摘要:

October, 19501 t’ESKATARAMASIAH AKD KAGHAT’A KAO 553 Separation of Thorium from the Ceria Earths and its Application. to the Analysis of Monazite BY M. VENKATARAMANIAH AND BH. S. J7. RAGHAVA RAO SY;\roPsIs-Thoria can be separated from the ceria earths in ratios up to 1 : 16 by a single precipitation with sodium naphthionate in nearly neutral solution. The minimum amount of thoria that can be satisfactorily deter- mined is about 9 mg. The method can be used for the determination of thoria in the rare earths obtained from monazite. THE importance of thorium in fission studies has stimulated interest in the chemistry of the element and in particular in its analytical reactions. Monazite still remains the chief source of thorium and the separation of the element from the associated cerite earths is a problem of some comp1exity.l With the exception of the iodate method of Meyer and Speter,2 which is both cumbersome and expensive, all reported procedures require preliminary removal of zirconia and phosphoric acid.In addition, double and sometimes triple precipitations are necessary for the effective removal of ceria earths. Whilst retaining the former dis- advantages the procedure described in this paper offers a simple but accurate method of separating thoria by a single precipitation. PROCEDURE- Make the solution, containing not more than 0-2 g. of thoria, just acid to Congo red. The exact acidity is important, because if the solution is more acid, precipitation of thoria is not complete, and if the acidity is lower, the precipitate is flocculent and retains large amounts of the mother liquor, making later washing difficult and even ineffective.These qualitative directions are sufficient to carry out a separation. It has, however, been found that if the pH of the solution is lower than 2.3, precipitation of thoria is incomplete, and contamination with ceria begins at a pH of 3.2. Dilute the solution to 100ml. and boil. To the boiling solution add slowly and with constant stirring 100 ml. of a boiling 10 per cent. solution of sodium naphthionate. A pink crystalline precipitate forms a t once. Continue boiling for 5 to 10 minutes and set aside to cool. Filter the cold liquid through a 9-cm. Whatman Xo. 42 filter-paper and wash the precipitate three times by decantation with cold water and finally four or five times on the filter-paper.To determine the ceria earths, add ammonia to the filtrate and washings until the solution is alkaline. Filter, wash, ignite and weigh the precipitate as ceria earths; a correction for excess oxygen over R20, is made by dissolving in hydrochloric acid and potassium iodide and titrating the liberated iodine with sodium thiosulphate. Ignite wet, and weigh as Tho,. RESULTS- of thoria and ceria earths. DETERMINATION OF THORIUM IN MOXAZITE- The mixture of thoria and rare earth oxides obtained from a 30-g. sample of monazite from Travancore, India, according to the procedure prescribed by Miner,3 and freed effectively from phosphoric acid by double precipitation with oxalic acid, is dissolved in concentrated nitric acid and a few ml.of hydrogen peroxide to reduce CeIV to CeII’, and the solution is evaporated almost to dryness on a water-bath. The residue is dissolved in water and the solution made up to 500 ml. In 25 ml. of this solution the thoria and the ceria earths are determined as described above. The results of four analyses made in this way together with two by Neish’s m-nitrobenzoic acid method* (double precipitation) are shown in Table 11. Table I gives the results obtained by this method with thoria and artificial mixtures554 VEKKATARAMASIAH AND RAGHAVA RAO [Vol. 75 TABLE. I APPLICATIOX OF PROPOSED METHOD TO -1RTIFICAL MIXTURES Tho, taken, g- 0.0087 0.0087 0.0087 0.0087 0.0438 0.0438 0.0875 0.0875 0.0875 0.0875 0.0875 0.0875 0-0875 0.0875 0.0875 0-0875 0.0875 0.0875 0.1750 0.1760 R,03 added, g .nil nil 0.0866 0.0866 0.0866 0.0866 nil nil 0-0700 0.0700 0.2915 0.291 5 0.5130 0.5830 0.85'45 0.85'45 1.4575 1.4575 1.4576 1.4675 Tho, found, g . 0-0088 0.0089 0.0088 0.0087 0.0440 0.0437 0.0878 0-0876 0.0873 0.0874 0.0874 0.0876 0.0876 0-0877 0.0875 0.0877 0.0873 0.0875 0.1752 0.1748 TABLE: I1 Sodium naphthionate method Neish's nz-nitrobenzoic acid method -- r- A 1 Tho,, R203P Tho,, R2°3* g. g . g* g. 0.1314 0,7595 0.1315 0.7596 0.1317 0.7594 0.1318 0.7592 0.1312 0.7596 0-1316 0.7592 SUMMARY AND CONCLUSIONS In neutral nitrate solution sodium naphthionate under proper conditions effects in a single precipitation complete separation of thoria from up to sixteen times the weight of ceria earths. As little as 9 mg. of thoria can be satisfactorily determined. The method has been successfully applied to the determination of thoria in monazite. The reagent offers a distinct advantage over others so far suggested. REFERENCES 1. 2. 3. 4. Moeller, T., Schweitzer, G. K., and Starr, D. D., Cheurz. Rev., 1918, 42, 64. Meyer, R. J., and Speter, >I., Chew. Ztg., 1910, 34, 306. Miner, H. S., U.S. Bureau of Mines,.1923, Bulletin KO. 212, p. 53. Neish, A. C., Chew h-ews, 1904, 90, 196. CHEMICAL LABORATORIES ANDHRA UNIVERSITY WALTAIR, INDIA First submitted, November, 1949 Amended, March, 1950

