摘要:

2534 TYRER : ADIABATIC AND ISOTHERMAL COMPRESSIBILITIES OFCCXXXV1.-Adiabatic and Isothe~~mal Compresstbilztiesof Liquids between One and Two Atmospheres'P rc'ssure.By DANIEL TYRER.THE present paper constitutes an extension of a previous one (T.,1913, 103, 1675) on the compressibility of liquids, in which a newand precise method for the determination of compressibilities atlow pressures was described.Since the publication of the previous results, i t was discoyeredthatt a small correction to the observed values had been overlooked.This was due to neglecting the small change in pressure on theliquid caused by the change of level of the liquid in the verticalcapillary tube (see the previous paper). Although this pressure isvery small compared with the total external pressure change, itintroduces a correction greater than the general experimental error,and must therefore be taken into account.Fortunately, thiscorrection can be accurately calculated from the observed data,and, on the average, causes the results to be raised by about 0.5per cent. All the previously obtained results have accordinglybeen corrected, and the corrected values are contained in the tablesin this paper. The necessity of this correction is to be regardedas a disadvantage of the piezometer. It has also been noticed thatfor rather viscous liquids, such as aniline, the capillary tuberequires a long time to drain, and for easily vaporised liquids,such as ether, slight errors are introduced by the evaporation ofa little liquid in the capillary tube during an experiment.Toavoid these disadvantages and sources of error, the piezometer wasmodified, as is fully described below. In order to test the1 accuracyof the previous resulta (corrected as explained above), a few ofthe determinations were repeated, in each case with the new piezo-meter. As will be seen from the following tables, the differencesbetween the old and new results are, in general, very small, whichgives considerable confidence in the validity and precision of themethod.In order to determine the isothermal compressibility from theadiabatic value, use is made of the following thermodynamicequation :P = a + ~(2y.Jb c,where p and a are the isothermal and adiabatic compressibilitieLIQUIDS BETWEEN ONE AND TWO ATMOSPHERES’ PRESSURE.2535respectively, v the specific volume, J the mechanical equivalent ofheat, C, the specific heat a t constant pressure, and T is theabsolute temperature.I n the previous work, in order to obtain values of dv/dt and ofC,, the results of other investigators were relied on. I n the caseof C,, errors, even moderately large, have a comparatively smalleffect on the accuracy of 8, but in the case of dvldt the effect oferrors is considerable. It was found that in many cases the valuesof dv/dt which had been calculated from the specific-volume dataof various investigators contained considerable errors, and i t wastherefore necessary to make a series of accurate specific-volumedeterminations for each liquid, from which accurate values ofdv/dt could be calculated.The practical part of the work istherefore divided into two parts, namely, tlie determination ofadiabatic compressibilities a t different temperatures and the deter-mination of specific volumes.,4ppratus: The New Form of Pieaometer.The construction of the piezometer can best be understood byreferring to the diagram. The liquid to be investigated is con-tained in the inner vessel, A , of ordinary soda-glass, filled com-pletely up to and between the two taps, T and T,, and the mercurythread in the horizontal capillary tube, B. The two tubes C andD are attached by stout rubber tubing to a small air-pump andmanometer. On increasing the pressure, the mercury thread isdepressed in the graduated tube, B.When the temperature isconstant, the pressure is released, and the-change in position ofthe mercury thread in B is noted. The filling of the piezometeris effected by first exhausting i t of air, by attaching the sidetubeE to a strong pump, and then allowing the liquid to enter throughthe tap T. When almost filled, the capillary tube B is dried, themercury thread allowed to enter, and then the last few C.C. of airexpelled from the apparatus by warming. It is emptied by invert-ing the instrument and attaching the tube E t o a suitable ex-hausted receptacle.For further details of the rest of apparatus, and the manner ofworking, the previous paper must be consulted. No correctionbeyond that of the compressibility of the glass is necessary.Forthe compressibility of the glass, the result of Amagat (2.18 x 10-6)has been taken as correct.The volume of the piezoniebr used was about 450 c.c., and thediameter of the graduated capillary tube depended on the com-pressibility of the liquid in the apparatus, but was such as t o giv2536 TYRER : ADIABATlC AND ISOTHERMAT, COMPRESSTBILITIES OFa change of reading of about 6 to 10 cm. for a pressure change ofabout one atmosphere.The average error of the adiabatic compressibility determinationsdoes not appear to bo greater than 0-1 per cent. Probably thegreatest constant error lies in the correction for the compressibilityof the glass, but this must be comparatively small, f o r it was shownin the previous communication t h a t results obtained with a copperpiezometer, which requires a much smaller correction than glass,are in good agreement with the results obtained with a glasspiezometer.Determination of Values of dvldt.I n order to be able to calculate accurate values for the functiondv/dt, very accurate specific-volume data-carried out, to the fifthdecimal place a t least-are necessary.The dilatoineter is notcapable of giving such a degree of accuracy, and hence tlie longermethod of the pyknometer had t o be used. The ordinary SprengeLIQUIDS BETWEEN ONE AND TWO ATMOSPHERES' PRESSURE. 2537form of pyknometer is liable to considerable error for volatileliquids, owing to evaporation in the two capillary tubes, and forviscous liquids there is always an appreciable quantity of liquidwhich clings to the sides of the unfilled part of the capillary taube.A new form of pyknometer was therefore devised which has onlyone capillary tube instead of two.On the capillary tube is etcheda fine mark, and tho open end is widened out and provided witha ground-glass stopper. The instrument had an approximatevolume of 70 C.C. The empty part of the instrument above themark on the capillary tube can be thoroughly freed of adheringliquid. The filling and emptying of the pyknomet'er is effected byattaching to i t a small dropping funnel provided with a side-tubeand tap, through which the instrument is exhausted. The liquidis then run in, and fills the pyknometer completely. The liquiddoes not come into contact with any rubber connexions during thefilling, and is always kept in contact with dry air only.The fill-ing under exhaustion also serves to free the liquid from dissolvedair.As the capillary stem of the instrument may be made to anydegree of fineness, the adjustment of the volume may be made t oa very superlative degree of accuracy. The weighing of the pykno-meter was made to 0.1 milligram, and all weights were reduced toa vacuum. The thermostat used consisted of a large 40-litre water-bath provided with a motor-driven stirrer and a thermoregulator ;the temperature remained constant to less than O*0lo. It may besaid, therefore, that practically all error lay in the temperaturereading. For this purpose, a series of finely graduated thermo-meters was used, capable of being read with accuracy t o less thanO*0lo, which had been standardised by comparison with the normalhydrogen thermometer.I n addition, they were compared withanother set of thermometers, and the fixed points (melting andboiling points) were tested, and the melting point of sodiumsulphate (Na,S0,,10H20, 32.38O : Richards and Wells, Zeitsch.plhiysikal. Chem., 1890, 26, 690) was carefully determined. A t nopoint was the correction greater than 0'02O. The error of tempera-ture readings was probably not, on the average, greater than O*0lo.Now for liquids the value of duidt of which is less than 0.001,an error in the temperature reading of O*0lo causes an error in thespecific volume for a liquid of average density which affects thesixth decimal place only.Hence it is reasonable and logical t ocalculate the specific volumes to six decimal places. A t the highertemperatures the degree of accuracy would be rather less than this,on account of 3 somewhat greater temperature error2538 TYRER : ADIABATIC AND ISOTHERMAL COMPRESSIBTLITIES OFThe volume of the pyknometer was accurately determined a tdifferent temperatures by weighing it filled with boiled, distilledwater. These calibrations were also repeated, using distilledmercury in place of the water.* The calibrations were repeated a tvarious times to see whether the volume of the pyknometer wasakering with time, but no change was observed.The Pure Liquids.They were generallyfractionally distilled or frozen, and, where possible, they were driedover phosphoric oxide.The fractionation was continued until aliquid of constant boiling point was obtained, and the density wasunchanged by further distillation. I n the following table aregiven the constants (boiling points and densities a t 0.) of the pureliquids used, where thaw had come within the scope of accuratemeasurement. (Only boiling points below looo were accuratelymeasured.) The corrections of the boiling points to normalpressure were made by calculating the values of d t / d p from theClapeyron-Clausius latent heat relation, which is a much moresatisfactory method than the use of tables of experimental valuesof dt f d p , a function extremely difficult to measure with accuracy.All the liquids used were highly purified.Liquid.Carbon disulphide.........Ethyl acetate.. .............Ethylene chloride .........Chloroform ..................Toluene .....................Aniline ........................Nitro benzene ...............wXylene .....................Ethyl bromide ............Ethyl iodide ...............Benzene .....................Ether ........................Methyl alcohol ............Ethyl alcohol ...............Chlorobenzene ............Density at 0".1.293040.924681-282481 -52 0490.884121.038931.20323 at 20"0.881 5 11.498211.980380.88946 at 10"0.736390.810400.806451- 12780Boiling pointat 760 mm.46-26'77-1583.4561.21 --38-4072-5280.2834.6064.7278.32IAdiabatic Compressibilities and Specific Volumes.I n the following tables are given for each liquid the experi-mental results of the adiabatic compressibilities. For the liquidswhich had been previously investigated, the values corrected, asexplained in the introduction, are given, together with a few* The specific volumes of water given by Thiesen, Schecl, and Diesselhorst(Landolt-l3ornstein, " Tabellen ") were used, and for mercury the results of Chappuis(ibid. )LIQUIDS BETWEEN ONE AND TWO ATMOSPHERES' PRESSURE.2539supplementary values obtained by me'ans of the new form of piezo-meter.For each liquid, also, the experimental specific-volume data aregiven, together with the constants in the' equation Vt= 7, + at + bt2.It was exceedingly laborious to find an equation containing fourterms on the right-hand side to fit the experimental results for thewhole temperature range, and it was better to find two equationsof three terms each covering a range of not more than 40°.I n the following table, to expresses the temperature in degreescentigrade, a is the adiabatic compressibility, and v the specificvolume.Carbon Disulphide.to.0.012.7712-5820.3029-2 133.3940.0519.8327.1834-02to.0.014.1420.9629-4236-7744.8054-310.09.3 124.3135.2049-89a x 10'.to. V.Old rt sults corrected.52.95 0.0 0.77337057.94 11.66 0.78385757.74 16.97 0.788 7 6860.61 23.74 0.79515463.9 1 30.72 0*80188865.49 39.07 0.8 1 0 14469.13New results.60.4363.3566.36VZ 0.7733 70 + 0.00088 18 t f 0.05 15 10 L'.(7hloro f orm.a x 10".Old results corrected.59-3065.9 168.9974.0078-2083.1 190.6558.5462-6570.7577.3587.25New results.to.0.010.3 115.9425-0732-0640.3547.4054.60?'.0.6550970.6634080.6681310-6759420.6820880-68 96440.6962780.703199~t=0.655097+0.0,79260 1+0-0,1576 L'.(0-30").~t=0*680294 +0~~~88323(~-30)+0~051945(t-30)'J. (30"-60")2540 TYRER : ADIABATIC AND ISOTHERMAL COMPRESSIBILITIES OFToluene.to.12.4216.0127.1038.7450.2660.1668-5684.1 10.012-4147.1057-7267.6090.002 1.5036.4329-4247.27a x 108.Old results corrected.Glass piezometer.64.1965.8571.1677-3283.8190.8497-32Copper piezometer.109.858-7464.1082.1089.0096.88115.3New results.68.0076.0572-1182.46to.0.014.9821.1725.7830.7440.0050.1373-0579.7379.2499.172'.1-13 10651.1488601.162369191686891.1686891.18072 11-19 1481.224941.235291,234431.26660Z J ~ = 1.131065 + 0.001 1630 t + 0*051959 I '.l't= 1.19131 + 0.0013918 (t - 50') + 0.052834 (1.-_ 50')).(0-40').Benzene.1'.9.5520.3830.5236-3842.7649.5449.6765-4016.1521.9131-334 1.3050-2962.9715.9632.0354-5864.00a x lo6.Old results corrected.Glass piezometer.61.4066-7672.3575-6479.8084-9284.6297.5863-9967.8672.8 I79-4285.5995.20New results.04.1673.2488-5696.45Copper piezometer.2'.11.9214.4017-9024-4247.9558-3362.3072.06T.1.126871.130231.135061.144021.178221.194021.200251.21589~ l t = 1.124278 +0~0013508(t- 10)+0*O5l860(t- 10)".t't= 1-1 8129 + 0*0015038(t - 50) + O*O53086(t - 50)'.[5&80°]LIQUIDS BETWEEN ONE AND TWO ATMOSFHEREY' PRESSURE. 254 1Ether.LO.0.011.1915.5425.3030.6914.6321.1127.6210.9118.5424.9329.50to.0.015-5228-4135-2843.6461.9062-0672.310.012.6417.8227.5039.6252-6560.0272.50a x 10". to.114.3 0.0129.4 13.29139.6 23.90149-5 28-00158.3Copper piezometer.134.5142-8151.3New resulfs.128.24138.62149.05167.73Old results corrected. .Glass piezometer.t't = 1.35793 + 0.0020514t + O*O5542t2.Ethyl Alcohol.a x lo6.Old results corrected.83.9294.45102.04105.99112.36118.9128-5139.6New results.83.8191.3794-22100-7109.31120.05126-69139.95to.0.014-2123.9839.1646.3254.0162-7172-072'.1.357 931-386151.410041.419632.'.1.2399981.2586981.2720431.2936901.304591.3 16381.330471.346311.239998 + 0.0012909S + 0.0,1767t2.q't= 1.29494 f 0.0014749(/ - 40) + 0*053958(t - 40).[40-'70°].VOL. cv2542 TYRER : ADIABATIC AND ISOTHERMAL COMPRESSIBILITIES OFCarbon Tetrac?doride.to. a x loti. to.Old results corrected.Glam piezometer.0.0 63.38 0:012-43 69.33 ' 37-4120-77 73-24 37.9029.09 78-38 46-8938.29 83-88 53.7647-10 90.70 62.6367.72 99.28 72-4367.63 106.7416.16 70.7238-69 84.2360.10 101.650.0 63.0416.27 71.2524.08 75.5438-97 84-8246.85 89-3053.25 95.68Copper piezometer.27-10 76-98New results.t+ = 0.612869 t 0*0:371724f + 0*051227t2.~t=0*643530+0*0,~81438(t- 40)+0*051507(t - 40)'.[40-70'1.U.0.6128690.6257280-6418150.6492430.6560210.6627 150-67 1525Chlorob enzene.to. a x 106. to.Old remlts corrected.0.0 49.19 0.013.40 54.04 24-3224.24 57.54 38.8935.63 61.83 47-9443.97 65.37 60.6352.79 69-59 73.5462-02 74.3671.67 78.8780.47 83-30.0 49-3823-78 57.3941.26 64.09New results.V t = 0.886685 t 0.0384104t + 0*0,9506tS.t*t=0*921848+0.0391697(t - 40)+0*051265(t -7'.0.8866850.9077010.9208300.9293360-9416350- 96428240)'. [40-80°].Methyl -41cohol.to.a x lo6- to.0- 0 88-94 0.013-65 98.06 11-3316-37 99- 18 24.4221-37 102.93 41.6629.65 109.04 55-2030.80 109-70 58-3124.33 105.6439-09 115.9343.69 120.12Vt= 1.233821 + 0.0014089 t + 0*052240 t2.vt = 1~278204+0~0015261 ( t - 30)+ 0.053740 ( t -2'.1.23382 11.2500721.2695531.296391.318991-3243LIQUIDS BETWEEN ONE AND TWO ATMOSPHEUES' PRESSURE. 2,543to.0.010.5619.1728-2331.98Ethyl Bromide.a x 1Oa. to. 0.72-99 0.0 0.66746379.45 5.17 0.67204685-74 &75 0.67529390.80 17-58 0.68356296.53 25.42 0-69109831-54 0.697345=0.667463+0*0,87466 1+0.0,2307 1'.Aniline.to. a x lo6. to.0.0 32.94 0.010.66 34.54 5-2520.42 36.35 21.8930-38 38-25 30.6339.57 40.25 50.1249.69 42-76 41-6560.04 45.08 62-3573.56 48-88 79.0485.70 52.43 98.9585.50 52-10~t=0*962534+0.0:379697 t+O*0~8005 t2.?'t = 1.004384 + 0.03869 53 (l - 50) + 0.051 288 (1 -Ethylene Chloride.21.0- 9625340.9667590.9803731 * 0044 890.997 1171.0153191.030741.050030-98771350)'.[50-lOO"].to. a x lo6. to.0.0 48.17 0.010.81 51.95 5.5519.31 55-31 15.4120-5 1 55-53 2 1-0330-52 60.08 31-9825.45 57-72 40- 1327.25 58.56 50.7439.15 64-16 59.7750.23 69-93 74.9859.79 75-6773.50 85-02t?t=0.779738 + 0.0386779 t + 0*051459 t2.~t = 0.8 1 6 7 8 5 + 0.039 84 2 ( 1 - 4 0) + 0*051 9 43( t -2'.0.7797380.78457 10.7934570.7986380.8089620.8169120-8275790.8370430.85359 140)?. [40-80"].Acetic Acid.to. a x 10". to. 2).18.98 75.10 19.36 0.95 180129-55 81-36 24-97 0-95768539-51 87-19 29.54 0.96238839.37 86.73 34-26 0.9 6 7 3 749-23 93-57 39.57 0.97301660.80 102.03 49-69 0.9839377-44 114.00 60.04 0.9955173-48 1.0107879.11 1.0175599-07 1.04250[ 6O-1OO0].7't= 0.95246 1 + 0.0010266 (t-2O)+0.O51212 (t-20)'.