 ,uC the surface pressure curves flatten down slightly. This could be recognized in this work only because results extend to high values of @. At low and intermediate values of <D the coiidition of congruence may be taken as apparently met and this explains the findings of’ Dutkiewicz et a!.,1° who ineasured @ up to 1.2 pJ cm-2 whereas here CP values up to 2.4 pJ cm-2 at the point of maximum adsorption were measured.each additional CH2 group contributing N 0.05 nm2. (TI& cm-2 FIG. 5.-Charge variation of the surface saturation concentration in the Langmuir isotherm for adsorption of BD on a Hg electrode. Flattening of the surface pressure curve may indicate either particle-particle repulsion, or decrease in I-‘,. Tests of the Frumkin isotherm at +2 pC cm-2 with rs = 4.1 x 10-lo actually suggested a positive value for the interaction parameter which, according to the isotherm in the form : corresponds to particle-particle repulsion. The tests of the Langmuir isotherm shown in fig.4 suggest that this isotherm is probably also better followed at positive changes with rs decreasing with charge becoming more positive. Fig. 5 shows that I‘s decreases linearly with charge, as observed *. 26 with other organic substances. Fig. 6 shows the charge dependence of AG& as found by superimposing surface pressure curves at different 0 and E to those at cmax and Em,,, respectively. The same features as those reported by Dutkiewicz et aL1* can be recognized. At constant Ethere is no criterion by which one might assume non congruence at positive rational potentials. However, whereas for potentials negative to -0.56 V a strictlyPULIDORI, BORGHESANI, PEDRIALI, DE BATTISTI AND TRASATTI 85 0 I 2 3 4 (E- ~max)21V2 FIG. 6.-Change in standard free energy of adsorption of BD on a Hg electrode (a) at constant charge and (b) at constant potential.(0) Charges more negative than - 4 pC cm-2 ; potentials more positive (A) and more negative (0) than -0.55 V. ( . . . ) According to Dutkiewicz et a1.lo (- - -) Calculated according to eqn (6a) (see text). quadratic potential dependence 2* 30 of log p has been found, at more positive potentials the relationship is more complex and, in any case, the points lie above the straight line. This confirms the findings of Dutkiewicz et aPO Values of AGtd at charges more positive than -4 pC cm-2 were derived by fitting surface pressure curves calculated with the given value of rs to the experimental t I 1 I t I I I lo 5 0 -5 -10 -15 u/pC cm-2 FIG. 7.-Charge dependence of the standard free energy of BD adsorption on a Hg electrode.(- - -) According to the same quadratic dependence as at negative charges. (0) Experimental points.86 AD SORP TI 0 N A T Hg-S 0 LU T I 0 N I NTER F A CE points. Fig. 7 shows that AG,Od decreases quadratically with charge for CT more negative than -4, whereas on the other side it decreases more slowly. Assuming strict congruence with respect to charge at more negative values than -4 pC cm-2, values of r at other charges were calculated from the Langmuir isotherm with the equation : by introducing at each charge the appropriate values for Ts and p. Fig. 8 shows the variation!of AYq5 with coverage at constant charge. This plot supports the view that isotherms are congruent at 0 < - 4 pC cm-2 and not congruent at CT > - 4 pC cm-2.The final value of -2.8 pC cm-2 for omax was derived by plotting the slopes of the straight lines in fig. 8 as a function of CT. Fig. 9 shows that the slopes change r = [Bxor,/(l +Pxor,>lrs (2) L - - * * A L*. - ' - * * h e . a . * - . - 4 - 0.2 I- - 0.3 - 0.4 - I 0 -1 4 -0.9 - I I I I I I 2 3 4 BD surface concentration, I'x 10lO/mol cm-2 FIG. 8.-Change in inner layer potential drop of a Hg electrode upon adsorption of BD from aqueous solutions. Base electrolyte : (0) 0.25 mol dm-3 NaF, capacity data ; (0) 0.25 mol dm-3 NaF, electrocapillary data ; (A) 0.1 mol dm-3 Na2S04, electrocapillary data. Figures by the fines indicate the charge on the metal. The arrow indicates the position of the adsorption maximum.PULIDORI, BORGHESANI, PEDRIALI, DE BATTISTI AND TRASATTI 87 0.2 - I c( 8 k -0.1 - 3 2 0.1- *i 0 - > \ h -0.2- W -0.3 - 0 -0.4 I 5 0 -5 -10 - 15 o/pC cm-2 according to eqn (3) from fig.6(a). The arrow indicates the position of omax. FIG. 9.--Initial slopes of the lines in fig. 8 plotted as a function of charge. (---):Calculated ti E 0 Y - b 0.2 v 0. I 0 - -0.2 -- -5 I 2 3 4 BD surface concentration, r x 101O/mol cm-2 FIG. 10.-Change in charge at constant inner layer potential drop upon adsorption of BD on a H g electrode. The arrow indicates the position of am=.88 ADSORPTION AT Hg-SOLUTION INTERFACE linearly with Q at charges more negative than -4. The linear portion in fig. 9 is quantitatively related to the slope in fig. 6(a) by the equation :30* 31 The straight line in fig.9 has been calculated with eqn (3) from the slope of the straight line in fig. 6(a). Points for 0 > -4 have been derived from the initial slope of the curves in fig. 8. Since :309 31 a26y#prao = - 2.3 m ( a 2 log p/aa2)). (3) ( a ~ y $ p r ) , = -2.3 R T ( ~ log ppQ) (4) the lower values for aAy4/aa are an indication of lower slope of the charge dependence of AG,Dd at the given charge, which is in agreement with the results in fig. 7. 0 0.03 1 I I I 2 I 3 4 I BD surface concentration, r x 101o/mol cm-2 FIG, 11.-Reciprocal of the inner Iayer capacity at constant amount adsorbed plotted as a function of BD surface concentration. Figures indicate the charge on the metal. Fig. 10 shows the change in B as a function of r at constant inner layer potential drop.Plots are apparently strictly linear between -0.7 and -0.2 V whereas at -0.1 V (and probably at 0 V) corresponding to charge around -3.5 pC there is some evidence for non congruence. This is expected from the concentrationPULIDORI, BORGHESANI, PEDRIALI, DE BATTISTI AND TRASATTI 89 TABLE 3 .