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DOI:10.1039/AN9507500553

出版商:RSC    

年代:1950

数据来源: RSC

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October, 19501 PURUSHOTTAM AND RAGHAT’A KAO 555 The Use of Tannin in the Estimation of Zirconium and its Separation from Thorium BY A. PURUSHOTTAM AXD BH. S. V. RAGH-41’A RAO SYNoPsIs-Zirconium is quantitatively precipitated by tannin from a chloride solution up to 0.15 N in hydrochloric acid. By double precipitation at this acidity it can be quantitatively separated from thorium. SCHOELLER~ put forward a claim for tannin as a selective reagent for zirconium, but his results in its separation from thorium are not quite convincing in that his total zirconium dioxide values are high and even in the one instance of close agreement the zirconium dioxide precipitate contained some thorium. A careful perusal of Schoeller’s results showed that a fuller study of the precipitation of zirconium under various conditions might throw further light on the problem and yield fruitful results.With this object, the effect of acidity on the precipitation of zirconium by tannin was studied and the results were utilised to devise a procedure for its separation from thorium. EXPERIMENTAL DETERMINATIOX OF ZIRCONIUM- From a stock solution of pure zirconyl chloride in 0.1 A’ hydrochloric acid, 20-ml. portions were taken and the zirconium content was determined by precipitation with mandelic acid2 and with m-nitrobenzoic acid.3 The mean weights of ZrO, obtained were 0.0550g. and 0.0552 g. respectively. From the weighted mean of a21 the results the ZrO, content of the solution was taken as 0.0550 g. per 20 ml. Aliquots (20 ml.) of this solution were neutralised by careful addition of calculated quantity of ammonia or further acidified with 2 2\r hydro- chloric acid to bring the acidity to the desired value when diluted to 200 ml.; 10 ml. of saturated ammonium chloride solution were added and the solution was diluted to 175 ml. and boiled. A freshly prepared solution of 1 g. of tannin in 25 ml. of water was then added, and the resulting precipitate was allowed to settle, filtered, washed with a 2 per cent. solution of ammonium dhloride and ignited to ZrO,, following the directions given by Schoeller. The results obtained are given in Table I. * TABLE I EFFECT OF ACIDITY ox PRECIPITATION OF ZIRCONIUM DIOXIDE Conditions of precipitation %-eight of ZrO,, g* 0.0553 Just neutral to Congo red . . .. . . I 0.0552 0.0550 1 0.0549 0.1 A; hydrochloric acid .. .. .. 0.0550 * { 0-0553 0-0550 0.15 h‘ hydrochloric acid . . . . . . . . I 0.0549 7 0.0548 I 0.0549 0.2 N hydrochloric acid . . .. .. 0.0541 * { 0.0539 These results show that precipitation of zirconium is complete in solutions up to 0.15 N in hydrochloric acid; at higher acidity, part of the metal remains in solution. In confirma- tion, when the filtrate from the two experiments in 0.2 N hydrochloric acid was neutralised, a slight turbidity resulted.556 PURUSHOTTAM Ah’D RAGHAVA RAO [Vol. 75 SEPARATION OF ZIRCONIUM FROM THORIUM- A semi-quantitative test revealed that in 0.15 N hydrochloric acid there was no immediate precipitation of thorium and only a slight turbidity occurred on boiling for half an hour. If zirconium is present, however, fair quantities of thorium may be co-precipitated.In the following experiments, to the combined zirconium and thorium solutions, 1.5 g. of tannin (as against 1 g. previously) in 25 ml. were added, and the solution was boiled for 2 minutes after addition of the reagent. The precipitate was allowed to settle for 2 hours, filtered through a Whatman KO. 42 filter-paper, washed and ignited to ZrO,. The results are given in Table 11. TABLE I1 ZrO, taken = 0.0550 g.; acidity = 0.15 I\i PRECIPITATION OF ZIRCONIUM DIOXIDE I N PRESENCE OF THORIUM Expt. KO. Tho, added, ZrO, weighed, 1 0.1740 0.0623 2 0.1740 0.0621 3 0-0870 0.0594 4 0.0870 0.0594 g. g- In all these experiments the filtrate was free from zirconium. The filtrate in experiment 1 was evaporated to dryness and the residue ignited and fused with potassium pyrosulphate, the melt extracted with water, and the solution tested qualitatively with sodium hydrogen phosphate in 10 per cent.sulphuric acid. No trace of zirconium was detected. Complete separation of thorium was obtained by redissolving the first tannin precipitate and repre- cipitating the zirconium as described below. PROCEDURE- Treat the zirconium - thorium chloride solution, which must be free from sulphate, with 20ml. of saturated ammonium chloride ‘solution and neutralise to Congo red with ammonia. Add the calculated quantity of 2 N hydrochloric acid to give a solution which is 0.15 N with respect to the acid when the volume is made up to 200 ml. Heat the solution to boiling, add 1.5 g.of tannin, freshly dissolved in 25 ml. of water, gently boil for a minute, and set aside to settle for 2 hours. Filter through a Whatman No. 42 filter-paper, wash the precipitate on the filter three times with 10 to 15-ml. portions of a solution of 10 per cent. of ammonium chloride in 0.15 N hydrochloric acid. Transfer the precipitate and the filter- paper to the original beaker, add 60 ml. of diluted hydrochloric acid (1 + 1) and boil gently for 15 to 20 minutes. With Congo red as indicator, carefully neutralise the excess acid with diluted ammonia solution (1 + 6) and add 20 ml. of ammonium chloride solution and sufficient 2 N hydrochloric acid to make the aciditj- once again 0.15 N when the solution is diluted to 300 ml. Dilute, boil and add 1.5 g. of freshly prepared tannin solution.Continue boiling for another 2 minutes and set aside for 2 hours. Filter through a Whatman No. 42 filter-paper and wash the precipitate first with a solution of 10 per cent. of ammonium chloride in 0.15 N hydrochloric acid and finally with a 2 per cent. solution of ammonium chloride alone. To determine the thorium, concentrate the combined filtrates to a small volume, add a slight excess of ammonia followed by a further 1 g. of tannin and heat to boiling. Allow the precipitate to settle, filter, and wash it with a solution of 2 per cent. of ammonium chloride; ignite and weigh as Tho,. The results of test separations are given in Table 111. TABLE I11 TEST SEPA~RATIONS ZrOz taken == 0.0550 g. Expt. KO. Tho, added, ZrO, weighed, Tho, found, g. g. €5 1 0.0870 0.0550 0.0860 2 0.0870 0.0547 - 3 0.0870 0.0545 I 4 0.0870 0.0549 - 5 0.1740 0.0548 0.1745 6 0.1740 0.0551 - Set aside in a warm place overnight. Ignite and weigh as ZrO,.October, 19501 RYAX : THE COLORIMETRIC DETERMIKATIOS OF RHODIUM 557 The residual zirconium dioxide from experiments 1 and 6 was fused with potassium The extract was boiled No turbidity appeared even after standing overnight. bisulphate and the melt extracted with 0-5 N hydrochloric acid. with saturated oxalic acid solution. This shows that the zirconium precipitate was free from thorium. REFERENCES 1. 2 . 3. Schoeller, W. R., Analyst, 1944, 69, 259. Kumins, C. -4., -4,tal. Chem., 1947, 19, 376. Osborn, G. H., Analyst, 19-28, 73, 381. ,4SDHRA UNIVERSITY WXLTAIR, S. INDIA February, 1950