~t ~0.99546 + 0.001 110 (t -- 60) + 0*0,2405 (t - 60)2.8 c 2544 TYRER : ADIABATIC AND ISOTHERMAL COMPRESSIBILITJES OFto.14.6721-1030.7740.0050.1360.1573.0782.00Nitro b e nz e n e .a x lo6.to.37-33 12- 9538.91 2 1-2541-10 30-7343-26 39-1045.43 49.9948-41 68.5352.2654- 92~t=0*826343+0*0367665 (t- 13) + 0.06162 (t- 13)'.Ethyl Zodide.to. a x loo. to.0.0 59.7 1 0.012-17 65.0 I 10-3323.86 70.86 19.1540.85 80.28 39-3252-10 88.08 24-2062.60 95.83 46-4553.8062.72vV~ = 0.604927 + 0.0366522t + 0*051072t2.W t = 0622849 + 0.036295(1- 30) + 0*061114( tm-Xylene.to. a x 10';.to.0.0 57-27 0.015.10 63.44 18-832 1.38 66.49 22-6230.92 71-16 ( 9 ) 29.6232.73 71-67 39-3740.69 75.82 60.5449-72 80.76 69-2861.60 88.00 75-9278-83 97.21 78.8698-86vt = 1.1344 17 + 0*001092 6t + 0-05146 lt' ,~ ' t = 1~192698+0~0012402(~- 50)+0.0,2002(t-Ethyl A ce t at e .to. a x lo6. to.0.0 70.30 0.019-28 83-02 18-2221.89 84.81 27-1830.62 91.50 34.0534- 13 94.93 41.0440.47 100.34 52-2350.14 109-39 59-9362.35 122.9 73.2162.90 123.6~ t = 1~081456+0~0013700t+0.053282t2.Vt= 1.14154 +0*0216247(t- 40) + 0.054028( 1-V.0.8263090.8319840.8385380.8444020.8522090.858420[ 13-60°].V.0.5049270.5 108 8 10.5161440.5288080.5 19 1720.533 5 1 20.5384640.6446230)2.[30-601.2' *1.13441 71.1555001-1598771.168081.1796941.1933671.204381.226271.2 301 21.25867-50)'. [50-100°].21.1.0814561.107511.1211171.1319091.1432101.1619701- 17 5521.1999440)'. [40- 8 0 O . LIQUIDS BETWEEK ONE AND TWO ATMOSPHERES’ PRESSURE. 2545to.2.406.4514.1219.3724.4235-7546-9563.5175.3386.7590.22a x lo6.Old resultscorrected.50.1049-0547-1846.0045.2 144.0843-1942.8042.6742.8 142.88Water.to.9.7111.5110-9814.2319.3820.3824.9824-2929-4634.6238.9047-9560.6573.5084.40a x 10’.New results.48.3548-0348.1347.3 146-2 146.0945-3445-3744.5643.7643.6943-0442.55 ’42.5743-00Isothermal Compressibilities and Values of dv/dt.Values of d v l d t were determined by differentiating the equationsgiven in the foregoing tables. For the wider temperature rangeswhere two equations were necessary, i t was found that there wasusually a slight break in the continuity of the d v l d t values atthe intermediate point.This break was removed by plotting theresults, and then drawing a smoothed curve, from which values ofd v / d t were read. I n addition, the accuracy of the results waschecked by calculating them in another way. The mean value ofd u / d t between each pair of succeeding points was determined bysubtracting the specific volumes and dividing by the temperaturedifference.The result was taken to refer t o the mean ternpe_rature.Then, by plotting a curve of all the values thus obtained, resultswere obtaineld a t regular temperature intervals, which, in general,agreed excellently with the values obtained from the equations.From the values of d v / d t and the adiabatic compressibilities,values of the isothermal compressibility P have been calculated byaid of the thermodynamic equation given in the introduction. Aknowledge of the specific heat a t constant pressure (C,) is alsonecessary. As already explained, comparatively large errors in thelatter quantity affect the calcula€ed values of fi but slightly, andso no special determinations of specific heats have been made, butresults obtained by other investigators have been relied on.Forbenzene and carbon tetrachloride, the specific heat determinationsof Mills and McRae ( J . Physical Chem., 1910, 14, 797; 1911,15, 54) have been used in the calculations. Schiff’s results(Annalen, 1886, 234, 300 ; Zeitsch. physikal. Chem., 1887, 1, 376)were employed in the cases of toluene, nz-xylene, ethyl acetate2546 TITREII : SDIABATIC AND ISUTHERMAL COMPRESSIJITLITIES OFand clilorobenzene ; Regnault's results (" Relations des ExpQri-ences" and Mem. de Z'Accrd., 1862, 26, 262) for carbon disulphide,ether, ethylene chloride, ethyl iodide, chloroform, and ethylalcohol. I n the case of aniline, Griffith's results (Phil. Mag., 1595,[v], 39, 47, 143) were used. I n a few other cases, the values ofthe specific heats employed in the calculations are the mean valuesof several observers.These are given in the tables.B enz ene.to.01020304050607080to.010203040506070to.01020304050to.010203035a x 105.56.0061-0066.3272-0078.2685-1292.99101.9111 1.5t l l p t .0.00 13 1613511387142414641509156116231694Car6 o n Tetrachloride.a x 10'.63.2668.1473.2878.8585-3292.90101.20109.60&./(it.0*00072007417764278848147843287439071Garb o 7% Disulphide.63.21 0*000881866.79 912060-50 9422(34.52 972469.08 1002674.6 1033a x 106. dvJdt.Ether.a x 10'- dl+lt.114.30 0.00205 1127-05 2159140.85 2268158.7 2376169.0 2430u x lo';.8 1.9588.4595.65103.1511 1-41120-51130.03143.16156.5p x 106.91-0398-31105.96114.34123.94134.97147.16:159.81B x 106.81.4487-5293.84100.55107.92116-3k? x 106.152.97170.31188.9721 1.8244.1,IQUIDS BETWEEN ONE AND TWO ATMOSPHERES' PRESSURE.2547Ethylene Chloride.to*01020304050607080to.0102030405060708090to.02020304050607080to.010203040506070to.010203040506070a x 106.48-2361.6055.4259.8064.5969.7875.8082.5389.95a x lo6.32.8934.4 736.2538.2040.3242-6345-1847.8350.5753.45tlvldt.0.00086788970926095 6098750.00 102 2106011001143Aniline.LI'L'ICEI.0-00079808120827084288595877589679180942096 90Chl or0 b enze ne.R x lo6.clr;/clt.49.40 0.000841052.66 860056-03 878359.69 898563.73 920068-10 943872.88 968378.00 993883.50 0~001019a x 106.58.7563.0367.5072.4578-1084.1290-8098-16Toluene.dvldt .0-0011631200123912811328137914331490Ethyl Iodide.a x 106.59-7264.1068.7373.8779.7386.4593.80101-75dddf.0.00056525868608 1629665166735695871868 x 10"70.0575.1580.7386.9793.75101.20109.73119.17129.60B x 106.41-3143.5745-8648-3451-0453.9557.1560.5164-0767.87B X 106.67.0271.1275-2379.8285.0290.4296.28102.64109.29B x 106.79.3484-9490.8097-28104.70112.76121.57131.23B x 106.85-5992-4099.53107.29115.86125.40135.72146.82548 T Y R ~ K .: ADIABATIC AND ISOTHERMAL COMPRESSIUILITIES OFE thy1 Ace tute.to.010203040506070to.01020304050601".01020304050607080to.01020304050607075to.0102030405060708090100a x 10'.70.3076.4383-4191.2299.86109.25120.1133.4dvldt.0.0013701434150015671635170817841864C hl oro f or Tn .a x lo6.68-6462.9868.3174-1080.4887-3394.70a x 10'.57-2761-4065.6970.3575-4880.9387.0493-40100~00dvldt.0-0007940823086388863921895980-0010005m- X y 1 m e .d L'jlLt.0.00109251121114911791210124312791316135GE thy1 Alcohol.a x 106.83-8589-5295-65102.20109.62117.82126.65137-04142-95a x lo6.50.7546-1544.5243.6043-0242-7042.6042-7643.0543.3548.38dYltU.0.00 12881326136514131470164216241719I825ll'ntc~.dv/dt.+ 0*0,88 + 0-032073043804555265926557207 82- 0.046813 x 10,;.96.29104.98114-72125.3137-0149.8164-2181.4B x 1 0 .85.9092-94101.16110.04119.96130.74142-46B x 106.75-3980.4785.6991.3897.67103.9011 1-56119.24127-30P x 106.99.95106.28113.07120.61129.12138.78149.34161.8168.9P x 109,50-7848-4346-4545-2044-6944.6244.8945.4446.3 147.4348.6LIQUIDS BETWEEN ONE AND TWO ATMOSPHERES' PRESSURE.2549Ethyl Bromide.to. a x 10'. dvldt. Cp.* /3+ 10;.0 72.99 0,0008747 0.210 109.0510 79.05 9208 0.213 119.3420 86-45 9669 0.216 131.1830 94.84 0.00 10129 0.219 144.2040 103.70 1059 0.223 157.3* Cnlculated front rosults of Regnanlt (Zoc. tit.) and Battelli ( A t t i R. Accnd.Lincci, 1907, [v], 16, i. 243).Acetic Acid.to. a x lo6. dvldt. C,. * B x 106.15 72-80 0.001 01 9 0.480 88.7120 75.73 1029 0.485 91.9830 81-55 1048 0.494 98.4840 87.50 1068 0.504 105.1050 94-10 1093 0.514 112-5560 101.18 1122 0.523 120-66108.65 1157 0.533 129.3780 70 116.30 1200 0.542 138.57* From results of Schifl', Tiniof&ev, Ludekiog aiid others. (See Laridolt-Bornstein, " Tabellen,")Methyl Alcohol.to.a x lo6. daldt. Up.* B x 106.0 88.95 0.001409 0.570 107.5910 95-30 145 1 0.588 114.9420 101.95 1495 0.606 122.730 109.18 1543 0.625 131.040 11 7.02 1599 0.643 140.360 125.48 1666 - 1* From results of Regnaclt (Eoc. &.), Kopp (Ann. Phys. Chem., 1848, [ii], 75, 981,Timofh, (Compt. rend., 1891, 112, 1261) and Walker and Henderson (Trms. Itoy.Soc. Camdcc, 1902, [ii], 8, 105).Nitrobenzene.to. a x 10'. d'L'IClt. Up.* B x 101;.0 36-40 0- 0006730 0.338 44- 7010 38-61 6852 0.345 47.3020 40.90 6975 0-362 49.9830 43-22 7097 0.358 52.7940 45-70 7219 0.365 55-5850 48-37 7342 - -60 50.28 - - -* Prom results of Regnault (Zoc. c i t . ) and Sclilamp (Ann. Phys. Chent., 1896, [iii],58, $59).Uiscussioit of Results.As has been stated, the genesal order of error in the results forthe adiabatic compressibility is about 0.1 per cent.This is, how-ever, independent' of any possible error in the accepted value(Amagat's value) for the compressibility of glass. In any case2550 TYRER : ADIABATIC AND TSOTHEICMAL COMPRESSIBILlTIES OFeven supposing that this value contains, say, a 10 per cent. error,then the consequent error in the value of the adiabatic compressi-bility is only 0.3 per cent. in an average case. It is evident, there-fore, that very little error can arise from this source. Theaccuracy of the calculated values of P depends chiefly on theaccuracy of the values of a. Errors in the determinations ofdv/dt and C, have little effect on the value of fl.For example,a 5 per cent. elrror in the value of Cp introduces only an error of1 to 1.5 per cent. in the value of P.It must be remarked that whilst the observed values of theadiabatic compressibility refer t o a mean pressure of about 1.5atmospheres, those of dv/dt and of C, refer to the normal atmo-spheric pressure. The effect of pressure on the value of a is sosmall, however, that the results may be considered as all referringt o the atmospheric pressure, without any appreciable error beingmade. I n none of the experiments was observed a change of awith a change of pressure of about half an atmosphere. It maybe claime?, then, that the values of the compressibility obtainedby this method for low pressures are far more accurate than resultsobtained by the direct method, which yields very discordant resultson account of the evolution of a very small but important quantityof heat during compression.The effect of this evolution of heaton the results obtained by the direct method will be easily appreciated from what is explained in the note a t the end of this paper.In every case except water the value1 of both the adiabaticand isothermal compressibility increases with rise of temperature,the increase being the greater for the isothermal compressibility.For water, both compressibilities show minimum values.The theoretical application of the results obtained in this workare reserved for a future paper.Note O?L some Previous L)eter)ninatiom of the Compessibilitiesof Liquids at Low Pressures.On comparing the compressibility measurements a t low pressureswith some results of early investigators, it' was found that resultswhich were considered by their authors to be isothermal are reallyadiabatic.On studying the work of Quincke ( A I ? ~ .Phys. Chem., 1883, [iii],19, 401), i t was found that, judging from his method of deter-mination, his results could not possibly be isothermal, but wereundoubtedly adiabatic. The same was found to bs the case forthe determinations of Grassi (Ann. Chdm. Phys., 1851, [iii], 31,437), of Amaury and Deschamps (Compt. rend., 1869, 68, 1564)LIQUIDS BETWEEN ONE AND TWO ATMOSPHERES’ PRESSURE. 2551and of Collodon and Sturm (Ann. C&m. Phys., 182T, [ii], 36,113), and of a few other investigators. It is important to pointout the true nature of the results of these investigators, becausethey have always been recorded in tables of physical constants andproperties of liquids as isothermal compressibilities (see, forexample, Landolt-Bornstein, ‘‘ Tabellen,” 191 2).Their results differed very considerably from the isothermal com-pressibility determinations of later investigators, a matter whichappears to have caused some surprise, although the reason of thediscrepancy was apparently never discovered.When a liquid is compressed by a small pressure-say, by oneatmosphere-there occurs a small rise in temperature amountingt o a few thousandths of a degree, yet sufficient, if neglected, t ocause a difference of 10 to 40 per cent.in the observed isothermalcompressibility, and, as can be easily imagined, the elimination ofsuch a small change of temperature is exceedingly difficult.It can be easily understood, therefore, that early investigators,ignorant of this small change of temperature, and using therino-meters scarcely sensitive enough to detect it, would obtain, notthe isothermal compressibilities which they were attempting t omeasure, but really adiabatic compressibilities, or, more correctlyin the majority of cases, results which lay between the adiabaticand isothermal values.Quincke’s method of investigation was very similar in principleto that described above. He operated a t very low pressures, thehighest he used being, in fact, little more than 50 cm.of mercury.The latent heat liberated in the compression would be so smallas to be undetectable, and i t is quite impossible that any appreci-able quantity of this heat should have disappeared during anexperimentl. Moreover, he mentions that he worked as quickly aspossible, as then better results were obtained. Quincke himselfdoes not appear t o have considered the possibility of the liberationof heat during the compression. I n the table below, Quincke’sresults are compared with t’he adiabatic and isothermal valuesrecorded in this paper. It -will be Seen that there is quite a closeagreement between Quincke’s results and the adiabatic valueswhich leaves no room for doubt that Quincke’s values are reallyadiabatic.Grassi (Zoc.c i t . ) used a similar form of piezometer t o that ofQuincke, but he worked a t higher pressures, up to 8 or 9 atmo-spheres. A t the higher pressures, the heat produced in the com-pression would be so appreciable thatl much of i t would be lostduring the time of an experiment, but at the) lower pressures th2552 TYRER : COMPRESSIBILITIES OF LIQUIDS, ETC.compression would be adiabatic, or approximately so. Now, as theisothermal compressibility is much greater than the adiabatic,Grassi found, as a consequence, that the compressibility of a liquidincreases with the pressure, whereas it really decreases. Forinstance, it will be seen in the table that for ether, alcohol, andchloroform the compressibility, according to Grassi, is greater a tthe higher pressures.It will be noticed that where a comparison with the presentauthor's results a t one to two atmospheres is possible, Grassi'sresults agree quite well with the adiabatic values.Jt may be con-cluded, therefore, that for the lower pressures Grassi's results areapproximately adiabatic, but a t the higher pressures they liebetween the adiabatic and ths isothermal values.Amaury and Deschamps (loc. cit.) made compressibility measurements between 1 and 10 atmospheres' pressure. For a change ofpressure of 10 atlmospheres there would be quite an appreciablechange of temperature, but as they took minute readings of thevolume change and eliminated what they considered to be acci-dental changes of temperature by plotting the readings against thetime, and extrapolating to the zero point on the time ordinate,their results would be approximately adiabatic. The pressures fortheir experiments being higher than correspond with the author'sresults, i t is to be expected that their values will be somewhatlower than the new adiabatic values.From a study of the early experiments of Collodon and Sturm(Ann. Chim. Phys., 1827, [ii], 36, 113, 225; Ann. Yhys. Chem.,1828, 12, 39), it would appear that their results were largelyaffected by the negligence of the latent heat of compression, andthat, their values are, as it were, partly adiabatic and partly iso-thermal.Water 0.0" 1-1-5 50.30 60.75 50.780.0 1-105 53.93 53.21 81.44disulphide \ 17.0 1-1.5 63.78 59.35 92-301 6.0 1-1-6 59.70 59.00 85.951-1-5 82.82 83.85 99-950.0 1-1.5 116.57 114.30 152.97Benzene \ 16.78 1-1-7 66.10 64.60 93.11!::1 1-1.7 97.45 94-08 111.2( 14-32 1-1-5 134.23 132.6 178.1 EtherQuincke(loc. ci't.NEWBERY: ELECTROMOTIVE FORCES IN ALCOHOL. PART V. 25530.0"Water I Grassi(loe. G i t . )( Ethyl alcohol { 1::;Ether oh amp8,(loc. cit.) Carbon disulphide 14-0 =-- iPressurefound tohaveno influenceon the com-pressibility.1-7-821-3-411-1-581-8-361-2-301-9-401-1-671-8-971-1-261-1-301-1.9250.349.948-0131.0111.0140.0163.082.885.390.499.162.864.876.31-10 83-51-10 91.11-10 109.01-10 128.01-10 63.550.7549.7748.20-114.30132.3087-9591.3562.2304-00----83-8592.50114.30132.3058-2850.7 849-7748.25-152.97177.6104.6108.391.795.0----99.95109-5152.97177.690- 1The rwults of other investigators were carried out a t sufficientlyhigh pressures to ensure the complete elimination of the heat ofcompression.The practical part of the work was carried out in the PhysicalChemistry laboratories of the University of Geneva.THE UNIVERSITY,MANCRESTER