-PARAMETERS OF BUTANE-1 ,~-DIOL ADSORPTION ON POLARIZED Hg ELECTRODES FROM AQUEOUS SOLUTIONS OF NOT SPECIFICALLY ADSORBED ELECTROLYTES this work ref. (10) isotherm oniax rs Langmuir -2.8 pC cm-2 (r 3 0) to - 3.7 (r+ rs) 4 . 1 x 10-lo mol cm-2 (a neg. to - 3 pC cm-2) 4.08 x 10-lo mol cm-2 (a = - 3) - 3.71 kcal mo1-1 - 3.69 kcal mo1-l 0.0076 p C 2 cm4 (a neg. to - 3) 1 . 9 4 V-2 (E neg. to -0.55 V) 0.14 to 0 . 1 5 V 11.7f 0.3 pF C M - ~ [4.25-0.16(0+4)]~ 10-l' (0 POS. to -3) Langmuir - 2.5 pC cm-2 4.37 x mol cm-2 - - 3.72 kcal mol-1 0.0065 pC-' cm4 1.78 V-2 0 .1 (estd.) - - dependence of Em,,. At 0.1 and 0.2 V there is no evidence for any curvature and strict linearity may again be assumed. The inner layer capacity at constant amount adsorbed can be related straight- forwardly to the structure of the adsorbed layer. From fig. 8, values of AY4 were plotted as a function of charge at constant amount adsorbed and the resulting curves differentiated at constant charge. l 2 Results are shown in fig. 11 in the form of plots I01 I I I I I 2 3 4 BD surface concentration, r x 101O/mol cm-2 FIG. 12.-Inner layer capacity at constant amount adsorbed plotted as a function of BD surface concentration. Figures indicate the inner layer potential drop.90 A D SORPTION A T Hg-S 0 L U TI 0 N I NT ERF A CE of l/Ci against r.All curves converge towards a common value of Ci at r = Ts. This is the capacity for a monolayer of BD and its value has been found to be 11.7 _+ 0.3 pF cm-2. Table 3 summarizes all the adsorption parameters. Results of Dutkiewicz et are also reported for comparison. Linear relationships, as expected from congruence with respect to charge, are found for charges between -4 and - 12. At charges more positive than -4 the plots are non linear. In order to investigate congruence with respect to potential, values of Ci at constant A:+ were derived by differentiating charge against potential curves at a constant amount adsorbed, as obtained from fig. 8. Results are shown in fig. 12.At potentials between 0 and 0.2 V linear relationships between Ci and r may be assumed. Between -0.1 and -0.3 V plots are certainly non linear whereas for more negative potentials, while they are still non linear, the plots depart only very slightly from linearity. Results in fig. 12 may explain the apparent simultaneous congruence of isotherms with respect to both electrical variables at negative charge and potentials. However, they also indicate that plots like those in fig. 10 are much less sensitive than those in fig, 8 so that the former can hardly be used as a criterion for non congruence. This is implicit also in the work by Dutkiewicz et al." It is easy to show that the small curvature in the plots of Ci against r at potentials more negative than -0.2 V is a consequence of an almost undetectable curvature in the plots in fig.10 at the same AY4. Scatter of experimental points may well obscure this effect. DISCUSSION With reference to the plate capacitor formula, the adsorption of BD appears to be better described ' 9 2* 30 by a model at constant dielectric constant, E, on the negative side and by a model at constant thickness, d, of the adsorbate layer on the positive side of the adsorption maximum. The apparent congruence of isotherms over all the charge range as claimed by Dutkiewicz et is presumably to be related to the relatively low coverages reached in that investigation. This work supports Damaskin's continual caution 4* '* l 2 regarding the reliability of simultaneous congruence with respect to both o and E.The prerequisite for either of the models to hold throughout is that the solvent behaviour should be field independent.12 In reality Co, the capacity of the interfxe at 9 = 0, almost doubles from the extreme negative end to the extreme positive end of the range investigated. Thus, Cl/Co = 0.7 at strong negative charges and the decrease in capacity upon adsorption may entirely be accounted for by a change in thickness, with dH20 = 0.28 and dsD = 0.42 nm. This implies that EBD N &H20. Actually, the bulk dielectric constants of the lower diols 32-34 are comparable with, but smaller than that of water.35 However, the high frequency dielectric constant (more relevant here) of propylene-1,2-diol 34 is only slightly less than E for water.35 It is expected that the same is true of BD.Co increases as the charge becomes more positive as a result of increase in orientation polarizability of the solvent.36 Thus, the effect of decrease in E progres- sively prevails over the effect of increase in thickness and the model describing adsorption turns from one of two series capacitors to one of two parallel capacitors. The non-linear dependence of AY4 on r in fig. 8 at positive charges is evidence for strong reorientation of the molecules. This is in fact implied in the two parallel capacitor 37 In the present case, reorientation of water molecules upon BD adsorption is thought to take place as their position with respect to the adsorbate molecules becomes critical as a consequence of rotation under the action of the fieid.9. 