ISSN:0003-2654    

DOI:10.1039/AN9507500555

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年代:1950

数据来源: RSC

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October, 19501 RYAX : THE COLORIMETRIC DETERMIXATIOS OF RHODIUM 557 The Colorimetric Determination of Rhodium with 2-Mercapto-4 : 5-Dimethylthiazole BY D. E. RYAN SuxoPsIs-Rhodium is determined by the formation of the rhodium complex (C,H,NSCS),Rh, with 2-mercapto-4 : 5-dimethylthiazole and photometric measurement of the optical density of the resulting coloured solution. Platinum and gold do not interfere; interference by palladium is avoided by addition of dimethylglyoxime and filtration. Iridium, in an amount equivalent to that of rhodium, gives results 10 per cent. high; iridium is readily compensated for, however, if its approximate concentration is known. 1 7 ~ i ~ ~ ~ ~ ~ organic monosulphides have been suggested for the determination of rhodiurn.l92,3,4 In all of these methods other platinum metals cause varying degrees of interference. The colorimetric determination of rhodium with 2-mercaptobenzoxazole,2 while providing a method for determining rhodium in the presence of iridium, requires precipitation to effect the desired colour formation, and also suffers interference from platinum and palladium.In this paper is described a procedure for determining 0-5 to 8 pg. of rhodium per ml. in the presence of platinum, palladium, iridium and gold. The determination is based on the colour produced with 2-mercapto-4 : 5-dimethylthiazole, which has the formula CH,-C--N CHS-C C-SH II I! \s/ The rhodium a possibility of using 2-mercapto-4 : 5-dimethylthiazole as a colorimetric reagent for was suggested previously by Haines and Ryan.3 Acid solutions of rhodium develop .n amber-to-red colour on being heated with 2-mercapto-4 : 5-dimethylthiazole and, when there is an excess of reagent present, the intensity of the colour depends upon the amount of rhodium.EXPERIMENTAL The transmittancy curve for a solution containing 6.5pg. of rhodium per ml. is shown in Fig. 1. The data were obtained with a Spekker absorptiometer used in conjunction with a medium glass spectrograph (constant deviation instrument). All matching on the plate was done visually and monochromatic light from a mercury arc was used for determining wavelengths. Although maximum absorption occurs in the ultra-violet, excellent results can be obtained in the visible spectrum. A Spekker photo-electric absorptiometer, with an Ilford No.601 filter (maximum transmittancy at 430 mp.), was used to obtain the data for the development of the colorimetric method for rhodium. The maximum concentration that could be measured in a 1-00-cm. cell was found to be 8 pg. of rhodium per ml., while a concentration of 0.5 pg. per ml. gave a minimum trans- mittancy of 88 per cent. More or less highly concentrated solutions can be measured when very thin or very thick layers of solution are used.55s RYA?; : THE COLORIMETRIC DETERM1,UATIOS OF RHODIUM [Vol. 75 REAGEXTS- 2-Mercafito-4 : 5-dinzeth_~ZtlziaxoZe-The reagent was obtained from the Eastman Kodak Company and was recrystallised from 25 per cent. ethyl alcohol. A solution was prepared by dissolving 0.5 g. of the recrystallised material in 100 ml. of 50 per cent.ethyl alcohol. This solution was colourless and was stable for several months if kept in a dark bottle; solutions kept in colourless bottles turned yellow within two weeks. 2-Mercapto-4 : 5-dimethylthiazole can be prepared by the method of Buchman, Iiiems and Sa~gent.~ WAVELENGTH. mp Fig. 1. Transmittancy curve for solution containing 6.5 pg. of rhodium per ml. Standard rhodium. solution-Rhodium sponge was converted into the chloride by means of 'concentrated hydrochloric acid and chlorine gas. The resulting solution was evaporated just to dryness and the residue dissolved in a solution containing 1 ml. of concentrated hydrochloric acid per litre. This solution, standardised by both the sulphide6 and mercapto- benzoxazole3 procedures, contained 1-32 mg.of rhodium per ml. Suitable concentrations were prepared by diluting this standard with a solution containing 1 ml. of concentrated hydrochloric acid per litre. PROCEDURE- Measure rhodium samples, either as the chloride or sulphate, into Erlenmeyer flasks, add 10ml. of concentrated hydrochloric acid, and make the volume up to about 40ml. Heat the solutions to boiling, add 2ml. of reagent for each microgram of rhodium per ml. expected, and boil the solutions vigorously for 1 hour. Keep the volume approximately constant by adding distilled water. Cool the samples in running water, make up the volume to 100ml., and measure the optical density with the absorptiometer. The optical densities obtained under various conditions are shown in Table I. These results were obtained with 0.7 pg.of rhodium per ml. using a 4-cm. cell. TABLE I OPTICAL DENSITY OF SOLUTIONS OF 0 . 