ISSN:0368-1645    

DOI:10.1039/CT9140502534

出版商:RSC    

年代:1914

数据来源: RSC

摘要:

NEWBERY: ELECTROMOTIVE FORCES IN ALCOHOL. PART V. 2553CCXXXVI1.- Electromotive Forces in Alcohol. Part V.The Dropping Electrode in Alcoholic Solutions.By EDGAR NEWBERY.MEASUREMENTS of the electromotive forces of concentration cellspromise to furnish the most satisfactory method of comparing thethermodynamic potentials of an electrolyte in two dilute solutionsin the same solvent, and in earlier papers of %his series such applica-tions with calomel and hydrogen electrodes in alcoholic solutionshave been dealt with.A comparison of the thermodynamic potential of an electrolyt2554 NEWBERY : ELECTROMOTIVE FORCES IN ALCOHOL. PART V.in one solvent with that of the same electrolyte in another solventcannot. a t present be made, previous attempts notwithstanding, byany known electrometric method.The use of concentration cellscontaining two diflerent. soivents must at present be whollyexcluded, as the potential difference a t the boundary cannot bedetermined directly, and cannot even be roughly estimated, as thecalculations involved must be based on theoretical assumptionswhich would have a purely speculative character.For this reason the work described in the present series of papers(Hardman, Lapworth, and Partington, T., 1911, 99, 1417, 2242;1912, 101, 2249 ; this vol., p. 2302) is being developed along severaldifferent lines, which it is believed may ultimately converge a t amore promising point of attack. It, is sufficient a t present toindicate that this point is considered to be the determination of thedifference in absolute potential of two electrodes, one in any suitrable aqueous solution, and the other in any suitable alcoholicsolution, and for this purpose it is clear t'hat the precise valuesof the absolute potentials are not required t o be known; moreover,the matter is greatly simplified if conditions can be devised sothat the absolute potentials of the two electrodes in question areidentical.Direct determination of the absolute potentials of electrodes insolutions in both solvents offers one possible line of investigation,and of methods hitherto suggested f o r such determinations thedropping electrode and the capillary electrometer are the onlydevices which it is necessary to consider.It is well known thatthere are great difficulties in reconciling the results obtained bythe use of these two instruments even in aqueous solutions, and$there are already reasons f o r supposing that the most rapid progressis likely t o be inadel by further study of the capillary electrometer.'The present communication furnishes additional evidence of theuntrustworthy character from the present point of view of measure-ments made with the dropping electrode, even when the resultsexhibit most perfect consistency, and in later communications i twill be shown that the capillary electrometer promises to providethe material necessary for bridging this gap in the applications ofelectrometric methods.The dropping electrode has been applied t o the determination ofabsolute potentials in aqueous solutions by Paschen (Ann.Phys.Chern., 1890, [iii], 41, 42) and by Palmaer (Zeitsch. physikal.Chern., 1899, 28, 259; Zeitsch. Elektrochem., 1903, 9, 754), andothers.The apparatus used in the experiments described in the presentcommunication was similar t o that used by Palmaer (ZeitschNEWBERY : ELECTROMOTIVE FORCES IN BLCOHOL. PART V. 2555E'lektrochem., 1903, 9, 755), but with the following modifica-tions :(1) Pressure on the mercury was obtained by connecting a largepear-shaped vessel with the mercury dropper by means of 450 cm.of canvas-lined pressure tubing, and raising this vessel when fullof mercury by means of a cord passing over a pulley.(2) The electrode vessel was arranged so that it could beimmersed in a thermostat a t 25O.(3) A small burette, B, holding about 2 c.c., was fitted t o theAtop of the electrode vessel, to allow for the addition of smallmeasured quantities of any required solut,ion without, disturbingthe apparatus.A slow current of pure hydrogen, obtained by the electrolysisof pure sodium hydroxide solution, was passed through the appara-tus for some hours before t'aking measurements, and continuedthroughout all the experiments, except in those where hydrogensulphide was used2556 NEWBERY : ELECTROMOTIVE FORCES IN ALCOHOL.PART V.Potential differences were measured by means of a carefullycalibrated metre potentiometer wire, a Weston cadmium cell beingused as standard, and a sensitive capillary electrometer as nullinstrument.Connexion of the potentiometer with the dropping mercury wasmade by means of a platinum wire dipping in the mercury in thepear-shaped vessel, and with the still mercury by a platinum wiredipping in the end of the syphon tube D.A is the leading tube of the experimental calomel electrode, andthe U-tube ‘below contained the same liquid as the calomel electrodevessel.With a pressure of 5 atmospheres, 250 C.C.of mercury fell intwentx-f our hours in N / 10-potassium chloride.(a) As a preliminary experiment, the absolute E.M.F. of thecalomel electrode in N/lO-potassium chloride solution a t 2 5 O wasdetermined. I n this experiment the following observations are ofinterest:(i) Rapid fluctuations of the potential of the still mercury wereobserved when the potential difference between the dropping andstill mercury exceeded 3 or 4 millivolts.These fluctuations wereobserved by Palmaer only when using hydrogen sulphide in forminghis null solution, and were attributed by him t o the presence ofsolid mercury sulphide. Similar fluctuations are, however, observedin many other cases, notably when the single potential of a metalcathode is measured during electrolysis of a dilute acid. The fluc-tuations are therefore in all probability due to the lack of balancebetween the solution pressure of the metal and the osmotic pressureof its ions present in the solution. They may be completely stoppedby the additjon of a soluble salt of the metal in question.(ii) The null solutions used by Palmaer a t 1 8 O were found to beunsuitable f o r use a t 25O, a greater proportion of potassium cyanidebeing required to render the solution null.I n the first experiment 40 C.C.of a solution containingO*lN-potassiurn chloride, O*OlN-potassium cyanide, 0.0008N-potass-ium hydroxide, and 0*0004N-mercury cyanide were placed in theelectrode vessel, and a similar solution without any mercury saltand with ten times the concentration of potassium cyanide wasplaced in the small burette.Henderson’s equation was employed in this and other cases t odetermine the diffusion potential due to dissimilarity of the liquidin the dropping electrode and calomel electrode vessels respectively.I n all caws it was found to be of the order 0.1 millivolt, and wastherefore neglected.The following table gives t,he last six readings, where column NEWBERY: ELECTROMOTIVE FORCES IN ALCOHOL. PART v.2557sliows the burette reading in c.c., I1 the E.U.P. of the calomelelectrode a,aainst the dropping mercury, and I11 the difference ofpotential between the dropping and still mercury :I. 11. 111.0.25 ,) 0.579 )) 0.6 7 ,0.29 ,) 0.582 ), 0.0 Y 70.14 C.C. 0-571 volt. 3.2 millivolts0.21 ,) 0.575 ,, 0.8 millivolt0.32 ,, 0.584 ,, -0.6 ,)0.48 ,, 0-611 ,, - 1.6 millivoltsHence the absolute potential of calomel electrode in N / 10-potass-ium chloride solution at 25" is 0.582 volt.This experiment was carried out three times, giving the values0.582, 0.582, and 0.583 volt respectively, the mean result being0.582 volt.Assuming the temperature-coefficient of the decinormal calomelelectrode to be 0.0008 volt per lo, this would lead to the value0-576 volt a t 1 8 O , as compared with Palmaer's value of 0.574 volt.( b ) Attempts t o determine the absolute potential of the calomelelectrode i n saturated alcoholic salt solution were made, the sameapparatus being used, but with the following modifications :(1) The calomel electrode vessel was specially made wit'h wideleading tubs and wide-bore tap (4 mm..).(2) Connexion between the two electrode vessels was made bybringing the liquids into actlual contact instead of using moistfilter paper, as was done with aqueous solutions.This was done byopening the pinch-tap a t C and sucking the air out of the joint.(3) A delicate Ayrton-Mather reflecting galvanometer was usedas null instrument inste'ad of the capillary electrometer.The sclution in the electrode vessel was 40 C.C.of a saturatedsolution of pure sodium chloride in pure alcohol (dried overcalcium), t o which was added mercury cyanide until 0'000125normal.The burebte contained a 0401N-solution of sodium cyanide inalcohol previously saturated with pure sodium chloride.The following table gives the last five readings, the figures I, 11,I11 having the same significance as before:I. 11. 111.0-14 C.C. 0.330 volt. 34.0 millivolts.0-32 ,, 0.330 ,, 21-4 ,;0.54 y y 0.331 )) 10-6 ,)0.68 ,, 0.331 )) 1.0 Y Y0.77 ,, 0-331 )) -33.4 ))Absolute potential of the calomel electrode in saturated alcoholicA second experiment by the same method gave the same resalt.VOL. cv.8 Dsodium chloride solution = 0.331 volt2558 NEWBERY : ELECTROMOTIVE FORCES IN ALCOHOL. PART v.A third experiment, using O*O'IN-sodium sulphide solution inplace of the sodium cyanide, gave 0.329 volt.A fourth experiment made six months later with a fresh set ofsolutions similar to those used in the third experiment gave again0.329 volt. Average of the four results=0'330 volt.( c ) An attempt was next made to determine the absolute poten-tial of the calomel electrode in saturated aqueous sodium chloridesolution.(i) A saturated solution of pure sodium chloride' containing0.000125N-mercury cyanide was placed in the electrode vessel, anda similar solution containing 0.13-sodium cyanide in place of themercury salt was put into the burette.On adding the solution from the' burette until the concentrationof the sodium cyanide was two hundred times that of the mercurycyanide, the potential difference between the falling and the stillmercury was reduced from 500 to 50 millivolts.Further additionof sodium cyanide produced a still smaller effect, so that it appearsto be impossible to produce a null solution by this method, whichwas theref ore abandoned.(ii) Palmaer's method of obtaining a null solution by passinggaseous hydrogen sulphide through the liquid was then tried, but,instead of adding acetic acid t o reduce the ionisation of the hydro-gen sulphide, it was found necessary to add sodium hydroxide t oincrease ii;.After making the saturated sodium chloride solutionnearly centinormal with respect t o sodium hydroxide and passinghydrogen sulphide for eight hours, the pot8ential difference betweenthe dropping and still mercury had only been reduced t o 10 milli-volts. The fig-ures obtained showed that if a null solution couldbe obtained by this method it would probably give a value ofmore thctu 0.6 volt for the absolute potential of the calomel elec-trode in saturated aqueous sodium chloride solution. Subsequentexperiment showed that this result is undoubtedly too high.(iii) Sodium sulphide was then tried as the agent for reducingthe Concentration of the mercury ions, a 0.001N-solution in satur-ated sodiurr, chloride solution being placed in the burette, whilst40 C.C.of a saturated sodium chloride solution containing0*000125N-mercury cyanide were placed in the electrode vessel.A slow current of pure hydrogen was passed through as in Z(a).The following table shows the results obtained, the figures I, 11,I11 having the same significance as before [Z(a)ii], whilst column IVshows the time interval between the readings:NEWBERY : EJ,ECTROMt)TIVE FORCES IN ALCOHOL. PART V. 2559I, 11. 111. IT'.0.00 C.C. 0-573 volt. 504 millivolts. 30 minutes0.72 ), 0.579 ,, 482 9 , 30 Y,1-44 ,, 0.586 ,, 277 ? ? 30 ,,2.25 ,, 0.595 ,, 206 9 , 21 hours2.25 ,, 0.591 ,, 255 ,, 30 minutes2-52 ,, 0.594 ,, 230 ,) 30 ,,2.70 ,, 0.595 ,, 174 ,, 30 ,,2-88 ,) 0.595 ,, 60 Y , 30 ),2-92 ,, 0.595 ,, -33.4 ,, 15 Y 72.92 ,) 0.593 ,, -10.6 ,, 21 hours2.92 ,, 0-593 ,, +238 9 ,1.80 ,, 0-588 ,, 250 1 , 30 ,,2-88 ,, 0.595 ,, 85 7, 15 ,,Frcin this table i t will be seen that a null solution is readilyobtained by the use of sodium sulphide, the potential of thedropping mercury remaining constant whilst the potential of the&ill mercury altered by 200 millivolts.The addition of sodiumsulphide only affected the potential of the dropping mercury to avery small extent when near the null point, although the effectwas slightly greater when far away from it.The effect on the potential of the still mercury was remarkable,although a t first it was comparatively small. When near the nullpoint, however, further addition of sodium sulphide, sufficient toincrease its concentration by 0*00005N, lowered the potential bymore than 100 millivolb, the greater part of which took placewithin the first ten minutes, reaching the maximum after aboutthree or four hours, and then falling again.Another remarkable feature of this experiment is the accuracyand certainty with which these results may be reproduced.Theexperiment was repeated three times, using fresh solutions eachtime, but exactly the same result (0.595 volt) was obtained. Byovershooting the mark with excess of sodium sulphide, and subse-quently returning to the null point by addition of mercurycyanide, the same result was again obtained. Also, after the seriesof experiments had been completed, the apparatus was dismantledand laid aside for six months.It was then refitted, new solutionswith materials from other sources used, and the above experimentrepeated, when exactly the same result was again obtained. Again,from the last line of the above table, i t will be seen that by allow-ing the liquid to remain (with the hydrogen passing a t the rate ofthree bubbles per minute) for twenty-one hours, the potential ofthe still mercury had risen again nearly 250 millivolts. On addingmore sodium sulphide the null point was again reached, and thefigure in the second column again became 0.595 volt. The actualquantity of sodium sulphide present thus appears to have little orno effect on the pocential so long as the null point is attained, andits addition can therefore cause no perceptible diffusion potential.8112560 NEWBERY : ELECTROMOTIVE FORCES IN ALCOHOT,.PART V.(iv) A similar experiment was carried outl with a normal solutionof sodium chloride in place' of the saturated solution. I n this casea greater concentratioii of sodium sulphide was required t o producethe null solution. The fluctuations of potential of the still mercurywere also greater and more persistent than in the previous case.Two determinations gave identical results, namely, 0.552 volt, asthe absolute potential of the calomel electrode in a normal solutionof sodium chloride in water.(v) When a similar experiment was tried with O*lX-sodiumchloride solution, the fluctuations of potential referred to previ-ously were very violent, a t times showing a variation of 40 milli-volts, and were never entirely absent.Also a high potentialE.U.F. appe'ared to be generated by the dropping mescupy, sincetouching any metallic connexion on the apparatus with the fingeror an earthzd wire a t once gave a large deflexion to the galvano-meter, which continued until the earthing body was removed. Asthe direction of this deflexion was determined by the side of thegalvanometer which was touched, i t was considered advisable toinsulate Lhe whole apparatus on blocks of paraffin-wax before takingfurther readings.Three determinations of the absolute potential of the calomelelectrode in O*lN-aqueous sodium chloride solution gave the values0.534, 0.535, and 0.535 volt respectively.(vi) It was found possible to produce a null solution in thecase of decinormal sodium chloride solations by the use of sodiunicyanide and also by the use of hydrogen sulphide and acetic acid,although neither of these methods could be used with the strongersolutions of sodium chloride.The use of sodium cyanide gave thefollowing result :Absolute potential of calomel electrode in N / 10-sodium chloridesolution = 0.579 volt.The use of hydrogen sulphide and acetic acid gave:Absolute potential of calomel electxode in AT/ 10-sodium chloridesolution = 0.570 volt.Summary.The following figures are given by the dropping electrode as theabsolute potentials of t'he calomel electrode in the solutions stated,a t 25O:(a) ( / I )In saturated sodium chloride (aqueous) ...0.595 volt.,, normal ,, ,, (aqueous) ... 0.552 ,, 7 Y 9 , 7 ) ,, (alcoholic) ... 0.329 ), 0.331 volt.y y decinormal ,, , Y 9 , ... 0.535 y y 0.579 y ,Y Y ,, potassium chloride ,, ... 0.572 ,) 0.582 ,NEWBERY: ELECTROMOTIVE FORCES IN ALCOHOL. PART V. 2561The figures in column (a) were obtained with the aid of analkaline sulphate, hhose in ( b ) with an alkaline cyanide.Of these figures, the value given in ( b ) for N/10-potassiumchloride solution at 2 5 O may be taken as approximately correct, asit is nearly the same as that) obtained by Palmaer (Zoc. cit.) whencorrected f o r temperature from the known coefficient of the calomelelectrode, and is also supported by Smith's observations with thecapillary electrometer (Zoc. cit.).The value given in ( b ) for N/lO-sodium chloride solution mayalso be taken as approximately correct, since it is within threemillivolts of that for potassium chloride.A concentration cell withcalomel ,electrodes and N / 10-solutions of sodium chloride andpot,assium chloride in opposition showed an E.M.F. of about2 millivolts.Even a superficial examination of the remaining figures will atonce show that they cannot represent true absolute potentials.The potential of the calomel electrode according t o these results isgreatest in the saturated solution, and least in the most dilute.This is directly contrary to theory, and will be shown later (PartVII) to be contrary to fact.Apparently the use of the alkali sulphide is responsible in parta t least f o r the abnormal results.It was made use of (1) becausei t was the' only substance found t h a t would give a null solutionat all with the stronger aqueous solutions, and (2) because inalcoholic solution i t gave almost the same result as sodium cyanide,which presumably gives true values at least' in aqueous solution.Again, the reason why the sodium sulphide produces a nullsolution with saturated aqueous sodium chloride, when hydrogensulphide will not, is by no means evident. If i t is suggested thatit is duel t o the greater extent, of ionisation of the sodium sulphide,then i t should follow that. more sodium sulphide should be requiredin the saturated sodium chloride solution than in the normal ordecinormal, f o r the sodium sulphide must obviously be less disso-ciated in t'he more concentrated sodium chloride solution. Thisconclusion is not supported by experimental facts, for it was foundthat the saturated sodium chloride solution required less than halfthe quantity of sodium sulphide that the normal solution required,and the normal solution required a little less than the decinormal.The foregoing data have been given at some length as theypossess so much of definiteness, and therefore must have somespecial significance which must be considered in any satisfactoryexplanation of the theory of the dropping electrode, for it will beshown in a future communication that these results, although s2562 JONES AND WHEELER :cleSiiite, afford no clue to the absolute potential of the calomelelzctrode in alcoholic or in concentrated aqueous solution.The author desires t o express his thanks to Professor Lapwortlifor his mcouragement during the progress of the work, and begst o acknowledge that some of the apparatus used had been pur-chased from a grant to Dr. Lapworth from tlie Government GrantResearch Fund of the Royal Society.CHEMICAL LABOltArOlLIES,MANCHESIER UNIVERSITY

ISSN:0368-1645    

DOI:10.1039/CT9140502553

出版商:RSC    

年代:1914

数据来源: RSC

摘要:

2562 JONES AND WHEELER :CCXXXVIII.-The Compositioyh of Coal. Part 11.By DAVID TREVOR JONES and RICHARD VERNON WHEELER.IN a previous communication (this vol., p. 140) the result of distil-ling bituminous coal in a vacuum a t a temperature of 430° wasrecorded. It was noted that there did not appear t o be muchdifference in character between the liquid distillates obtained a tthat temperature and a t 350O. It seemed desirable t o examinefurther the character of the oils obtained a t a temperature notexceeding 350O.It will be remembered that on distillation a t 430° in a vacuum,bituminous coals yielded, besides gaseous products and water, about6.5 per cent. of their weight of tar. On distilling this tar, abouthalf remained a s pitch, boiling above 300O. The oils boiling below300° consisted mainly of unsaturated (ethylenic) hydrocarbons,40 t o 45 per cent.; naphthenes (C,H,,) and liquid paraffins, form-ing together about 40 per cent.; phenols, 12 to 15 per cent; andaromatic compounds, about 7 per cent.An examination of the corresponding oils obtained from thedistillates from coal in a vacuum atl 350°, details of which aregiven in the experimental part of this paper, showed them to con-tain the same compounds in similar proportions.The occurrence of aromatic compounds in the oils obtained a t thislower temperature requires explanation.I n accordance with a general theory respecting the compositionof "coal," put forward to explain the rapid formation of thevarious types of compounds found in coal distillates, the presencein coal was assumed of hydrogenated aromatic nuclei (or " bound ''molecules), which, i t was suggested, suffered decomposition, elimin-ating hydrogen, a t temperatures not much below 400°-the hmTHE COMPOSITION OF COAL.PART 11. 2563perature at which dihydronaphthalene has been found to decom-pose, thus:I n the light of the results recorded in the present paper, somemodification of this theory is required, so far as it affects thearomatic compounds.The mechanism of decomposition of santonous acid, Cl6HlOOs, asoherved by Cannizzaro (Gaaaetta, 1884, 13, 385), suggests an alter-native. This acid decomposes between 300° and 350°, yieldingchiefly 1 : 4-dimethyl-5 : 8-dihydro-&naphthol and propionic acid, inthe following manner :CMe CH, CMe Ci12/\/\ /\/\\/\/ \/\/Hoe$! # FH*CHMe*CO,H ~ Ho'g $ 1;' + CH,Me*C02HCH c CK, H C CHCMe CH, CMe CH,I n an analogous way, the formation of naphthalene derivativesfrom hydrogehated nuclei in coal can be explained:CH CH+ RH./\/\\/\/QH Q QHRCH C CH,CH CHAccording to this decomposition, elimination of hydrogen doesnot necessarily occur.Additional evidence of the occurrence of free pa.raffins in coal, t owhich reference was made in our previous paper, has been obtainedby Knecht and Hibbert (Mem.Manchestea Phil. SOC., 1913, 58,No. 2), who, in the course of a research on the soluble portions ofsoot., obtained a paraffin, C2,HS6, which they identified with hepta-cosane. This paraffin appears to be the same as that described byus as having a molecular weight intermediate between the valuesrequired for CfGHj4 and C271156 (Zoc.cit., pp. 141 and 143)2564 THE COMPOSITION OF COAL. I'ART 11.EXPERIMENTAL.One and a-half kilos. of a Durham bituminous coal, in piecesabout 0.3 cm. cube, dried a t 105O, were distilled in a vacuum a t350° in the manner dmcribed by Burgess and Wheeler (this vol.,p. 131). The temperature was maintained without interruptionduring ten days, a t the end of which time gas had practically ceasedt o be evolved. The coal was allowe'd to cool, removed f p m theretort,, well stirred, and replaced. Heating as before was thencontinued during seven days.The total amounts of tar, oil, and water collected were:Tar (No.1 receiver) ..................... 13.6 gramsOil (No. 2 receiver) ..................... 6-2 .. Water (No. 2 receiver) .................. 8.3 ..The yield of tar and oils a t 350° was thus 1.25 per cent. of theweight of coal used.The tar in No. 1 receiver had D:iO*9639. The aqueous solutionobtained on washing this tar gave with ferric chloride the colourreaction characteristic of o-dihydroxybenzenes, probably due t ocatechol, a substance that has been found by Bornstein to exist intfhe tars obtained on coking coal a t a low temperature.The oil in No. 2 receiver (which had been kept cool throughoutthe distillation by a solution of solid carbon dioxide in ether) hadThis oil was not further examined separately, but wasadded t o the €ar in No.1 receiver. The lower aqueous layer inNo. 2 receiver was found to contain hydrochloric acid, as was thecase in distillations of the same coal a t 430O.On washing the mixed t a r and oils with a solution of sodiumhydroxide, their volume decreased by 17 per cent. owing t o theremoval of phenols.The mixture was washed successively with (1) a dilute solutionof sodium hydroxide, (2) dilute sulphuric acid, (3) a solution ofsodium carbonate, and (4) water; and, after having been dried overanhydrous magnesium sulphate, was distilled. The compositionsand specific gravities of suc&ssive fractions of the neutral oils aretabulated below :0.8358.Fraction. 1. 2. Residue. - Boiling point ............ 170- 250" 250-300'DiE ........................0.8211 0.9066 0.998Hydrogen ............... 12.46 10-71 8.68Carbon ..................... 87.73 88.86 89.4 9Carbon+ hydrogen 100.19 99.57 98-17Fractions 1 and 2 were further examinedPHOTOKINETICS OF SODIVM HYPOCHLORITE S9LUTIONS. 2565Fraction 1 on being washed with concentrated sulphuric acidsuffered a reduction in volume of 44 per cent.., due t o t'he removalof olefines. Treatment with fuming nitric acid and weak fuiningsulphuric acid effected a further reduction in volume of about6 per cent., due, for the most part, t o the removal of aromaticcompounds. The oil remaining, after washing, drying, and distil-ling from sodium in a vacuum, had the following composition:Carbon ..................... 85.39Hydrogen .................. 14.93Carbon+hydrogen .. 100.32Naphthenes, (CnHZn), require C = 85.7 ; H = 14.3 per cent.Fraction 2, treated in the same manner as fraction 1, suffered areduction in volume of 56 per cent., due to the removal of olefines,and of 6 per cent., due t o the removal of aromatic compounds. Theresidual oil contained :Carbon ..................... 85- 44Hydrogen .................. 14.5 6Carbon + hydrogen 99.99The presence of aromatic compounds (naphthalenes) was estab-lished by aspirating the vapour from the oils, when heated a t looo,through an aqueous solution of picric acid, when yellow crystals of apicrate were deposited.EYKMEALS,CUMBERLAND

ISSN:0368-1645    

DOI:10.1039/CT9140502562

出版商:RSC    

年代:1914

数据来源: RSC

摘要:

PHOTOKINETICS OF SODIVM HYPOCHLORITE S9LUTIONS. 2565CCX XXI X.- Photokinetics of Sodium HypochloriteSolutions. Part 11.By LEO SPENCER.THE present paper is an account of the1 continuation of the investi-gation begun by W. C. McC Lewis on the photokinetics of sodiumhypochlorite solutions (T., 1912, 101, 2371), in which it wasshown that the main reaction involved in represented by theexpression NaClO -+ NaCl t- 0.For greater convenience and accuracy the method of estimatingthe hypochlorite was carried out, as follows: I n order t o diminishas far as possible any changes produced by the lowering of the levelof the liquid in the reaction space, the amount of liquid titratedwas limite'd t o 10 c.c., which made it difficult t o estimate thestrength of the solution by arsenious oxide and starch-iodide paper.To 10 C.C.of the hypochlorite solution was added 0.02N-arseniou2566 SPENCER : PHOTOKINETTCS OF SODIUMacid in very slight excess, then 0.5 C.C. of a 1 per cent. starchsolution, and 1 C.C. of a 10 per cent. solution of potassium iodide,the1 solution being afterwards tJtrated with O-OliV-iodide. Theamount of Cosine solution was generally less than 1 c.c.; thus errorsdue to evaporation of iodine were avoided, and a sharp end-pointobtained. With free alkali o r acid present, excess of sodium hydro-gen carbonate was added, i t having been noticed previously thatthe end-point was but little affected by thelatter or by sodium carbonate. Duplicate/6'titrations were done a t each determination,and the values obtained did not usuallydiffer more than 0*2-0*3 per cent.fromeach other.EXPERIMENTAL.As source of light the same uviol lampwas used throughout the work, and all theapparatus, except the outside vessel, was ofuviol glass (see figure). The lamp was en-closed in a uviol sheath, which fitted fairlyclosely t o it. This was held by small piecesof cork in a uviol cylinder (outside diameter,4.96 crn.), drawn out a t the bottom to anarrower tube, which served as an inlet fora continuous stream of water, which left bya sidetube a t the top, the object of thewater stream being t o keep the temperatureconstant. Around this was placed a seconduviol cylinder (outside diameter 7.03 cm.),leaving a space of 0.93 cm. between them forthe light-filter solution.On the outside of allwas the reaction vessel (internal diameter9.80 cm.), providing a thickness of 1.39 cm.of hypochlorite solution. The bottom of thisspace was 1.5 cm. above the level of the mercury in the lamp, andits height 30 cm. when full. The hypochlorite solution was stirredcontinuaIly by mechanical means. The solution was kept a t 1 5 O + l ounless otherwise stated.* The lamp was run off the 230-volt mainsin series with a self-induction and resistance; 3.6 amperes wereemployed as a rule, corresponding with a potential drop of 32.5volts across the lamp.* Thib approxiniate constancy in temperature which would be quite tooinaccurate for ordinary thermal reactions is in the present case sufficient owing tothe very small tempel-ature-coefficient (see later)HYPOCHLORITE SOLUTIONS.PART 11. 2567Prelimiizary Test.--The first point det,ermined was whether anyappreciable disturbaiice was prcduced by the level of the liquidfalling (due to withdrawals of solution for titration purposes)during the course of an experiment. The rate of decompositionwas measured, first with the reaction space full, and then only halffull. The result was as follows:Reaction space full.Time. Concentration. k .0 47.69 -0.8 43.63 0.04582-0 39-03 0.04353.0 35.39 0.0432AI \Reaction space half full.0 47.69 -1.0 42.94 0.04552.0 39.05 0.04343.0 35-33 . 0.0434,- h ,Time. Concentration. k.The time is measure,d in hours from the commencement of theexperiment.The concentration is that of the sodium hypochloriteexpressed in C.C. of 0*05N-arsenious acid. k is the unimolecularconstant 1 / t log,o a / a - x, where a is the initial concentration ofthe hypochlorite, and a - x is the concentration a t time t. Whenk is bracketed, thus [ k ] , it represents the unimolecular constantcalculat'ed for the interval just prezediiig the measurement, theinitial time and concentration being those of the previous reading,so [lc] for the interval between t, and t, is:a - .r21, - - t q a-x, - lo&lo---. 1I n ordinary circumstances the fall in level did not amourit t omore than a quarter of the length of the reaction space, so com-paratively little error could have been introduced from thiscause.Effect of Change of Concentration of the Hypochlorif e Solution.I n the previous paper it was found that for the first six hours orso the decomposition was fairly well represented by a unimolecularformula, it being noted, however, that there was a slight tendencyfor the constant t o rise towards the end of that period.The iiewmethod of analysis allowed the reaction to be followed over amuch greater range of concenhation, and as will be seen from thefollowing figures the valu? began t o rise very rapidly as lowconcentrationr were reached.Time in Concentrationhours in C.C. offrom 0-02N-beginning. As*O,. 12. P I0.0 30.77 - -3-0 21.93 0.0490 0.04905.6 16-94 0.0505 0.05228.5 10.57 0.0546 0.062711-5 6.04 0.0612 0.081015-5 1.91 0.0780 0.125019.5 0.30 0- 1027 0.201022.0 0.04 0.1401 0.3502568Hypochlorite alone 0-08N.\ Time.Concentration. k.0.0 44.71 -1.0 40.84 0.03932.3 35.66 0.04214.0 30.34 0.0421cSPENCER : PHOTOKIKETICS OF SOD1U"Mchloride 0.34N.A >Time. Concentration. k.0.0 44.21 -1.0 40.66 0.03612-0 37-39 0.03643.5 32.69 0.0375Abseiice of Ch Pmicnl A ~ t o c a ~ f n l y t i c Effects.Other products possibly formed in small amounts in the decom-position might have had a tendency t o accelerate the decompositionas they accumulated. I n order to put this t o the test, two solutionsof the same concentration with respect t o the hypochlorite wereprepared, (a) one by photochemical decomposition of a more con-centrate'd solution, and ( b ) one by simply diluting with distilledwater.If a catalyst were produced in the decomposition itself, theni t ought, t o have been present, in ( a ) and absent in ( b ) .Prepared by decomposition.Conientration. Wl '21.5 0.05910.6 0.0846-0 0.120Prepared by dilution.7 Wl A Concentration.22.68 0.05711.43 0.0825.47 0.130The equality in the value of the two rates indicated the absenceof autocatalysis, which could not therefore account for the rise invalue of the constant. As chemical changes in the reacting systemitself appear to be excluded as the cause of the disturbance, i t isnecessary t o ascribe i t t o alteration in the optical absorption whichdiffers for various parts of the spectrum. This will be consideredlaterHYPOCHLORITE SOLUTIONS.PART 11. 2569Effect of IIiin.2itc iski?ig t h e Ali:dt C'otrtetit.In the previous paper (Lewis, Zoc. c i t . ) it was found that theneutralisation of the small amount of alkali present in the solutionwas followed by an imrease in the velocity of decomposition.Further experiments have shown that the addition of a smallamount of hydrochloric acid increased the velocity, but that i t soonbegan appoently to fall as more was added. The strength of thesodium hypochlorite solution was usually 0.075N ; the amounts ofsodium carKonate and sodiu-m hydroxide present a t the ssme timewere 0.0089il' and 0.0053.N respectively. The following table con-tains the mean velocity constant li corresponding with a series ofdeterminations over a time of exposiire varying from two t o threehours, varying amounts of hydrochloric acid being added a t thecommencement .Number of experiment 1 2 3 4 5 6Concentration of hydro-chloric acid added,lents per litre of thehypochlorite solutionexpressed in equiva- 0 0.0091 0.0171 0.0253 0.0379 0.0495 1 E ........................... 0-0418 0.0510 0.0487 0.043'7 0-0304 0.0250It would appear from the above that the maximum rate isreached when the solution is about neutral. The fact that thegreatest normality of the acid added did not exceed 0.05N was dueto the large amount of chlorine formed, which rendered the titra-tion values unsteady. The first action of the hydrochloric acid isnaturally t o neutralise the sodium hydroxide present in the solutionas ordinarily supplied for bleaching purposes.Owing to the weakcharacter of hypochlorous acid the sodium salt will be hydrolysedand the degree of hydrolysis will be much increased by the addi-tion of the hydrochloric acid. Apparently, theref ore, t'he undisso-ciated hypochlorous acid molecule is less photosensitive than theion. Continued addition of hydrochloric acid introduces complica-tions owing to the reaction between hydrochloric and hypochlorousacids.EffPct of I t i c r m s i t q the AAll;ulL Content.As free alkali was present in the original solution i t was desirableto find its action on the decomposition. It was found, however,that sodium hydroxide, even in strength several times that of thehypochlorite, had only a small effect on the reaction.The effect,such as it is, represents a diminution in velocity as the alkdiincreases2570 SPENCER : PHOTOKINETICS OF SODIUMHypochlorite 0.076N.Time. Concentration. k .0.0 47.20 -0.5 45.09 0.03961.0 42.98 0.04061.75 39.92 0.04153.25 34-57 0.0416h ,- -.Hypochlorite O.O76N+sodium hydroxide 0-143N.Time. Concentration. IC.0.0 38.261.2 34-31 0-03941.7 32.79 0.03982.0 31.84 0.03993.5 27-58 0-0408-I n a parallel experiment the value of the constant was alteredfrom 0.0416 to 0*0400 by the addition of 0*358N-sodium hydroxide.Y'emperature-coe ficierat of the Reaction.The temperatuse-coefficient of the reaction was determined byI. 11. 111. Mean.k at 10" . .... . . 0.0369 0-0360 0.0373 0.0367k at 24' ....... 0.0388 0.0402 0.0397 0-0396observations* of the rates a t loo and 2 4 O .The mean values give a temperature-coefficient of 1.06 for anThis is in agrwment with many of the results interval of loo.obtaiuesd in other photochemical reactions.The Effects of Differelit Spectral Regions.I n the foregoing experiments the light from the lamp was useddirectly.For quantitative examination, however, it is more impor-tant to investigate the effect of separate regions. The action ofapproximately monochromatic light was studied by employingWinther's light filters (Zeitsch. Elektrochem., 1913, 19, 389), whichtransmit a known amount of light of a particular wave-length fromthe uviol lamp whilst ahorbing all other lines. Assuming Beer'slaw t o hold for the filters, the concentrations of the constituentswere so altered that the same amount of light passed through thefilter in the present apparatus as passed through the thicknessused by Winther.I n order t o effect this, the concentration of tlhefilter had to be altered in the inverse ratio of t.he two thicknesses.Since the thickness of the Alter layer in the present experimentsdid not differ by a largo amount from that of Wintlier, this applica-tion of Beer's law was considered to be justifiable. Winther'smeasurements were of considerable importance for the presentinvestigation, sinco they constitute the only quantitative work onthe spectrum of the uviol lamp available a t the present time.Winther's method is, however, not one of extreme precision.As a check, two experiments were carried out with water onlyin the filter space, one a t the beginning of the series, the other* The temperatnres of these measurements were kept constant to 0.5"HYPOCHLORITE SOLUTIONS.PART 11. 257 1a t the end. The respective values were k=0*0411 and 0.0423,mean 0.0417. The regions examined corresponded with the lines578, 436, 405, 366, and 313pp. The results are as follows:A 578. Plotnikov's filter (isolating the yellow region). Filter trans-mits 80 per cent. of the line ~ 5 7 8 (Plotnikov).Time in Concentration in C.C. ofhours. As,O, solution. k.0.0 35.06 Zero (that is, no appreci-4.2 35.17 able change in con-centration).A 436. Wint'her's filter, transmitting 38 per cent. of line A 436.Time.0.01.31.83.74.75.6Concentration.36.4036.0135.8535.2434-9634.73k.0-003613663803720.00365-r\ 405.Winther's filter, transmitting 34 per cent. of line A 405.Time.0.01-72.32.8Concentration.37.8137.2137.0226-85k.