36PULIDORI, BORGHESANI, PEDRIALI, DE BATTISTI AND TRASATTI 91 The curvature of the quadratic dependence of Actd on charge or potential is a measure of the difference in polarizability per molecule of adsorbate between organic molecule and solvent.The following relationships hold :30 (co - c,) = 2.3 RTr,(a2 log pjaE2) (1 / C , - 1 /Co) = 2.3 R T rS(a2 log P/aa2) ( 5 4 (5b) for the two parallel capacitor model, and : for the two series capacitor model. Since in the range of AYq5 0.2 to -0.1 V the mean value of Co is - 30, eqn (5a) predicts 3.8 V-2 for the slope of the steeper straight line in fig. 6(b). This value fits satisfactorily to the experimental points which, however, are more likely to follow a curved line. Conversely, at potentials more negative than the adsorption maximum the mean value of Co is 20 pF cm-2.Eqn (5a) predicts in this case a slope of 1.7 V-2 whereas that experimentally observed is 1.94 V-’. Accordingly, eqn (5b) predicts for the curvature of the (A&, charge) relationship at strongly negative charges the value of 0.0073 p C 2 cm4, while the observed value is 0.0076 P C - ~ cm4. At charges more positive than a,,, the predicted mean slope would be 0.0108 whereas in fact it may be at most even lower than the former. The charge at maximum adsorption is -2.8 at low 8 shifting to about -3.7 at high coverage. Consideration of molecular polarizability predict * a charge of maximum adsorption of - 1.7. A normal component of fixed dipoles with the positive end towards the electrode can explain the observed value of om,,.Molecules are thus thought to lie flat on the surface with the two OH groups slightly turned towards the solution. This view is supported by the small positive value of 0.07 to 0.08 contributed by adsorbate molecules to the adsorption potential shift at CT = 0 amounting (fig. 3) to 0.14 to 0.15 V, 0.07 V of which are due to displacement of oriented water molecules. 39 BD adsorption according to a Langmuir isotherm is understandable in terms of the complex nature of the interaction parameter A in eqn (1). In adsorption from solutions particle-particle interactions occur via solvent molecules occupying other- wise free sites. Thus, it is possible to write : where Go (negative quantities) are interaction free energies and s and P stand for solvent and particle, respectively.Since the adsorption layer actually is a two- component fluid, A 2 0 corresponds to complete miscibility on the surface, and A < 0 to partial miscibility. The difference between A = 0 and A > 0 may be described in terms of a disordered or an ordered structure of the interfacial layer, respectively. In the limit, the phenomenon of surface condensation40 may be observed : this is the experimental manifestation of complete immiscibility. In terms of eqn (6), constancy of A over all the charge range means that possible variations in the various terms compensate almost completely. When the charge becomes more positive than -4 pC cm-2, corresponding to about the position of zero net dipole orientation for water molecules,36 the position of the latter tends to favour stronger interaction with the adsorbate due to the opposite orientation of the molecular dipole^.^ A is thus expected to shift from zero to increasingly positive values.A decreasing value of rs, as actually found experimentally, implies that fewer molecules can be accommodated on the surface at saturation ; this, qualitatively, corresponds to the onset of some If BD binds surrounding H,O molecules more strongly than they are bound to other solvent molecules, the former become a part of the adsorbate and are no longer replaced by other BD molecules. A = -(2GLp-Gg-p-GLs)/RT (6)92 ADSORPTION AT Hg-SOLUTION INTERFACE This effect is expected to increase as the charge becomes increasingly positive. The higher value of AGld at positive charges may be understood consistently.The authors are grateful to Dr. R. Parsons for the use of his computer programs. Financial support by the National Research Council (C.N.R., Rome) is gratefully acknowledged. R. Parsons, Rev. Pure Appl. Chem., 1968,7, 91. S . Trasatti, J. Electroanulyt. Chem., 1974, 53, 335. R. Parsons, Proc. Roy. SOC. A, 1961,261,79. S. K. Rangarajan, J. Electroanalyt. Chem., 1973, 45, 279. S. K. Rangarajan, J. Electruunalyt. Chem., 1973, 45, 283. B. A. Abd-El-Nabey and S. Trasatti, J.C.S. Faraday I, 1975,71, 1230. A. De Battisti, V. Faggiano and S. Trasatti, J. Electruunalyt. Chem., 1976, 73, 327. lo E. Dutkiewicz, J. D. Garnish and R. Parsons, J. Electruanulyt. Chem., 1968, 16, 505. l1 B. B. Damaskin, Elektrukhim., 1975, 11, 428.l 2 A. N. Frumkin, B. B. Damaskin and A. A. Survila, J. Electronalyt. Chem., 1968, 16, 493. l3 S. Trasatti, J. Electruunalyt. Chem., 1970,28, 257. l4 J. D. Garnish, Ph.D. Thesis (University of Bristol, 1966). l 5 J. Lawrence, R. Parsons and R. Payne, J. Electruanalyt. Chem., 1968, 16, 193. l6 S. Trasatti, J. Electruanalyt. Chem., 1971, 31, 17. R. Payne, J. Electruanalyt. Chem., 1975, 60, 183. l8 A. De Battisti, R. Amadelli and S. Trasatti, J Culluid Interface Sci., 1978, in press. l9 D. M. Mohilner, L. W. Browman, S. J. Freeland and H. Nakadomari, J. Electruchem. SOC., 2o D. M. Mohilner and H. Nakadomari, J. Electruanalyt. Chem., 1975, 65, 843. 22 A. De Battisti and S. Trasatti, J. Electruanalyt. Chem., 1974, 54, 1. 2 3 B. A. Abd-El-Nabey, A. De Battisti and S. Trasatti, J. Electruanalyt. Chem., 1974, 56, 101. 24 N. B. Grigoryev, S. A. Fateev and I. A. Bagotskaya, Elektrukhim., 1972, 8, 583. 25 K. Doblhofer and D. M. Mohilner, J. Phys. Chem., 1971, 75, 1968. 26 A. De Battisti, B. A. Abd-El-Nabey and S. Trasatti, J.C.S. Faraday I, 1976, 72,2076. 4B. B. Damaskin, Electrokhim., 1969, 5, 771. ’ A. De Battisti and S. Trasatti, J. Electruunalyt. Chem., 1973, 48, 213. 1973, 120,1658. J. E. B. Randles, B. Behr and Z. Borkowska, J. Electroanulyt. Chem., 1975, 65, 775. A. N. Frumkin and B. B. Damaskin, Modern Aspects ofElectrochemistry, ed. J. O’M. Bockris and B. E. Conway (Butterworth, London, 1964), vol. 3, p. 149. 28 R. Parsons, Modern Aspects of Electrochemistry, ed. J. O’M. Bockris (Butterworth, London, 1954), p. 103. 29 Interatomic Distances. Supplement (The Chemical Society, London, 1965). 30 R. Parsons, J. Electruanalyt. Chem., 1963, 5, 397. 31 R. Parsons, Trans. Faruday SOC., 1959,55,999. 32 J. Wumbel, F. Jona and E. P. Scherrer, Helv. Phys. Acta, 1959, 39, 412. 33 C. P. Smyth and W. S. Wells, J. Amer. Chem. SOC., 1932, 54, 2261. 34 D. W. Davidson and R. H. Cole, J. Chem. Plzys., 1951, 19, 1484. 35 J. B. Hasted, Water. A Comprehensive Treutise, ed. F. Franks (Plenum Press, New York- 36 S. Trasatti, J. Electrounalyt. Chem., 1975, 64, 128. 37 B. B. Damaskin and A. N. Frumkin, J. Electrunulyt. Chem., 1972, 34, 191. 38 S. Trasatti, Ext. Abstrs., 27th ISE Meeting (Zurich, 1976), p. 207. 39 A. De Battisti and S. Trasatti, Croat. Chem. Actu, 1976, 48, 607. 40 S. L. Dyatkina, B. B. Damaskin, N. V, Fedorovich, E. V. Stenina and V. A. Yusupova, London, 1972), vol. 1, p. 255. Elektrukhim., 1973,9, 1283. (PAPER 7/735)