7 ~ ~ . OF RHODIUM UNDER Condition Optical density VARIOUS CONDITIONS Solutions boiled 46 minutes . . .. .. .. 0.306 Solutions boiled 60 minutes . . .. .. .. 0.319 Solutions boiled 120 minutes . . .. .. .. 0.318 Reagent added, 1.0ml. . . . . .. .. .. 0.292 Reagent added, 1.5ml. . . .. .. .. .. 0.320 Reagent added, 2.0ml. . . . . .. .. .. 0.319 Concentrated HC1 added, 4ml. . . .. .. .. 0-293 Concentrated HC1 added, 8 ml. . . .. .. .. 0.318 Concentrated HC1 added, 15 ml.. . .. .. 1 . 0.319October, 19501 II-ITH 2-MERCAPTO-4 : 5-DIMETHPLTHIAZOLE 559 These data indicate that 2 ml. of 0.5 per cent. reagent solution for each microgram of rhodium per ml. and boiling for 1 hour are necessary for maximum colour development.The optical densities of solutions ranging from 1 to 2 M in hydrochloric acid were the same and no difficulty was encountered in maintaining clear solutions. Extinction - concentration graphs were plotted and showed that the coloured solution obeys Beer's law over the range applicable for a 1.00-cm. cell. The change in optical density on keeping the solutions in daylight in a closed container for 48 hours was less than 3 per cent. COMPOSITION OF COMPLEX The rhodium complex with 2-mercapto-4 : 5-dimethylthiazole was precipitated from a solution 0.1 M in hydrochloric acid. The complex could not be dried at elevated temperatures because it decomposed. The average value obtained for the rhodium content, on analysis of the complex dried in a desiccator over silica gel, was 27.0 per cent.The theoretical value, if two molecules of 2-mercapto-4 : 5-dimethylthiazole are combined with one atom of rhodium, is 26-4 per cent. EFFECT OF VARIOUS ANIONS No interference was noted when 0.5 g. of the sodium, potassium or ammonium salts of the following ions was added to 0.066 mg. of rhodium, as the chloride, and the usual colori- metric procgdure carried out : F', Cl', Bur', C204)', C6H,0,', SOa", C2HS02', POL", CpH,06'. These Nitrate, chlorate and bromate interfere if more than 50 fig. per ml. are present. . V oxidising agents prevent the reduction of Rh"' to Rh" by the reagent urdess a sufficient excess of the latter is present. Complete colour development is possible in solutions containing 500 pg.of these ions per ml. if a suitable excess of reagent is added. Iodide and sulphite ions interfere by producing turbid solutions. Carbonate and cyanide interfere if more than 4Opg. per ml. are present. REACTIONS OF VARIOUS CATIONS Studies of the reaction of various ions under conditions similar to those used for rhodium -in which 5 mg. of the metal ions, as chloride, sulphate, or acetate, were used-showed no colour or precipitate with the following: Fe"', Co", Ni", Pb", Zn", Sn", Sn"", Al"', Sb"', Ba", Be", Ca", Mg", Mn", Ti"", UO,", Cd", K' and Na'. Furthermore, about 5 mg. of tungsten (as sodium tungstate), molybdenum (as ammonium molybdate) and arsenic (as potassium arsenate) gave no noticeable reaction. The cupric ion gave a yellow precipitate and bismuth gave a solution coloured a faint yellow. The mercuric ion gave no reaction under the acid conditions used for the rhodium determination, but reacted to give a white precipitate in neutral medium. Silver gave a yellow precipitate on addition of the reagent to an aqueous solution of silver nitrate.Chromate was reduced to tervalent chromium, the solution becoming pale green in colour. Of particular interest, however, are the reactions of gold, platinum, palladium and iridium, as these elements are usually associated with rhodium. Gold (AuC1,') solutions gave an immediate white precipitate. Gold, in solutions treated in the same manner as for rhodium, was completely precipitated. Filtrates from solutions containing 15 pg. of gold per ml. were colourless and showed no difference from the blank when checked in the absorptiometer.Platinum (PtC16") solutions reacted to give a yellow solution or precipitate depending on the platinum concentration, but platinum, in solutions treated in the same manner as for rhodium, was completely precipitated. Filtrates from solutions containing 3 pg. of