-0.004120.004000.00400r\ 366. Winther's filter, trmsmit.ting 27 per cent. of line A 366.Time.0.01.63.86.35.9Concentration.37-0936.4335-5435.0534.80k.0,004824874620-00469-r\ 313. Winther's filter, transmitting 30 per cent,. of line A 313.Time.0.01.32.34.34.8Concentration.36.4636.2336.0535.0635.60k.0.002082132240-002 17-I n general, thel substitution or" approximately monochromaticlight in place of the entire spectrum yielded much more consistentvalues f o r k.Duplicate experiments were carried out, and agreedwell with those recorded. Wean values of both sets are employedin the summarising table2572 SPENCER : PHOTOKINETICS OF SODIUMThe values of the concentratioiis in tlie above tables are themean of three t?itratioW. The results are suiiiiuarisecl in the accom-panying table :I. 11. Ill. IV. v. VI. VII.Per cent. Percent. Per cent.A436 pp 38 0,00368 8.8 23.2 1.0 1.0A 405 34 0.00405 9.7 28.5 0.29 4.3A 366 27 0,00475 11.4 41.7 0.25 7.1A 313 30 0.00212 5.1 17.0 0.045 16.3Complete spectrum 100 0.0417 100 --Total 110.4The wave-length is given in column I. Column I1 containsWinther's values for the percentage of the line which passes throughthe light filtez.I n column I11 are the values of the unimolecularconstants directly observed with the light-filter in position. Thelast value in this column is the one observed with water only inthe filter space. Column IV contains the values of the velocityconstants of column I T 1 expressed as a percentage of the velocitywhen water only is preselnt in the fihr layer. Column V containstlie calculated amount of decomposition, that is, the velocity whichwould occur if the filter transmitted 100 per cent. of the line andkept back all the others completely. The rate is expressed as apercentage of the rate observed with water alone in the light-filterspace. The relative intensities of the lines from the uviol lamp aregiven in column VI, being taken from the tables given by Winther.Column V11 contains the relative rates of decomposition that wouldbe produced if e'ach line were of the same intensity and separatedfrom the rest..These figures show that the fastest decomposition is effected bythe wave-length ~ 3 6 6 , at the intensity at which it is omitted fronithe uviol source. This statement is true not only when the resultsare calculated (column V) on the basis of 100 per cent.of the linepassing through-as actually occurs, of course, when no filter isinterposed-but also when no such calculation is made, the directeffect through the filter bekg measured (column IV). It shouldbe noted, however, that A366 is not the most intense line of theuviol spectrum (compare column VI).The data in column V I Ishow that; if one calculates the velocity constants on the basis ofone and the same intensity for all the lines of the spectrum, oneobtains the result that the shorter the wave-length t'he greater theefficiency, that is, ~ 3 1 3 is more effective than h 366. This is inagreement with the concept of the energy quantum (hv) and withth3 photochemical-equivalent law of Einstein, for the shorter thewave-length the greater the frequency, and hence the greater thesize of a single quantum, This uniformity in light, intensity isHYPOCHLOHITE SOLUTIONS. PART 11. 25’73however, not the actual state of things in the experiment itself.I n the actual case there is a well-marked maximum efficiency a tA 366, as shown by the figures in column V, due to the simultaneousoperation of two effects, namely, the large intensity of this line inthe lamp and the large absorbability of this region by the solution(the head of the absorption band of sodium hypochlorite lies in theregion 200pp).The shortest wave transmitted by the uviol sheathis h 290 pp (compare Lewis, loc. c i t . ) . As the wave-length increasesbeyond ~ 3 6 6 the efficiency diminishes, so that on reaching h578(a yellow line) and using Plotnikov’s filter no chemical effect isobserved at all.Returning t o the data of column V i t will be noticed that thesum of the effects of the various regions apparently exceeds by asmall amount the total value of the lamp as a whole. The mostreasonable explanation of this is that the filters not being perfecta certain amount of superposition and repetition of certain parts ofthe spectrum occurs.The result as it stands favours the view thatthe effects of different portions of the spectrum are simply additive,a conclusion already come to by Luther and Forbes ( J . Amer.Chem. SOC., 1909, 31, 770).Owing to the absence of data on the absorption-coefficient ofsodium hypochlorite solution for the various lines it is not possiblea t present to compare fully the effect of each line, and thus testBruner’s hypothesis (Zeitsch. E’lelctrochem., 1913, 19, 555), t o bementioned in the next paragraph.Further Discussion of Results.If a substance in solution obeys Beer’s law, and if I, denotesthe intensity of incident light of wave-length A, c the1 concentra-tion, h the thickness of the layer, and m is a constant, namely, theabsorption-coefficient depending only on the substance and wave-length, then the amount of light absorbed will be given by theexpression I(,A( 1 - e-mciL).I n the paper of Luther and Forbes,referred to, the view has been put forward that the amount ofchemical action is proportional la the amount of light absorbed bythe solution, and is therefore given by the expressionwhere kA is a constant for each wavelength of the incident light.Bruner’s hypothesis is equivalent t o attributing the same valueto k~ whatever the wavelength.Froin the above “ab,sorption” equation it follows that the effectof dilution on the rate of decompositdon will be different accordingto the amount of absorption that the line undergoes.A line thatis almost completely absorbed by a given thickness of, say, a centi-SkAEhlOA(1 - e-m 1,VOL. cv. 8 2574 SPENCER : PHOTOKlNETICS OF SODIUMnormal solution will naturally be still more completely absorbedby a decinormal solution. It follows that practically the sameamount of optical abs,orption occurs in the two cases, t h a t is, it ispractically complete. If photochemical action depends on theamount of light absorbed, we would expect the same absoluteamount of chemical decomposition in the two cases. This is borneout by the following experiments, using the line ~ 3 1 3 . The meanrate of decomposition of a solution initially 0.075iV was foundt o be 0.185 C.C. per hom (reckoned in terms of the arsenious acidsolution).A solution initially 0.013N was likewise found to have amean decomposition value of 0.20 C.C. per hour, a quantity verynearly the same as the previous, although the absolute concentra-tion in the former case was approximately six times as great asin the latter.Strictly speaking, there should be no unimolecular const’antobtainable ir, this case, since the law is not d x / d t = k ( n - z ) , butcl.n./dt = li. For purposes of comparison, however, the values overshort experiments werel used for thel calculation of a constant,although i t will be clear fioni the two sets of values that as thedecomposition progressed the unimolecular ‘‘ constant ” reallyrose . -%Expt. ((0. Initial concentration ofsodium hypochlorite = 0 0769( approx .) .Tim;inhours.0.01.32.34.34.8Concentration u&-in C.C. molecular.of As,O,. k.36.46 -36.23 0.0020836.05 21335.66 22435.60 0-00217Expt. ( I , ) . Initial concentration ofsodium hypochlorite =O.O13,V(approx.)Time Concentration. Uni-r A ,in in C.C. molecular.0.0 6-67 -1.0 6.46 0.01391.5 6.37 1333.5 5.97 0.0138hours. of As,O,. E .(The li of Expt. ( b ) indicates the value tlo which the b ofExpt. ( a ) has risen when the decomposition has proceeded t o aConsiderable extent.)On the other hand, if the amount of the line absorbed is small,then doubling the concentration will be accompanied by a doublingof the amount of iight absorbed, and therefore a doubling of theactual quantity of substance decomposed.I n this case the rate ofdecompositicn is proportional to the concentration of the solutdon,which is expressed by the equation f o r a unimolecular reactiondx/dt==k(a-z). These conditions were found t o be satisfied by* The comparison mentioned refers to the efiects produced by the other lines iuall cases on solutions initially of approximately the same composition, namely,0-075NHYPOCHLORITE SOLUTIOSS. PART 11. 2575the line ~ 4 0 5 (which is only slightly absorbed), as the followingresults show :Expt . Ic). Initial concentration ofsodium hypochlorite = 0.076N(approx. 1Tim;in,hours. Titre. k.0.0 37.81 -1.7 37-21 0.0041 22.3 37.02 4002.8 36.85 0.00400Expt. (,d). Initial concentration ofsodium hypochlorite=O-Ol3.Vapprox.)./- A\ Timeinhours.Titre. k.0.0 6.71 -1.5 6.63 0.003473.4 6.51 3824.2 6.46 3945.1 6.39 0.004 12Although the constant in experiment (d) is not' particularly goodi t is not very different in value from that of experiment ( c ) , thatis, the constant is independent of the absolute concentration. 111experiment ( c ) t h e change in the titration vaIue is of the order0.35 C.C. per hour as a mean, whilst in (d), the weaker solution, therate is approximately 0.063 C.C. per hour. A comparison withexperiments ( a ) and ( b ) illustrates the difference in behaviour inthe two cases. These results are in agreement with Luther's" absorption " thetory of the velocity of photochemical reactions.The gradu'al rise of the unimolecular constant with time observe(*when water only occupied the filter space is now explicable.Thelight' from the lamp can be considered as made up of tlwo sets oflines, the' short wave-lengths which are weak in intensity but arestrongly absorbed by the given thickness of solution, and the longwave-lengths of higher intensity, but weakly absorbed by the samethickness of solution. The effect of the long waves is greatest in astrong solution, but rapidly falls off (compare the line ~ 4 0 5 above).On the other hand, the effect, of the short waves is fairly constantthroughout. With both together the long waves are predominanta t the outset, and their action is fairly well represented by theunimolecular formula d z / d t = Ic(a - x).As the solution becomesmore dilute, however, the short wave-lengths become more impor-tant, with the consequence that the value of the unimolecular" constant " begins t o rise sinc3 their effect' approximates t o thecase of the line A 313, where d x l d t = Ic rather than dxldt =7i(a - x)expresses the reaction.A'ote O I L the Iiifluence of Light on, the Bleaching of Lii~enby Sodium Hypochlorite.Two bands of opaque paper welre fastened 3 cm. apart round theuviol lamp, which was enclosed in a uviol glass sheath. This wasimmersed in a jar of the hypochlorite solution, and a piece ofunbleached linen was placed loosely around the lamp. After a2576 PHOTOKINETICS OF SODIUM HYPOCHLORITE SOLUTIONSexposure of one to two hours, the portions of the linen exposedto the rays from thel lamp were1 found to’ be slightly more bleachedthan the parts in the shadow.The light had therefore slightlyaccelerated the bleaching action.Summary.(1) The further investigation of the1 kinetics of the reactionNaClO+NaCl+O, using the mercury uviol lamp, has beencarried out.(2) By employing Winther’s and Plot’nikov’s filters variousspectral regions have been examined and the relative photoclzemicalefficiencies of these regions determined.(3) The results are in favour of Luther’s absorption theory ofphotochemical action. The general reaction equation may bewrittenFor monochromatic light when the absorption-coefficient m is smallthe above equation reduces to dx/dt =constant x (a - x), that is,apparently unimoleculm ; when the absorption-coefficient m is largethe equation reduces t o d x / d t =constant, that is, a “zero niole-cular ” equation. These: relations have been verified in the caseof the’ lines I 405 and A 313 respectively.(4) The temperat’ure-coefficient has been measured, and like themajority of photo-reactions is small.(5) When the photo-effects are reduced to one and the sameintensity for the various lines i t is shown that the shorter thewave-length the more effective is the decomposition, that is, thegreater the velocity constant. Under actual conditions, however,the intensity of the lines differs with the result that 1366 is moreeffective than ~ 3 1 3 . The latter is the shortest strong line measur-able with the uviol lamp. The head of the absorption band ofsodium hypochlorite lies beyond this. Shorter lines will thereforebe investigated with the help of quartz apparatus.(6) It has been found that the presence of light from the uviollamp slightly accelerates the bleaching of linen by sodium hypo-chlorite.I n conclusion,. the author wishes t o express his thanks t oProfessor W. C. McC. Lewis for suggesting and supervising theresearch.‘THE MUSPRATT LIRORATORY OF PHYSICAL A S D ~ 1 , 1 2 C . ~ ~ O - C t I l ~ ~ I I S ’ I . R Y ,THE UNWEKSI I‘Y OF LIVEP.POUL