ISSN:0300-9599    

DOI:10.1039/F19787400079

出版商:RSC    

年代:1978

数据来源: RSC

摘要:

Transport in Aqueous Solutions of Group IIB (298.15 K) Part 3.-Isotopic Diffusion Coefficients for Cadmium-1 15 Ions in Iodide Metal Salts Aqueous Cadmium BY RUSSELL PATERSON" AND LUTFULLAH? Department of Chemistry, University of Glasgow, Glasgow G12 8QQ Received 6th May, 1977 Cadnlium isotopic diffusion coefficients (Daa) were determined in aqueous cadmium iodide in the concentration range 0.1-0.6 mol dm-3. Daa passes through two maxima, one below 0.1 mol dm-3, the other at 0.4 mol dm-3. Irreversible thermodynamic analysis shows that these maxima are due to positive fluctuations in the isotope-to-isotope coupling contributions to Daa. For these studies a modified diaphragm cell technique was developed. In previous papers 1 * the isothermal vectorial transport properties of aqueous cadmium iodide have been reported and analysed using the methods of irreversible thermodynamics.The anomalous transport properties of this salt are intimately connected with the degree to which it is self-complexed in solution. With a knowledge of the concentrations of these complexes, it has been shown that the transport behaviour could be predicted in dilute solutions.2 In this work the study of transport in cadmium iodide solutions has been extended to include isotopic diffusion ; diffusion coefficients have been measured for cadmium- 115 ions in cadmium iodide over the range 0.1-0.6 mol dm-3. For this purpose a new design of the Stokes diaphragm cell has been devised to provide simultaneous multi-cell determinations in a thermostat of normal dimensions. Isotopic diffusion coefficients for cadmium, D,,, have been shown to have a quite anomalous dependence upon the concentration of bulk salt, fig.3. The curve shows two maxima and all measured diffusion coefficients are larger than that at infinite dilution, Di, (7.12 x cm2 s-l). Comparison with other literature data shows that maxima in relatively concentrated solutions may be caused by the increasing presence of solvent-order destroying iom4 In concentrated cadmium iodide solutions, free iodide and the higher complexes CdI, and CdIi- may cause this effect. The maximum in dilute solutions has no precedent, however. Irreversible thermodynamic analysis of this data has been made, using previously determined binary mobility coefficients for cadmium (La,) and experimental diffusion coefficients, D,,, to determine isotope-isotope coupling coefficients. It is shown that these coupling coefficients are primarily responsible for the observed maxima in Daa.A theoretical analysis and prediction of the factors influencing isotope coupling in coinplexed electrolytes is deferred to the following paper.5 This, combined with earlier predictions of binary mobility coefficients allows the diffusion coefficients for cadmium to be calculated as a function of concentration in dilute solutions, including the first maximum in D,,, fig. 3. ? Present address : Institute of Physical Chemistry, University of Peshawar, Peshawar, Pakistan. 9394 TRANSPORT IN AQUEOUS SOLUTIONS EXPERIMENTAL The Stokes diaphragm cell technique provides a convenient and accurate method for determining diffusion coefficients in solution.Commonly a U-shaped permanent magnet is mounted coaxially with the diaphragm cell and, when rotated, it drives two internal magnetic stirrers, which are positioned above and below the diaphragm. Most variations of this method involve modifications to the stirring In general, the conventional rotating assembly or its slightly modified form is preferred. There are, however, certain disadvantages to the conventional methods. The diaphragm itself may be worn by the action of the stirrers rotating on its upper and lower surfaces. This effect can be allowed for by recalibration lo or avoided by adjusting the stirrers to that they do not quite touch the diaphragm when inuse.l The major experimental inconvenience is, however, the unwieldiness of the magnet assembly with its associated gearing and motor drive.It is seldom convenient to operate more than one cell in a normally sized thermostat. For the above reasons the design of both the stirrers and their driving mechanism was reconsidered. Two bar magnets were mounted on a small Perspex turbine, which enclosed the diffusion cell. The turbine was rotated by a jet of water pumped from the thermostat bath itself. Since the turbine unit is compact, several cells may be used simultaneously in a relatively small thermostat bath. A unit capable of accommodating four such cells fitted into a thermostat (64 x 46 x 41 cm3) and was driven by a single pump. THE DIAPHRAGM CELL A Pyrex glass standard filter tube with sintered glass disc (porosity No.4; 3790/68, Jobling Pyrex, London) was used to construct the cell. The upper stirrer within the cell was made by enclosing a soft iron wire in a medium walled Pyrex glass tube and attaching FIG. 1 .