platinum per ml. were colourless and showed no difference from the blank when checked in the absorptiometer. Palladium (PdCI,") solutions gave an amber-to-red colour similar to that given by rhodium. Solutions containing even as little as 0-3 pg. of palladium per ml. gave a colour noticeably different from the blank ; palladium must therefore be removed before determining rhodium. The very dark red iridium (IrC16") solutions were changed in colour to a very pale olive- green.Solutions treated in the same manner as for rhodium, however, developed a more intense greenish-yellow colour and 3.5 pg. of iridium per ml. gave an optical density equivalent to 0.4 pug. of rhodium per ml.560 RYAN THE COLORIMETRIC DEtTERMIXATIOX OF RHODIUM [Vol. 75 THE DETERMINATION OF RHODIUM WHEN OTHER PLATINUM METALS ARE PRESENT PLATINUM AND GOLD- Since platinum and gold are precipitated by 2-mercapto-4 : 5-dimethylthiazole to yield colourless filtrates, the following procedure allows the direct determination of rhodium in the presence of these elements. Procedure-Treat solutions 3s previously described for rhodium but add 2 ml. of reagent in excess of that necessary for rhodium. Cool the solutions in running water for 20 minutes, dilute to about 70 ml.and filter off the precipitates. Wash the precipitates once with 5 ml. of cold water, make up the filtrate to 100 ml., and measure the optical density. Typical results are shown in Table 11. TABLE I1 DETERMINATION OF RHODIUM IN PRESENCE OF IRIDIUM, PALLADIUM, PLATINUM OR GOLD Rh present, pg. per ml. 0.7 0-7 3.3 6.6 1.3 6-6 0.7 3.3 6.6 6.6 6-6 0.7 0.7 6.6 6.6 6-6 6-6 6.6 6-6 Rh found, pg. per ml. 0.7 0.8 3.7 7 . 3 1.3 6.6 0.7 3.4 6.7 6.5 8.4 Other metal pg. per ml. 0-7 I r 1.3 Ir 1, 3.5 Ir >, 6.0 Ir 3.5 I r 6.0 I r 91 present, Remarks i r not allowed for in blank 11 Ir compensated in blank 5.0 Pd 8.4 Pd 7, 17.0 Pd* 7 3 34-0 Pd 7? Pd first separated by dimethylglyoxime 3.0 Pd Pd not separated 0-7 3.0 Pt Pt precipitated by reagent and filtered 0-7 6.0 Pt 11 6.6 3.0 Pt 7) 6-5 12.0 Pt 19 6.6 15.0 Pt* 71 6.5 17.0 AU precipitated by reagent and filtered 6.6 15.0 Au* I f 6.6 34.0 AU l* * These results were obtained independently by a member of this laboratory. The blank, except where stated for iridium, was distilled water.PALLADIUM- This is accomplished by precipitating the palladium with dimethylglyoxime and determining rhodium directly in the filtrate from the palladium determination. Procedwe-Add 1 ml. of a 1 per cent. alcoholic solution of dimethylglyoxime to 50 ml. of a solution containing approximately 0.7 ml. of concentrated hydrochloric acid. Allow the solution to stand for 1 hour and filter through a porcelain crucible with a porous bottom. Wash the precipitate three times with 5-ml.portions of hot water, add 10 ml. of concentrated hydrochloric acid to the filtrate, and carry out. the regular procedure for rhodium. Typical results are shown in Table 11. Palladium must be removed before determining rhodium. IRIDIUM- are about 10 per cent. high. of 3-5 pg. of iridium per ml., the rhodium found was 3-7 pg, is known, however, its interference can readily be compensated for. in Table 11. Iridium, when present in an amount equivalent to that of rhodium, gives results that When 3.3 pg. of rhodium per ml. was determined in the presence If the amount of iridium present Some results are shownOctober, 19501 NOTES 561 The author thanks Mr. L. S. Theobald, in whose laboratory this research was carried out, for his encouragement and help in this work. Thanks are also due to W. P. Doyle for his help in obtaining the transmittancy data, and to Miss M. E. Dalziel for determining rhodium in various platinum metal solutions by the dimethylthiazole procedure. The author wishes to record his sincere appreciation to Lord Beaverbrook for providing the scholarship, through the Beaverbrook Overseas Scholarship Fund, which enabled this work to be completed. REFERENCES 1. 2 . 3. 4. 5. 6. Currah, J. B., McBryde, I\-. A. E., Cruikshank, A. J., and Beainish, F. E., I d . Eng. Clzem., Aiznl. Ryan, D. E., Anal. Ciieiiz., 1950, 22, 599. Haines, R. L., and Ryan, 1). E., Cmad. .J. Res., 1949, B, 27, 72. Ubaldini, I., and Sebbia, L., Awn. Chint. rlppl., 1948, 38, 241. Buchman, E. R., Kienis, A. O., and Sargent, H. J., .J. Org. Chem., 1941, 6, 764. Gilchrist, R., and Wichers, E., J . Airier. Chew. SOC., 1936, 57, 2565. Ed., 1946, 18, 120. DEPARTMEXT OF CHEMISTRY IMPERIAL COLLEGE OF SCIENCE AND TECHNOLOGY I,OKDON, s.13'.7 March, 1950

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DOI:10.1039/AN9507500557

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年代:1950

数据来源: RSC

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October, 19501 NOTES 561 Notes THE MICRO-K JELDAHL DETERMINATION OF SERUM PROTEINS, WITH SELENIUM AND COPPER AS CATALYSTS: IKTERRELATION OF TIME OF DIGESTIOPIT AND COXSTITUENTS OF THE DIGESTION MIXTURE IN the micro-Kjeldahl determination of protein, a consideration of such factors as the digestion time and the amount of salt and catalyst shows that they are not independent. We have investi- gated the interrelationship of these factors as applied particularly to serum proteins by using a combination of selenium dioxide and copper sulphate as catalysts, and have also determined the optimum conditions for the complete recovery of nitrogen. In all the experiments, 0.1 ml. of serum was used with 1 ml. of sulphuri'c acid, the copper sulphate being added as a saturated solution and the selenium dioxide (in aqueous solution) introduced after the contents of the flask were charred.Heating during the digestion was carried out in such a way that the acid vapours just condensed in the lower part of the neck of the flask, the upper part being barely warm to the touch. Experiments have shown that unless these con- ditions of heating are carefully adhered to the recovery of nitrogen will be low. The ammonia distillation apparatus was similar to that of Markham.l The distillate was received in boric acid solution and titrated with standard sulphuric acid using Tashiro's indicator. As the nitrogen content of the serum used was unknown, the analyses were invariably made in replicate (never less than in duplicate). All of the mean results that fell within four times the standard error, that is within 4 x 0*01/1/2 of the maximum mean titre were taken as indicating complete recovery.The term 0.01 represents the standard deviation of the titres obtained under our optimuni conditions of digestion. ,411 the results were then expressed as percentages of these maximum titres; the spread of the maximum recovery being 99.9 to 100.2 per cent. TABLE I The results were analysed statistically. \'ARIATION OF RECOl'ERY O F NITROGEN WITH AMOUST OF SODIUM SULPHATE AND TIME OF DIGESTION 20 mg. of copper sulphate and 0.36 mg. of selenium in each digestion Amounts of Na,SO, (g. to 1 ml. of H,SO,) 0.08 0-40 1.0 A r 7 Recover\- o f nitrogen Tiiiic of digestion ------7 0 70 a / 0 ' 10 30 niinutes . . . . .. . . 91-5 (37.0 98.3 1 hour .. . . . . . . 93.3 98.2 100.0 3 99 . . . . .. . . 94-7 99.0 100.0 3 " .. . . . . . . 97.0 99.5 100.0 4 > 9 . . . . . - . . 97.8 99.9 100.2 8 9 - .. .. .. . . 100.2 99.6 100.1 14 " .. . . . . . . 99.8 (39.9 99.2562 NOTES [id. 75 TABLE I1 \--\RIATION OF RECOVERY OF XITKOGEN WITH AMOUNT OF SELENIUM ASD S O T ) I ~ M SULPH-~TE Amount of Sa,SO, (g. to 1 ml. of H,SO,) Amount of Se, ing. nil nil 0.35 1.75 3.5 3.6 7.0 14-0 38.0 V R T I 0 I 0.16 0.40 1.0 1.0 I hour 1 hour 1 hour 30 miu. digestion digcstion digestion digestiun Amount of fng. nil 20 20 20 nil 20 20 20 20 CUSO,, I liccowrj- df nitrogen ----.-.---------0,' . o 0' , 0 01 /O _- 97.9 I 97.0 99.G 95.3 98.2 100.1 - 99.2 99.9 - - 99.0 97.5 99.0 100.2 98-2 99.2 - - 99.3 100.1 - 99.3 99.9 - TABLE I11 r OF RECOVERY OF NITROGEN WITH AMOUR'T OF SELENIUM AXD TIME O F l3IGESTION 20 mg.of copper sulphate and 1 g. of sodium sulphate in each digestion Amount of Se, mg. nil 0.35 3.5 Digestion Recovery of nitrogen time, -l 0.6 97-6 98-3 99.2 1 99.6 99.9 100.0 4 100.0 100.1 99-7 14 98.6 99.2 96.4 21 97.8 96.6 94.3 hours Yo 0'" % From the tables it would appear that for a digestion time of 1 hour the optimum conditions for complete recovery of nitrogen from 0.1 ml. of serum are the presence of sodium sulphate to the amount of 1.0 g. to 1 ml. of sulphuric acid, and the addition of 3.5 mg. of selenium and 20 mg. copper sulphate as catalysts. Since lysine is amongst the most refractory of the amino acids in serum proteins, the nitrogen was estimated in a specially pure specimen of lysint: mono-hydrochloride under the above conditions.Although the method gave a practically theoretid recovery (99.3 per cent.) this result was only attained when 0.5mg. samples were used. The recommended method was then compared with the recently described procedure of Hiller, Plazin and Van Slyke,2 which was shown to be equal to the classical Dumas method. Total nitrogen was estimated in 0-1-ml. amounts of two different sera and the results are shown in Table IV. COMPARISON OF PROPOSED METHOD WITH THAT OF HILLER et al. (1948) !Proposed method Method of Hiller2 Nitrogen, S i t rogen , mg. "g . SERUM A Mean .. .. .. .. 1.291 (5) 1.289 (G) Range . . .. .. . , 1.287 to 1.296 1.287 to 1-293 Standard deviation . . .. & 0.0022 f 0.0024 SERUM B Mean .... .. .. 1.316 (6) 1.315 (G) Range . . .. .. . . 1.323 to 1.321 1.313 to 1.319 Standard deviation . . .. f0.0030 * 0*0022October, 19501 NOTES 563 DISCUSSION OF RESULTS Certain conclusions can be drawn from these experiments, although as we have confined our- selves to serum proteins, these conclusions may not be applicable to other nitrogen compounds. The results indicate that for maximum recovery of nitrogen, the time of digestion and the amount of sodium sulphate are inversely related; a long period of digestion with a small proportion of the salt will give 100 per cent. recovery of nitrogen just as will a much shorter period with a greater proportion. Other things being equal, it is clearly preferable to use the shortest digestion time consistent with maximum nitrogen recovery and this involves the use of a relatively high proportion of the salt.Too high a proportion, however, may necessitate careful attention t o heating so as to avoid loss of acid. Further, the effect of the selenium catalyst is less, at any rate for serum proteins, when the higher proportions of sulphate are used, and hence the use of large amounts of seleniuni would appear from our results to be unnecessary. It does not appear possible, moreover, to compensate completely for a low proportion of sodium sulphate by increasing the amount of selenium, that is, with a low proportion of the salt, the time of digestion must be longer, and this time is not greatly reduced by increasing the amount of selenium. In protracted digestion, the presence of selenium tends to increase the losses of nitrogen-possibly bv increasing the oxidation of ammonia.Although it was not our purpose to compare the relative efficacy of different catalysts in the niicro-Kjeldahl procedure, the statement by Hiller et aZ.2 that only digestion mixtures containing niercury as catalyst have been found to give nitrogen values as high as those yielded by the Dumas combustion method must be modified in the light of our results. This investigation shows that a method using selenium and copper sulphate catalysts gives results that are in every way com- parable with the results obtained by their method using mercury. SUMMARY The relationship between time of digestion, amount of sodium sulphate and of selenium as catalyst in the micro-Kjeldahl determination of serum proteins has been investigated. The optimum conditions for 0.1 ml. of serum are shown to be 3.5 mg. of selenium, 20 mg. of copper sulphate, 1 g. of sodium sulphate and 1 ml. of sulphuric acid for a digestion time of 1 hour. This method and that of Hiller et aZ.2 have been compared and shown t o be equally accurate. The above work forms part of a larger investigation on the serum protein levels of infants by B. Levin, Helen M. Mackay (member of the scientific staff of the Medical Research Council) and Catherine A. Neill, with the assistance of V. G. Oberholzer and T. P. Whitehead, who gratefully acknowledge grants from the Medical Research Council. REFEREXCES 1. Markham, R., BLoclre:i/. J . , 1942, 36, 790. 2 . Hiller, A., Plazin, J., and Van Slyke, D. D., J . Bid. C h e ~ i . , 1948, 176, 1401. THE QUEEN ELIZABETH HOSPITAL FOR CHILDREN LONDON, E.2 B. LEVIN V. G. OBERHOLZER T. P. WHITEHEAD First submitted, February, 1950 Amended, June, 1950