-Schematic representation of the diaphragm cell, including internal stirrers. Also shown are the top plug, with internal capillary and air-leak and the bottom plug made to the design of Mills and Woolf, ref. (9), with A, body of fibreglass-impregnated Teflon ; B, stainless steel valve ; C, brass adjustment knob ; D, locking nut ; E, side vents ; F, plugs and G, O-rings of neoprene rubber.R . PATERSON AND LUTFULLAH 95 two side blades at right angles to form a flat four-bladed unit, fig. 1. These blades were slightly shorter than the internal diameter of the filter tube.A central shaft of Pyrex glass was sealed to the stirrer blades. This passed through a glass collar and its end was melted to form a small spherical knob which rested on the flanged top of the collar, fig. 1. The collar was then fused to the side wall of the cell with a short length of glass rod, such that the stirrer blades rotated centrally in the cell, some 2mm above the upper surface of the diaphragm. The stirrer in the bottom compartment was constructed similarly, except that the solid sphere on the central rod was adjacent to the stirrer blades, thus holding them at the same distance below the diaphragm. A diagram of the cell and stirrer units is given in fig. 1. The action of the stirrers in both compartments was tested to ensure smooth rotation.The ends of the filter tube were terminated with B-19 standard ground glass joints. The top plug was of standard design and contained a central capillary, terminated with a B-7 ground glass socket, fig. 1. The useable capacity of the cell was marked as the upper limit of this internal capillary. In use, the top B-7 socket was fitted with a very fine drawn out glass capillary. In this way the cell was not completely sealed, and thus allowed for volume changes due to mixing (when calibration experiments involving potassium chloride solutions were made). The bottom plug, fig. 1, was constructed to the design of Mills and Woolf and incorporated a valve mechanism to ensure 1 complete filling of the lower compartment. FIG. 2.-Schematic representation of the water-driven turbine and H its casing.Turbine rotor: (C) cuts made into the turbine rotor for magnets, (M) ; (H) central hole ; (P) paddle drilling around the periphery. Turbine casing: (B) base which is filled with mercury to a depth of 3 mm in use; (I), inner wall ; (0), outer wall ; (N), nozzle imput for pump water ; (H), central hole to fit around diaphragm cell ; (L), lugs for mounting turbine assembly upon supporting tray.96 TRANSPORT I N AQUEOUS SOLUTIONS TURBINE UNITS AND SUPPORTING TRAY The turbine is shown diagrammatically in fig. 2. It was constructed from a solid Perspex disc (95 mm in diameter and 25 nim thick) through which was bored a central hole 52 mm in diameter. A standard 3” (9.5 mm) drill was then used to machine twelve tangential paddle grooves, each to a maximum depth of 5 mm from the circumference of the turbine.Two rectangular slots 20 mm deep and 13 min square were cut sym.etrically into the inner side of the turbine, to hold two permanent bar magnets. These magnets were wrapped in p!astic tape and push-fitted into their positions. The turbine casing was of an open-top construction made from 35 mm lengths of 3 mm walled Perspex tubes with outer diameters of 50 and 100mm respectively. A circular sheet of Perspex formed the base of the casing. This too was bored centrally to the dimen- sions of the inner tube, giving a central hole in the turbine casing through which the diaphragm cell could pass. Prior to sealing the wall of the casing to the base, the surface of the inner wall was accurately machined so that the turbine fitted closely into the casing, but still rotated freely.The gap between the outer rim of the turbine rotor and the outer casing was 1.5 111111. A 6 mm hole in the side wall of the casing, in line with the paddle drillings on the turbine, was fitted with a 3 mm (i.d.) nozzle and provided access for a flow of water directed tangentially at the turbine rotor. No corresponding exit tube was required. In use, water pumped into the rotating turbine left by way of the gap between the turbine rotor and the outer casing. Three Perspex lugs were attached to the base of the turbine casing to fix this unit reproducibly upon its tray (described below). To provide an almost frictionless surface for the turbine rotor the turbine casing was filled to a depth of 3 mm with mercury.Four such turbines were mounted on a common tray in the thermostat. This tray was constructed from Perspex sheet (12 mm thick) reinforced with rectangular Perspex bars. The tray was perforated with 5 mm holes to allow circulation of bath liquid. Four holes, matching those of the turbines were drilled symmetrically in the tray, allowing four diffusion cells, with turbines, to be mounted in fixed positions. The tray itself was supported by four adjustable legs and could be levelled in the thermostat bath. Each diaphragm cell was held in a vertical position in the central hole of the turbine unit, using clamps attached to aluminium rods mounted on the Perspex tray. Initial adjustments were made to ensure that the cell diaphragms were horizontal and that the internal stirrers were driven smoothly by the turbine.Thereafter each cell could be removed and replaced reproducibly. WATER CIRCULATION The four turbines were driven from a single circulatory pump (Shandon, Gallenkamp, London). A variety of such pumps were used with success. To drive four turbines from this single pump, a simple distributor was constructed. This consisted of a 100ml Pyrex bulb with five 3 mm glass tubes joined to its lower end. Of these the entry tube was placed vertically below the bulb. The other four tubes were in axial positions and distributed the flow to the turbines. Each of these outflows was controlled by a TF 2/18 “ Rotafio ” tap. The central bulb of the distributor was half-filled with air when in use, and provided both a reservoir of backing pressure and served to dampen pressure fluctuations from the water pump.By adjustment of the “ Rotaflo ” taps, stirring speeds in the diaphragm cells could be held constant at rotation speeds from 10-100 rpm. OPERATION Thermostat control was obtained using a conventional mercury-toluene coiled glass thermo-regulator in conjunction with an electronic relay mechanism (type 42, Gallenkamp, London). The thermostat water was heated by two 150 W light bulbs activated by the thermo-regulator and cooled by tap-water passing through cooling coils immersed in the thermostat. In this way temperature was maintained at 298.15+0.01 K. VOLUME DETERMINATIONS Volumes of the cell compartments were determined by weight calibrations, using carbon tetrachloride.That of the diaphragm was determined independently after dropwise additionR . PATERSON AND LUTFULLAH 97 of carbon tetrachloride to the sintered glass diaphragm in an otherwise dry cell, held horizontally. The volumes of top ( VT) and bottom ( VB) compartments were each some 55 cm3 and that of the diaphragm ( VD) some 1.5 cm3. Compartment volumes were obtained reproducibly to rfI0.015 cm3 and those of the diaphragms to k0.003 cm3. DIFFUSION EXPERIMENTS The cells were filled by the “ vacuum thump ” method ;lo all solutions were filtered and degassed before use. Once the diaphragm was filled with solution using this vacuum method the bottom compartment was filled using the valve arrangment in the bottom plug (fig.l), which avoided trapping of air bubbles. The upper compartment could then be filled either with solvent (for calibration experiments, using potassium cnloride) or with the same solution (for isotopic diffusion experiments). For calibration, 0.50 mol dmW3 potassium chloride in the lower compartment diffused into pure solvent (water). In these experiments a prediffusion time of two hours was allowed to establish a uniform concentration gradient across the diaphragm. The duration of this prediffusion was estimated by Gordon’s approximation.12 It has been shown that Gordon’s estimate may overestimate the prediffusion time, but varying the length of the prediffusion time within reasonable limits has been shown to contribute no significant error.g At the end of the prediffusion the top plug was removed and the upper compartment emptied using pipettes with side holes, to prevent disruption of the diaphragm gradient.The top compart- ment was filled with pure water (25°C) once more after several rinsings. At this final filling the diffusion run proper was considered to be initiated; the top plug was replaced and the volume of the top compartment adjusted to the calibration mark in the upper capillary. A typical calibration experiment lasted 46-48 h. At the end of the experiment the upper and lower solutions were sampled and analysed by conductimetric analyses of weight-diluted samples .g For isotopic diffusion experiments the cell was entirely filled with an inactive solution of the required concentration. Diffusion experiments were initiated by injection of a small sample of the same solution traced with isotope into the top compartment. For this purpose “ Hamilton ” microsyringes, fitted with “ Chaney ” adaptors were used.Volumes added were 0.1 cm3 or less and, after addition, the excess volume was removed. This method is classed as a solvent-filled diaphragm rneth~d,~ since at time zero the diaphragm and bottom solution are sled with inactive solution and only the top compartment contains the labelled diffusing species. Diffusion experiments for cadmium-115 were allowed to proceed for 72-80 h. The isotopic content of each compartment was assayed by withdrawing accurately- known volumes for radioactive counting. Normal counting precautions were used, but to eliminate coincidence and quenching effects high activity samples were diluted with inactive solution, and upper and lower compartments were counted at similar activity levels.Samples were counted using standard scintillation procedures in 10cm3 aliquots of a dioxane-based liquid scintillator. The 1-4 dioxane solvent was purified by refluxing with ferrous sulphate (log) and sodium metabisulphate (log) per dm3 of dioxan for 1 h. If this precaution was not observed, colour quenching was severe due to production of iodine in the radioactive samples. Triplicate samples were counted and counting efficiency of G0.3 % was obtained. PREPARATION OF ISOTOPIC SOLUTION Radioactive cadmium chloride (115CdC12 as) in 0.1 mol dm-3 hydrochloric acid was obtained from the Radiochemical Centre, Amersham, England.Labelled cadmium iodide was obtained from this solution by an electrolysis technique. The electrolysis cell consisted of a Pyrex glass U-tube with a central porous disc (porosity 4). Each half cell had a capacity of approximately one ml and each was fitted with a platinum electrode, 3 mm square, electroplated with a heavy deposit of cadmium metal. The electrolysis solution was 0.1 mol dm3 cadmium chloride acidified with hydrochloric acid ; hydrazine dihydrochloride was added as depolariser. One cadmium plated electrode was mounted in each half-cell, which was then filled with the solution used for plating. To the cathodic compartment a 1-498 TRANSPORT I N AQUEOUS SOLUTIONS suitable quantity of radioactive cadmium chloride was added and cadmium-115 plated on to the cathode.When most of the activity had been transferred to this electrode, the cell solution was replaced by one of inactive cadmium iodide. The polarity of the cell was reversed and cadmium-115 iodide solutions were obtained at the desired activity. The radioactive cadmium electrode could be used to prepare a number of such solutions, as required. RESULTS AND DISCUSSION The cell constants (p) of the four diffusion cells were determined by standard rneth~ds,~. 