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564 OFFICIAL APPOISTMENTS [Val. i 5 Ministry of Food STATUTORY INSTRUMENTS* 1950-No. 1313. The Flour (Amendment No. 3) Order, 1950. Price Id. This Order, which amends the Flour Order, 1947, as amended, provides f o v the rate of extractiolt oj iintaonal pour to be reduced fyoni 85 per c<mt. to 81 per cevt. on Augzrst 27th, 1960, and of " Ti;'' f l o w .frow over 85 per cent. to over 81 per cent. f v o m the saiize date. CIRCULAR. MF 15/50 This civculair, dated 16th _-fugidst, 1950, contains ,the information that, as a vesult of the decision irt the K i ~ g ' s Beiich Division i~ the case of Kat zl. Divzent, thi: AIinistiy of Food Code of Pvactice relatiug to T/vincgnv and Solutioti of Acetic Acid, printed at p . 55 of '' The cidvertising, Lnbellirag & Conipositiou of Food" (H..11. Staiionery Ofice, 1949) has beeM withdi,nw'r?. * Obtainable froin H.M. Stationery Office. Italilx indicates changed wording.

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October, 19501 REVIEWS 565 Reviews RADIOACTIVE INDICATORS. THEIR APPLICATION IN BIOCHEMISTRY, ANIMAL PHYSIOLOGY AND PATHOLOGY. By GEORGE HEVESY. Pp. xvi + 556. London: Interscience Publishers Ltd. 1948. Price 60s. net. The possibility of using radioactive isotopes as indicators in biological systems was first demonstrated by Professor Hevesy more than 25 years ago. In a celebrated paper published in the Biochemical Journal in 1923, he described “the absorption and translocation” by plants of thorium B, a naturally-occurring radioactive isotope of lead. Although no further tracer experi- ments could be undertaken until after the discovery of deuterium and the invention of the cyclotron 10 years later, the concepts introduced by Hevesy in his original investigation have been accepted as the basis of modern tracer techniques.In the words of Professor Rittenberg, Hevesy “was not only one of the fathers of the isotope technique, but also the attending gynaecologist.” His contributions to the subject have been recognised by the award of a Nobel Prize in 1943 and a Faraday Medal a few weeks ago. Such is the reputation of the author of this monumental volume 011 the application of radioactive isotopes in animal physiology, pathology and biochemistry. Although applications in plant physiology and all references to stable isotopes have been omitted, this book provides the most comprehensive review of the isotope technique that has yet appeared. While writing the book, Hevesy was resident in turn at the Universities of Copenhagen, Stockholm and California, and he is thus able to appraise both European and American work. Although the book was printed in the United States, the European system of indicating atomic mass by a raised prefix (e.g., 14C) rather than a raised suffix has been adopted.The first three chapters describe the production and measurement of radioactive isotopes and include a list of the isotopes that were available from the United States Atomic Energy Com- mission in September, 1947. In future editions it should be mentioned that most of these isotopes can be supplied by the British Atomic Energy Research Establishment. Sub- sequent chapters deal with the measurement of the absorption, distribution and excretion of elements, phase boundary permeability and turnover-time. Although for certain specialised aspects of the subject the treatment is neither as up-to-date nor as detailed as that given in special monographs, such as Calvin’s “Isotopic Carbon” (see Analyst, 1950, 75, 113), the volume is fully up to the standard to be expected from Professor Hevesy.I t should be in the hands of all persons who are either proposing to use radioactive isotopes in biological studies or are interested in the important results obtained by their means. The applications of isotopes in chemical analysis are described in one short chapter. J. E. PAGE HIGH POLYMERIC CHEMISTRY. By UT. S. PENN, B.Sc. Pp. xvi 3- 487. London: Chapman & The purpose of this book is to describe the theories that govern the formation and properties of high polymers, and to stress throughout the chemical point of view.Although not neglected, less emphasis is paid to the practical aspects of the question. The subjects dealt with include the mechanisms whereby large polymer molecules are formed and methods of following the reactions involved, hydrocarbon substituted polymers and vinyl polymers, polydienes from hydrocarbons