9* lo using the gradient-filled initial state in which 0.50 mol dm-3 potassium chloride in the lower compartment was allowed to diffuse into pure solvent in the upper, after a prediffusion time during which a linear gradient had been established across the diaphragm. Barnes l3 has taken account of the fact that a true steady state diffusion condition is not created by this method and this treatment has been extended by Mills, Woolf and Watts l4 to include three initial conditions in the diaphragm.These are the gradient-filled, solvent-filled and solution-filled conditions. Only the first two are of interest in this study, since the gradient-filled condition applies to calibration experiments, using potassium chloride and solvent-filled corresponds to the conditions of isotopic diffusion. The radioactive solution is added to the upper compartment only, and so the diaphragm and lower compartment are filled with inactive solution at time zero. This latter condition is particularly convenient for isotopic studies since it involves a minimum of handling of radioactive solutions.The two methods must, therefore, be shown to be compatible. For calibration by the gradient-filled method the cell constant is defined by eqn (1) where O C B is the concentration at time zero (after prediffusion) in the bottom compartment. C, and CB are those obtained after time t / s . O C B is not obtained directly, but from these latter concentrations by eqn (2) The integral diffusion coefficient D may be obtained from literature sources using the data of Stokes 1 5 9 recently refined by Mills and Woolf.' Stirring speeds for the Stokes diaphragm cell are usually chosen in the range 50-60 r.p.m. Since modified stirrers were used in our cells, the effect of stirring rate upon cell calibration was investigated. Cell constants (j?) were obtained at 30, 60 and 85 r.p.m., for which the ratios /3/pG0 r.p.m.were 0.991, 1.000 and 0.999 respectively. The cell constant was thus unaffected by stirring speeds in the range 60-85 r.p.m. A speed of 60 r.p.m. was used for all subsequent work. Cell constants for the four cells employed, ranged from 0.44 to 0.51 and were reproducible to For isotopic experiments employing the solvent-filled initial state,14 the isotopic "CB = CB + C ~ V T +4VD)/(VB + + VD). (2) GO.1 %. diffusion coefficient, D is defined by eqn (3) (3) 1 D = - In [ OCB(l - n/6)/(cB - cT)] Pt The cell constant, /3, is identical to that defined in eqn (l), but an additional term, (1 - A/6), appears in the logarithmic term, where A is the volume ratio 2 VD/( V, + VB) : the volume of the diaphragm compared with the average volumes of the top andR .PATERSON AND LUTFULLAH 99 bottom compartments. For a successful application of Barnes' theory,13 ;t is assumed to be small. For the cells of this study 3, ranged from 0.024-0.028, which is within acceptable limits. TABLE 1 .-ISOTOPIC DIFFUSION COEFEICIENTS FOR 22Naf IONS IN SODIUM CHLORIDE (298.15 K), USED FOR CALIBRATION TEST conceatra tion C/mol dm-3 sodium chloride I I1 I11 diffusion coefficients, D X 105/cm2 s-1 0.40 1.279 1.278 1.283 I, From this work using the solvent-filled diaphragm technique and cell constant (B) from potassium chloride diffusion (0.50 mol dm-3) into water (experimental uncertainty k 0.5 %). 11, From Mills, Woolf and Watts [ref. (14) and (9)] by the methods used in I, (uncertainty k0.5 %). 111, From Mill's review, ref.(16) (original reference J. Amer. Chem. SOC., 1955, 77, 6116), using the gradient-filled technique, (uncertainty f 0.5 %). To test these equations, the isotopic diffusion coefficient for 22Na+ in aqueous sodium chloride (0.40 mol dm-3) was measured and compared with literature data.g* l 6 Excellent agreement was obtained within the experimental uncertainty of measurement (20.5 %), see table 1. ISOTOPIC DIFFUSION COEFFICIENTS FOR CADMIUM-1 15 I N AQUEOUS CADMIUM IODIDE With the calibration methods thus justified, diffusion coefficients for cadmium-1 15 in aqueous cadmium iodide were determined in the range 0.1-0.60 rnol dm-3. Results are given in table 2 and fig. 3. TABLE 2.-ISOTOPIC DIFFUSION COEFFICIENTS FOR CADMIUM-1 15 IONS IN AQUEOUS CADMIUM IODIDE (DaJ TOGETHER WITH MOBILITIES AND ISOTOPE-ISOTOPE COUPLING TERMS DEFINED IN EQN (6) DaaX 10-3IRT Laa/CE a (C,'/CiC,*) Lza x 1012 x 1012 x 1013 CE Dsa X 106 /mol dm-3 /cmz s-1 /mol em* J-1 s-1 x 10-3 0.0 0.1 0.15 0.20 0.30 0.40 0.50 0.60 7.122 7.860 *7.436 7.422 *7.898 8.114 7.884 *7.164 2.8730 3.1708 2.9997 2.9941 3.1861 3.2732 3.1804 2.8904 2.8730 3.0370 2.9788 2.8940 2.7390 2.63 18 2.5706 2.5478 O.OO0 - 1.338 - 0.209 - 1.001 -4.471 - 6.41 6 - 6.098 - 3.426 a ref.(2). The experimental uncertainty in D, is k0.5 %. Data starred in column 2 were averaged values from duplicate experiments which agreed to k0.5 %. The units of Ls8 [obtained from ref. (2)] and Lza are mo12 J-' cm-l s-l. Since the estimated uncertainty in LalCT is f 1 % the isotope-isotope coupling term, in the final column, is uncertain to 2 0.4 x 10-13 units.The concentration dependence of the diffusion coefficient for cadmium (Daa) is remarkably complex. It is notable that all experimental diffusion coefficients in the experimental range are larger than the value at infinite dilution, D$,, (7.12 x cm2100 TRANSPORT IN AQUEOUS SOLUTIONS s-l) obtained from eqn (4), using Matheson's estimate of the equivalent ionic con- ductance of cadmium at infinite dilution, A:, (53.5 cm2 Sz-l equiv-l).l' In the experimental range, D,, passes through a minimum (at 0.2mol ~ l m - ~ ) rises to a maximum (at 0.4 mol dm-3) and falls once more to a lower value at 0.6 mol dm-3. (Duplicate experiments made at 0.15, 0.30 and 0.60 niol dm-3 were reproducible to k0.5 %).No data are available at concentrations below 0.1 mol dm-3 because of the concentration limitations of the diaphragm method, but it is obvious that the diffusion coefficient must pass through a maximum value between 0.1 mol dm-3 and infinite dilution. t 6.0 1 I t I 0.0 0.2 0.4 0.6 - dC FIG. 3.-Isotopic diffusion coefficients for cadmium-115 in aqueous cadmium iodide at 298.15 K, Daa, 0. The contribution to Daa from the binary mobility coefficient term is RTLaa/CT from eqn (6), 0. [ L a values were obtained from ref. (2)]. The shaded area representing the difference between DU and RTLaaICT is a measure of the isotope-isotope coupling term, - RTLza CT/CX'.* of eqn (6) ; table 2. The dimensions of RTLaa/CT and RTLza Cz/CiC,' are those of the diffusion coefficient, Da,/cm" s-l when concentrations CT, Cz and C.* are in mol ~ r n - ~ .Hertz, Holz and Mills have shown that maxima in ionic diffusion coefficients may be obtained when solvent-order producing ions are present. Such effects occur only at high concentrations; iodide ion has shown to be effective. It is possible that the second maximum in fig. 3 arises from such solvation effects caused by increasing concentrations of free iodide and the order-destroying complexes CdI; and CdI;-. (The distribution of species is shown in fig. 4 of Paper 2 2). Olsztajn, Turq and Chemla,l* in their studies of isotopic diffusion of cadmium and zinc ions in potassium chloride, observed that diffusion coefficients increased with concentration of supporting electrolyte.No maxima were observed, but the increasesR . PATERSON AND LUTFULLAH 101 were tentatively ascribed to the presence of increasing concentrations of the order- destroying complexes CdCli- and ZnCla- in these solutions. The maximum for D,, in dilute solutions has no parallel in published data on binary electrolytes. Some dissociated electrolytes in fact show minima due to the steep decrease from infinite dilution value predicted by the Onsager limiting law. It is obvious that the complexed nature of cadmium iodide precludes direct application of Onsager theory. This theory is, however, developed to include complexed electrolytes in the following paper.5 IRREVERSIBLE THERMODYNAMICS Sufficient experimental data are available to make a formal irreversible thermo- In earlier papers 1 9 9 2o it was shown that the isotopic diffusion coefficient of an dynamic analysis of the cadmium diffusion results.ion of species a in a solution of salt (a, b) may be represented by eqn (5) In eqn (5) Cz is the total concentration of species a (mol dm-3) and C,* and C,O are the concentrations of isotopically labelled and unlabelled ions, such that C,* + C,O = C z . (With RTexpressed as J mol-l and La, as mo12 J-1 cm-l s-l, D,, is expressed as cm2 s-l). La,, the binary mobility coefficient of cadmium, is known from earlier studies.2 The remaining isotope-isotope coupling coefficient Lza may, therefore, be calculated, table 3. At infinite dilution the isotope term -L:aCf/CfC,O in eqn ( 5 ) is zero, and so the diffusion coefficient is determined solely by the intrinsic mobility L,JC:.It is pertinent, therefore, to examine the degree to which this parameter determines D,, when the concentration is increased, and how important are the coupling interactions between the labelled and unlabelled cadmium species in that solution. It is obvious from table 3 and fig. 3 that both maxima in D,, are due to positive fluctuations in the isotope-isotope coupling term in eqn (5). a method was developed for predicting all transport properties of the unlabelled salt, including the function L,,/Cz, which appears in eqn (5). In the following paper in this series, this treatment has been extended to include isotopic experiments in self complexed electrolytes. Isotope-isotope coupling is predicted and the diffusion coefficients (D,,) calculated for cadmium iodide in dilute solutions. In Paper 2 We are grateful to the Pakistan Ministry of Education for a grant to Lutfullah. R. Paterson, J. Anderson and S. S. Anderson, J.C.S. Furaduy I, 1977,73, 1763, Part 1. R. Paterson, J. Anderson, S. S. Anderson and Lutfullah, J.C.S. Furaday I, 1977, 73, 1773, Part 2. R. A. Robinson and R. H. Stokes, Electrolyte Solutions (Butterworth, London, 2nd edn, 1968). H. Hertz, M. Holz and R. Mills, J. Chim. phys., 1974, 71, 1355. R. Paterson and Lutfullah, J C.S. Faraduy I, 1978,74, 103, Part 4. J. M. Nielson, A. W. Adamson and J. W. Cobble, J. Amer. Chem. SOC., 1952, 74, 446. ’ J. B. Lewis, J. Appl. Chern., 1955, 5, 228. * F. A. L. Dullien and L. W. Shemilt, Canad. J. Chem. Eng., 1961,39,242. R. Mills and L. A. Woolf, The Diaphragm Cell (Australian National University Press, Canberra, 1968). lo G. J. Janz and G. E. Mayer, Diflusion of Electrolytes : Principles and Practice of the Diaphragm Cell Technique ( U . S . Office of Saline Water, Report, 1966). l1 S. K. Jalota and R. Paterson, J.C.S. Faraday I, 1973, 69, 1510. l2 A. R. Gordon, Ann. N. Y. Acad. Sci, 1945,46,285.102 TRANSPORT IN AQUEOUS SOLUTIONS l3 C. Barnes, Physics, 1934, 5,4. l4 R. Mills, L. A. Woolf and R. 0. Watts, A.I. Chem. Eng. J., 1968, 14, 671. l5 R. H. Stokes, J. Amer. Chem. SOC., 1951, 73, 3527. l6 R. Mills, Rev. Pure Appl. Chem. (Australia), 1961, 11, 78. R. A. Matheson, J. Phys. Chem., 1962, 66,439. M. Olsztajn, P. Turq and M. Chemla, J. Chim. phys., 1970,67,217. l9 J. Anderson and R. Paterson, J.C.S. Faraday I, 1975, 71, 1335. 2o S. Liukkonen, Actu Polytechnica Scand., Chemistry Incl. Metallurgy Series No. 113, Helsinki, 1973. (PAPER 7/769)

ISSN:0300-9599    

DOI:10.1039/F19787400093

出版商:RSC    

年代:1978

数据来源: RSC