and halogenated hydrocarbons, condensation resins, resins from natural products, proteins and thermosetting resins. Errors and spelling mistakes and misprints in formulae are relatively few and in most cases the true meaning is obvious from the text. There are, however, a few points to which attention should be drawn. It might be useful in future editions to give, throughout the book, the original sources of information about the properties of the polymers that are shown in tabular form.On p. 77 it should be pointed out that the determination of the iodine number by the Wijs’ method involves the titration of the iodine liberated by a known volume of the Wijs’ reagent itself. The section on “Analytical Schemes” on p. 95 might be improved considerably. It is suggested on p. 96 that by following the procedure given in 1& pages of text it should be possible to ascertain exactly the nature of any high polymeric material; this statement is quite misleading. On p. 296 it is difficult to see exactly how conductivity cells are to be used in the determination of viscosity. Hall Ltd. 1949. Price 36s. net. There is a useful chapter on the preparation of monomers.566 REVIEWS [VOI.75 The author of this book hopes that the treatise may be accepted as a standard textbook, and although it may be doubtful whether this desire will be realised, there is no doubt that he has brought together a very great deal of information about the various theories underlying the structure and formation of polymers. To young chemists entering this field the book is likely to be extremely useful because of the comprehensive character of the references t o original papers on the subject. J. HASLAM A CHEMISTRY OF PLASTICS AND HIGH POLYMERS. By PATRICK D. RITCHIE. Pp. viii +- 288. London : Cleaver-Hume Press Ltd. New York : Interscience Publishers Inc. 1949. Price 25s. This book is concerned primarily with the organic chemistry of high polymers and it has very little to tell of their applications, testing or analysis. Because of the wide differences in character between high polymers the book falls into distinct sections, dealing with (a) synthetic plastics, (bj natural products such as proteins and cellulose, and (c) a number of inorganic materials such as graphite, and zeolites and other silicates. There is also a short review of the relation between the structures of high polymers and their physicd properties. The identity of the various materials and the reactions by which they are prepared are clearly described. The book will provide a readable and useful guide t o degree students, for whom it was chiefly designed. G. H. WYATT

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566 REVIEWS [VOI. 75 Publications Received THE PHARMACOPOEIA OF THE UNITED STATES OF AMERICA. New York: Mack CELLULOSE ACETATE PLASTICS. By VIVIAN STANNETT. Pp. xxiv + 325. London: Temple PHYSICO-CHEMICAL CONSTANTS OF PURE ORGANICOMPOUNDS. By J. TIMMERMANS. Pp, viii -,- London: Cleaver- THE CHEMISTRY OF INDUSTRIAL TOXICOLOGY. By H. B. ELKINS. Pp. ix + 406. London: Pp. lv + 1067. Publishing Co. 1950. Price $9.00. Press, Ltd. 1950. Price 30s. net. 693. Hume Press, Ltd. 1950. Price 95s. net. Chapman & Hall, Ltd. New York: J. Wiley & Sons, Ltd. 1950. Price 44s.; $5.50. Objectives Sub-committee Surveys Report No. 24. London : H.M. Stationery Office. 1950. Price 3s. 6d. Pp. xiv -+ 357. New York and London: Interscience Publishers, Inc. 1950. Price 56s. By L. H. CURTMAN, Pp.vii $- 391. London and Nt:w York: Macmillan & Co., Ltd. 1950. Price 28s. 6d. Pp. xx -+ 856. London: Leonard Hill, Ltd. 1950. Price 37s. 6d. & Hall, Ltd. New York: J. Wley & Sons, Ltd. 1950. Price 40s.; $5.00. Price 35s. HANS LIEB and WOLFGAKG SCH~NIGER. Pp. xi + 158. Vienna: Springer-Verlag. 1990. Price 18s. New York and Amsterdam: Elsevier Publishing Company, Inc. THE PHARMACEUTICAL INDUSTRY IN GERMANY DURING THE PERIOD 1939-1 945. British Intelligence Pp. 120. MELTING AND SOLIDIFICATION O F FATS AND FATTY ACIDS. INTRODUCTION TO SEMI-MICRO QUALITATIVE CHEMICAL ANALYSIS. By A. E. BAILEY. Revised Edition. ,4 DICTIONARY OF DAIRYING, By J. G. DAVIS, I>.Sc., Ph.D. (Lond.), F.R.I.C. QUANTITATIVE ULTRAMICROANALYSIS. By P. L. KIRK, Ph.D. Pp. Vii + 310. London: Chapman BIOLOGICAL STANDARDISATION. By J. H. BURN. London: Oxford University Press. 1950. ANLEITUNG ZUR DARSTELLUNG ORGANISCHER PRAPARATE MIT KLEINEN SUBSTANZMENGEN. By

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