ISSN:0368-1645    

DOI:10.1039/CT9140502565

出版商:RSC    

年代:1914

数据来源: RSC

摘要:

INTERNATIOSAL ATOMIC WEIGHTS. 2577THE Council has ordered Lhe following letter and report to beprinted in the Journal and Proceedings of the Society :WHINFIELD,SALCOMBE,S. DEVON.Seyt. 18tJb, 1914.GENTLEMEN,I have! the honour to forward the Annual Report of tileInternational Committee on Atomic Weights for 1915, which issubmitted for publication in the Society's Transactions and Proceed-ings, as hitherto. Some delay has occurred in presenting it owingto the disturbance of the postal arrangements on the Continent inconsequence of the war, and to the illness of Professor Urbain.The Report deals witlfh all the determinations of atomic weightswhich have been published since the issue of the preceding Report;but, ia accordance with the resolution of the Eighth InternationalCongress of Applied Chemistry, no change in the official table ofatomic weights will be made until after the meeting of the nextCongress.It is recommended, therefore, that the table accompany-ing the Report for 1913 should be reprinted without alteration.I have appended the signatures of Pirofessors Ostwald andUrbain as desired by thein, subject to a qualification by the latterwhich lie proposes t o introduce in the French translation of theReport in connexion with t h e atomic weights of Ytterbium andLutecium.I am, Gentlemen,Your obedient Servant,T. E. THORPE.The Hoiz. Secretarzes,The Chemical Society,Lon don.Annual Itepor t of the International Committee on AtomicWeights, 1915.The Council of the International Association of Chemical Socie-ties, with which the Committee on Atomic Weights is nowaffiliated, recommended, a t its meeting in Septlember, 1913, thatthe annual report of said committee should be published inAugust.The present report, therefore, is submitted in compliancewith that recommendation, although delays due to the diEcu1tie.2578 ANNUAL REPORT OF THE INTERNATIONALof correspondence may sometimw prevent simultaneous publica-tion in all countries.Since the report for 1914 was prepared, a number of new atomic-weight determinations have been published. These may be brieflysummarised as follows :Silver, Sulphur and Chlorine.-Scheuer (Arch. Sci. phys. ?iut.,1913, [iv], 36, 381) dissolved pure silver in sulphuric acid, andcollected and weighed the sulphur dioxide given off.The weighedsulphate was then converted into chloride by heating in a currentof gaseous hydrochloric acid. Three ratios were thus determined,which gave the three desired atomic weights, independent’ of allformer determinations. The results obtained are Ag = 107.884,S=32*067, C1=35*460. The value f o r silver is rather high; theother values agree with those generally accepted.CcrZciuin.-CEchsner de Coninck (BulZ. L4~crd. roy. Belg., 1913,222) has determined the atomic weight of calcium by conversionof the carbonate into the sulphate. His final value is Ca=40.13.Barium.-Also redetermined by CEchsner de Coninck (Re P . yCii.chin). p i r e crppl., 1913, 16, 245). Barium carbonatle was dissolvedin nitric acid, and the carbon dioxide so evolved was weighed.The value found was Ba = 137.36.Copper.-Atomic weight determined by 03clisner de Coninckand Ducelliez (Rec;. g t ~ .chim. pure app!., 1913, 16, 122). Copperwas oxidised by nitric acid, and the oxide was weighed, I n fiveexperiments they found Cu=63.523 t o 63.605; in mean, 63.549.These atomic-weight determinations by CEchsner de Coninck arepublished in the briefest possible way, without’ any of the detailsthat are commonly regarded as essential. How were the substancespurified?Cadmium.-Quinn and Hulett ( J . Physicnl Chenz., 1913, 17,780) have redet’ermined the atomic weight of cadmium by electro-lysis of the chloride and bromide. I n each series the cadmium wascollected and weighed in mercury.From the chloride, withC1= 35.458, Cd = 112.32. From the bromide, with Br = 79-92,Cd = 11 2.26. These values agree well with those previously foundby Perdue and Hulett, and by Laird and Hulett, butl are muchlowelr than the value (Baxter’s) adopted in the table. The causeof the difference is yet t o be satisfactorily explained, but i t mustbe due to a constant error in one or the other of the inethodsemployed. A change in the table would be premature.i1fercury.-Taylor and Hulett ( J . I’kysicccl Chem., 1913, 17,755) prepared mercuric oxide by heating pure mercury in oxygen.Weighed amounts of the oxide were then decomposed by heatingit with metallic iron, and the mercury was collected and weighed.Were the weights reduced t o a vacuumCOMMITTEE ON ATOMIC WEIGHTS, 1915.2579From the data thus obtained, Hg=200*37. This, as in the case ofcadmium, is lower than the recognised value, and its acceptance orrejection must await further evidence.T'ntzadium.-Atomic weight redetermined by Briscoe and Little(P., 1914, 30, 64; T., 1914, 105, 1310) from analyses of theoxychloride, VOC1,. The) mean value found was V=50-950 but50.96 is preferred.Srlet2iLini.-Jannek and Meyer (Zfitsch. nizorg. C'henz., 1913, 83,51) determined the atomic weight, of' selenium by oxidising Se toSeO,.The same constant was deduced by Bruylants and Bytebier(UiiZI. AccxZ. roy. Belg., 1912, 856) from the density of seleniumhydride, SeH,. I n four series of experiments, the weight of alitre) of the gas a t Oo and 760 mm.was found t o be 3.6715 grams.For the weight of a litre of oxygen under the same conditions theyfound 1.4295 grams." By the method of limiting densities, andwith H=l.008, Se=79.18, which is near the value given in thetable.TeZ1ziriicm.-Dennis and Anderson ( J . A Trier. C'liem. Soc., 1914,36, 882) purified tellurium by preparing the hydride, TeH,, fromaluminium telluride, and condensing t h e gas to solid a t thetemperature of liquid air. From the hydride the metal wasobtained by heating t o 500O. Thirty-one conversions of Te thusprepared into TeO, gave in mean Te=127.6. Other determina-tions by a volumetric method gave a lower value, near 127.50.The authors conclude t h a t the higher, hypothetical " dvitellurium "does not exist.Scntzdium.-Lukens ( J .A mer. Chem. Soc., 1913, 35, 1470) pre-pared scandium oxide from Colorado wolfram. By calcination ofthe sulphate to oxide he found Sc=44.59 and 44.77. The materialwas probably not quite pure.Y ttrizcn1.-Meyer and Weinheber (Ber., 1913, 46, 2672), byconversion of yttrium oxidel into sulphate, found Yt = 88-75. Bythe reverse process they found Yt =88*74. Corrected t o a vacuum,this becomes 88.70.Ytterbium and Lutetium.-Atomic weights reinvestigated byAuer von Welsbach (iUor~ntsh., 1913, 34, 1713). For ytterbium(aldebaranium) he found Yb = 173.00. For lutecium (cassiopeium),LU = 175'00.Iridium .-Holzmann (Sit z un p b e r . phys.-m en. Soz. Edangeiz,44, 84) made four reductions of the salt' (NHJ21rCl6 in hydrogen,and found Ir=193*42.This is higher than the accepted value,and not conclusive enough to justify a change.weighs 1.42900 gram?.The mean of ten experiments gave Se= 79.140.* Accoicling to Geiman (Compt. wnd., 1913, 157, Y26), the norinal litreof oxygr2580 ANNUAL REPORT OF THE INTERNATIONALHelium.--Heuse (Ber. Deut. physilial. Ges., 1913, 15, 578), inseven determinations of the density of helium, finds the weight ofa normal litre to be 0.17856 gram. Hence, by the method oflimiting densities, He = 4.002.Neon.-From two determinations of the density of neon, Leduc(Compt. rend., 1914, 158, 864) finds Ne=20.No changes of serious importance seem to be needed in theatomic-weight table. Possibly the values for yttrium, ytterbium,helium, and neon should be changed, but such action may well bedeferred until next year.Some experiments by Richards and Cox( J . Amer. Chem. SOC., 1914, 36, 819) on the purity of lithiumperchlorate also suggest a possible lowering in the atomic weightof silver, namely, from 107.88 to 107.871.(Signed) F. \IT. CLARKE.W. OSTWALD.T. E. THORPE.G. URBAIN.NoTE.-since this report was finished and approved, ProfeaqorUrbain has informed us that, jointly with M. Blumenfeld, he hasre-determined the atomic weight of neoytterbium with great care.The earth was subjected to many fractionations, and each fractionwas stndied magnetically and spectroscopically. The value foundfor the atomic, t-he mean of thirteen determinations, was 173.50.He suspects that the ‘‘ aldebaranium ” studied by Auer von Wels-bach contained an element of lower atomic weight, probablythulium, Urbain’s paper will be published in the near future,perhaps before this repor’c appears. F.W. C.T. E. TCOMMITTEE ON ATOMIC WEIGHTS. 1915 .1915 .Internutionat Atomic Weights .Aluminium ................. A1Antimony ..................... SbArgon ...................... AArsenic ..................... AsBarium ........................ BaBismuth ..................... BiBoron ........................ EBromine .................... BrCadmium ..................... CdCaesiuin ...................... CsCalcium ..................... CaCarbon ........................ CCerium ........................ CeChlorine .....................C1Chromium .................. CrCobalt ....................... CoColumbium ................. CbCopper ........................ CuErbium ..................... ErEuropium ..................... EuFluorine ..................... FGadolinium .................. GdGallium .................... GaGermanium .................. GeGlucinum .................... G1Gold ........................... AuHelium ........................ HeHolmium ..................... HoHydrogen ..................... HIndium ....................... InIodine ........................ IIridium ....................... I rIron ........................... FeKrypton ..................... KrLanthanum ................. LaLead ......................... PbLithium ....................LiLutecium ................... LuManganw .................. Mn................. Dysprosium DY.................. Magnesium MgMercury Hg .....................0 = 16 .27.1120.239.8874.96137-37208.011.079.92112'40132.8140.0712-00140'2535 '4652 '058-9793'563.57162.5167.7152.019'0157.369.972 '59 *1197.23-99163.51 '008114.8126.92193.155-8482.92139.0207.106 '94174'024-3254-93200'62581Molybdenum ............... MoNeon ........................... NeNickel ........................ NiNiton (radium emanation) NtNitrogen ..................... NOsmium ..................... 0 sOxygen ........................ 0Palladium., ................... PdPhosphoriis ..................PPlatinum ..................... 19Potassium ..................... I<Praseodymium ............... PrRadium ........................ KaRhodium .................... BhRubidium .................... RbRu then iu 1 n .................. RuSamarium ................. SaScandium ................... ScSelenium ..................... SeSilicon ........................ SiSodium ........................ NaStrontium .................. SrSulphur ..................... STantalum ................. TaTellurium ..................... TeTerbium ..................... TbThallium .................... TIThorium ..................... ThThulium ..................... 'I'mTin ........................... SnTitanium ..................... TiTungsten ..................... WUranium ..................... UVanadium .................. VXenon ........................ XeYtterbium (Neoytterbium) Y bYttrium ..................... YtZinc ........................... ZnZirconium ................... ZrNeodymium ................. Nd........................ Silver Ag0 = 16 .96. 0144.320.258-68222 '414'01190.916.00106.731 '04195'239'10140.6226 '4102'9101.7150'444-179.228.3107.8823.0087 '6322-0785.45181'5127.5159.2204.0232'4168'5119'048*1184.0238 '551'0130.2172.089.065.3790.6VOL . cv . 8

ISSN:0368-1645    

DOI:10.1039/CT9140502577

出版商:RSC    

年代:1914

数据来源: RSC

摘要:

2582 SHRODER ANn ACtlEE: CATALYSIS. PART XVIII.CCXL.-Catalysis. Part X V l II.* The &actions ofBoth the h i s and the Molecules of Acids,Buses ccnd Salts: The Reactions of Alkyl Haloidswith Phenoxides and Bthoxides.By JOHN HANSTON SHRODER and SOLOMON FARLEY ACREE.THE two recent papers by Segaller (T., 1913, 103, 1154, 1421) cnthe action of alkyl haloids on sodium phenoxide show that thereaction-velocity increases with dilution, the formulaK,=K,+alog V ,used by Hecht, Conrad, and Briickner (Zeitsch. physikal. Chem.,1890, 5, 289), applying equally well t’o Segaller’s results. Eversince the brilliant work of Arrhenius on the ionic theory, and ofOstwald on the relation between the ionisation of acids and theiractivity in ester catalysis, inversion of sucrose and hydrolysis ofacetamide, chemists generally, Kahlenberg ( J .Physical Chem.,1901, 5, 339; 1902, 6, 1) especially, Michael (Amer. Chem. J.,1910, 43, 322) and Armstrong being notable exceptions, havebelieved that only ions enter appreciably into chemical transforma-tions. Even the known “ deviations from the ionic reactions,”especially those produced by added salts, were thought t o be dueto a change in the ionic reaction by the salts themselves. As itwas pure chance that Arrhenius and Ostwald worked with reactionsin which ions are chiefly concerned, and as the “deviation fromthe ionic reaction ” or “ salt catalysis ” observed by them couldbe partly or wholly due t o the reactions of the non-ionised electro-lytes, the workers in this laboratory have since 1905 been usingthe theory that both the ions and molecules of acids, bases andsalts, must in all cases be examined f o r activity. Johnson andAcree in 1907 (Amer.Chem. J . , 37, 410; 38, 258) brought outthis idea clearly f o r salts, and in 1908 Shadinger and Acree wrote :“ We are studying the problem whether acids, bases and salts enterinto these reactions through their ions o r molecules, or both.”Besides the discussion of “salt catalysis” (ibid., 1908, 39, 230),we gave the equation (ibid., p. 228) dxldt =KtrnllSa(A -z>2 for thereactions of the ions, as Arrhenius, Ostwald, and all others sincethem have done, and then gave (ibid., p. 228) the equationiEx/dt = X’tr:L,,s (1 - a ) ( A - z)2 for the activity of the “ undissociatedacid, base o r salt,” this idea and equation being the first newcontribution t o the theory of chemical reactions and the cause of* For references t o the earlier papex see dmer.Chem. J., 1913, 49, 474SHRODER AND ACREE: CATALYSIS. PART XVIII. 2583the ‘( deviations from the ionic reactions I’ or “ salt catalysis ” sinceArrhenius’ brilliant work in 1885. Before the American ChemicalSociety in Baltimore, in December, 1908 (Scieme, 30, 624), oneof us stated that: (‘We see, then, that the question whether theanion or cation (simple or complex) or the molecular form of agiven acid, base, salt or other neutral substance, is the chief con-stituent transformed directdy into the end products dependsentirely upon the relative magnitudes of the various constants, andtherefore varies widely in the different problems.” Our work(,4mer.Chem. J . , 1912, 48, 352; 1913, 49, 116, 127, 345, 369, 474,and earlier papers) has now shown that this new idea of theactivity of non-ionised electxolytes is fully as important forchemical reactions as the idea that ions are active. To expressreaction-velocities completely, we must use the equationK , =‘[liia + K ?n (1 - a> ][I + (f>c.&1tI.The second term on the right side of the equation represents afactor for “salt catalysis,” and the first term gives the activity ofthe ions and molecules in normal solutions having the ionisationa and the velocity X,. This theory has been found t o hold inabout thirty reactions studied by us in concent’rated solutions( N / l t o N/32), as well as in ideal solutions ( N / 3 2 t o N/2048), thework involving the three most important classes of chemicalchanges, namely, metathesis, pure catalysis and intramolecularrearrangement.By this theory we have been able to reinterpretthe older work of Arrhenius, Ostwald, Conrad and his co-workers,Koelichen, Tubandt, Stieglitz, Bredig, Goldschmidt, Holmberg,Senter, Walker, van Dam, Blanksma and Segaller as reactions ofboth ions and molecules, instead of ions alone. The theory has,furthermore, now been accepted and used by Arrhenius (Taylorand Arrhenius, Medd. X. Vetenskapakad. Nobelinst., 1913, 2,Nos. 34, 35, 37), Stieglitz ( J . Amer. Chem. Soc., 1912, 34, 1687,1688, 1689, 1690, 1694; 1913, 35, 1774), Dawson (T., 1913, 103,2135 ; this vol., p.1093), Goldsclimidt (Zeitsch. Elektrochezm., 1909,15, 6 ; Zeitsck. physikal. Chcm., 1910, 70, 627), Bredig (Zeitsch.Elektrochem., 1912, 18, 535, 543 ; Zeitsch. physikal. Chem.,1913, 85, 129, 170, 211), IIolmberg (Zeitsch. physikal. Chem.,1913, 84, 451, 468; 469), Biddle ( J . Amer. Chem. SOC., 1914, 36,99, and earlier papers), Kilpi (Zeitsch. plqsikal. Chem., 1913, 86,427, 644), and Worley (Phil. Mug., 1914, ‘[vi], 27, 459), and bidsfair t’o become generally useful in all reactions involvingelectrolytes.Segaller ‘studied the reactions of N / 2-sodium phenoxide with anumber of different alkyl haloids a t 42‘5O in order to measuretheir relative chemical activities. Fortunately, he investigated the8 F 2584 SHEZODER AND ACREE: CATALYSIS.PART XVIII.action of Ii-propyl iodide OIL varying concentrations of sodiumphenoxide, and it is this work that interests us a t present, as i textends our series of investigations with methyl and ethyl iodidesa t 2 5 O and 3 5 O . Lack of time alone is all that has prevented usfrom using all the other alkyl haloids in our work on the phen-oxides, ethoxides, and urazoles. We have now extrapolatedSegaller’s data to obtain the reaction-velocities for solutions exactlyN / 2 , N/4, i V / l O , and N / 2 0 , and have found by the use of ourequation, K , = Kia + Em(1 - a), that his data harmonise excellentlywith ours and with our theory, both the phenoxide ions and thenon-ionised sodium phenoxidc seeming to react with )+propyliodide, as follows :C,H71 + OC6H, -+- C,H7*O*C,H, + I ;C,H,I + Na0*C6H5 + C,H,*O*C,H, + NaI.The following tables show the values of K’, and Arm obtained byus from our own work on methyl and ethyl iodides and sodium,potassium, and lithium phenoxidea at1 2 5 O and 3 5 O , and fromSegaller’s work at 42’5O.Because of larger experimental errors,the values of Ki do not agree as well a t 3 5 O as a t 25O. The valuesof a used by us in recalculating Segaller’s data were obtained byextrapolation of H. C. Robertson’s data f o r sodium phenoxide a tOo, 2 5 O , and 3 5 O . It is seen that the ratio Ki/Iim for both methyliodide and ethyl iodide and sodium phenoxide is from 5 to 6 a t 2 5 Oand 6 to 7 a t 3 5 O , whilst f o r propyl iodide it is about 17 a t 4 2 * 5 O ,and the reaction is almost purely ionic in solutions more dilutethan N/50. The value for Iii for the phenoxide ion and methyliodide is about five times as large a t 2 5 O and 3 5 O as that forethyl iodide, which in turn is about three times the value for Kifound for the phenoxide ion and propyl iodide a t 42’5O.Temperature, 25O.Sodium phenoxide and methyl iodide .. .Sodium phenoxide and ethyl iodidePotassium ,, y 7 Y9 3 , 0 . . Lithium , Y ?, Y , 7, .*.Potassium ,, Y ? 1 , Y Y * * .Lith4um ,, 93 Y , 9 9...Temperature, 3 5 O .Sodium phenoxide and methyl iodide . . .Potassium 7 y 7 ) 7 7 Sodium phenoxide and ethyl iod%e ...Potassium ,, 3, 2 , Y7 Lithium ), Y 9 2 9 7 7 *.....Temper a tare, 4 2 * 5 O .Sodium phenoxide and propyl iodide ...Ki.0.02820.02830.02870.005510.005 180.005340.09090.10360.01830.01970.01740.0128K,.0.004770.003700.003930.0009870~0010110.0009 100.013 100.009830.003 2 30-002700.003190*00075SHRODER AND ACREE: CATALYSIS.PART XVIII. 2585Our chief interest in Segaller’s work and that of Hecht, Conrad,and Bruckner lies in the fact that the change in K , with dilutionfollows the equation K,=K1+a log V , as written by Hecht,Conrad, and Briickner.KIN - Ii, =a log ( V f / V ) ,in which K f , and K , represent V / K v , and V K v , the reaction-velocities for the concent’rations 1/V’ and l l V , as used in ourformer papers. This equation is purely empirical, has never beengiven any scientific foundation, and it does not involve the chang-ing ionisation of the ethoxide, or phenoxide, because Hecht,Conrad, and Briickner did not consider the possibility of theionisation of the sodium etlioxide or phenoside, but spoke of allthese substances as non-electrolytes, or “ nichtleitende Korper.”We have therefore interested ourselves in determining why thissimple equation holds so excellently, as it, undoubtedly does, forall the work of Hecht, Conrad, and Briickner, Segaller, and forthat part of ours to which we have applied it.When we write Conrad’s equation as (1) ZI, - K , =a log (1’1 / Ti),and two of our simultaneous equations as (2) K , = Kia + K,(I - a )and (3) KIN= Kia/+ K,(I - a/), and subtract (2) from (3), we get(4) K / , - K , = ( K i - K,) (a1 - a ) .By comparing equations (2) and(4) we get (5) KIN - K , :=u log ( V / / V ) = ( K i - Km)(u’ - a), andA more general form isn log (Vl/ V ) of Conrad’s equation (I) has a scientific basis, there-fore, only if equation (6) actually gives “constants” f o r n. Wehave recalculated Segaller’s work, and Dr. W. A. Taylor has thatof Hecht,, Conrad, and Briickner, and we have also applied theseequations to much of our own work; we find that equations (6)and (7) hold excellently within the experimental errors. O€course, the central point hinges on the validity of the relation#= K, an empirical equat’ion t,liat holds very well in the a - alog ( ul/ P)mire concentrated solutions of a number of electrolytes t o whichwe have! applied it, whether the electrolyte obeys the Ostwalddilution law or is too ‘‘ strong ” to do so.This equation cannothold for all concentrations, because the ratio V1/V keeps onincreasing after complete ionisation is reached, whereas a/ - a thenremains constant.. We are investigating all these relations fully,and extended reports on the work of Segaller, and of Hecht,Conrad, and Briickner, will soon be published by Dr. J. H. Shroderand Dr. W. A. Taylor.It is seen in tables VI of both sections of the experimental por-tion that both equations (6) and (7) give very good constants fo2586 SHRODEE AND ACREE: CATALYSIS. PART XVIII.a, the two values, 0.00265 and 0*00269, for sodium phenoxide andpropyl iodide a t 42’5O agreeing better than the values 0.0247 and0.02594 for sodium ethoxide and methyl iodide a t 24O.It is seenin tables VII of both sections that the values for (I K , calculated ”agree well with those for (( XN found.”It is thus seen that the empirical relationK‘, - KN = a log ( v// v)used by Hecht, Conrad, and Briickner, and by Segaller, and therelation KIN= ITN observed by Bredig (Zeitsch. iTleklrochem., 1904,10, 582),, Tubandt (Annalen, 1905, 339, 41 ; 1907, 354, 259;1910, 377, 284), Steger (Rec. trau. chim., 1899, 18, 13, 41), andby McCombie and Scarborough (this vol., p. 1304), and Myers andAcree (Amer. Chem. J., 1912, 48, 358; 1913, 49, 144, 3671, andthe salt-catalysis equation, K , = X , a + K,a2, or its equivalent, usedby Arrhenius, Spohr, Euler, Stlieglitz and others, are all specialcases that can be converted into our general equationinvolving the reactions of both the ions and the non-ionised formsof acids, bases, and salts.K , =’[&a + Km( 1 - 4[1+ (f)Q,,,,],Imteraction of Sodium Phenoxide and Prop$ Iodide at 42.5O.TABLE I,K, Found for Sodium Phenoxide and Propyl Iodide at 42’5O.Concentrationof sodiumphenoxide.V .K,. K , average.2 0.002800.002930.003050.00309 0.002974 0.003690.00371 0.00370Concentrationof sodiumphenoxide.V . K,. K , average.10 0.0048020 0.005520.00475 0.004780.00571 0,00562TABLE 11.Ionisation of Sodium Phenoxide at 42.5’.V . a. l-a.2 0.1826 0.81744 0.2400 0.760010 0.3265 0.673520 0.4065 0.593SHRODER AND ACREE: CATALYSIS. PART XVIII.2587TABLE 111.Ki and I<, Found for Sodium Phenoxide and Propyl Iodidea,t 42*5O.Ki.v=2 : v = 4 0.0 13 37v=2 : v=10 0.01325v = 2 : v=20 0.01264 v=4 : v=10 0.0 13 19v=4: v=20 0.0 1246v=10: v=20 0.01185Km.0.0006480.0006730~0008090.0007040.0009320*001364*Average 0.01280* This value was omitted.0.000753TABLE IV.K, Calculated and Found for Sodium Yhenoxide and PropylIodide at 42’5O.V. K,. K, calculated. Error, per cent.2 0.00297 0.00295 + 0.74 0.00370 0.00364 + 1.610 0.00478 0.00469 + 1.920 0.00562 0.00565 - 0.5. TABLE V.Per Cent. of Reaction Due to Ions and to Molecules.Concentration ofsodium phenoxide Per cent. of reaction Per cent. of reactionV. due to a K;.due to (1 -a)&.2 79-14 20.864 84-40 15-6010 89-10 10.9020 92.09 7.91TABLE VI.a ” Found for Sodium Phenoxide and Prom1 Iodide at 42.5O.a=- K’, - K , (Ki-Km) ( ~ ’ - a ) .log( V‘/V)’ a = 1% ( V’/ V )v = 2 : v = 4 0.002425 0.002297v = 2 : v=10 0.002589 0.0024801.‘-2: TTZT20 0*002650 0.002698v-4: v-10 O.0027 13 0.008G18J’Z4 : 1’-20 0.002746 0.002870T’710 : v=20 0.002789 0.003205Average 0.00265 0.00262588 SHRODER AND ACREE: CATALYSIS. PART XVIIT.sodium ethoxide K,.1 0.055122 0.062766 0.07 18210 0.07950sodium ethoxide Kh .20 0.0869640 0.0944880 0.1022v.TI= 1 : v = 2 v = 1 : v= 5 v = l : V = l OV= 1 : v = 2 0V= 1 : V=4OV= 1: V=80 v = 2 : v = 5V= 2 : v=10 v = 2 : V=20V== 2 : V=40 v = 2 : V=80V= 5 : V=10V= 5 : V=20V= 5 : V=40V= 5 : V=80V=10: v=20V=10: V=40v=10 : V=80V=2O: V=40V=20: V=80T7=40 : V-801 0.1470 0.85302 0.2346 0.76545 0.3336 0.666510 0.4170 0.5830Average20 0.5075 0.492540 0.6040 0-396080 0.7030 0,2970Ki.0.12940,12150.13120.13040-12840.12740-13280.13300- 13060.12810.12730.13310.12970.12760.12670.12750.12620.12580.12530.12550- 12560.1287-__K*.0.042300.04 1940.041840.042 120.042440.042640.041260.041220.04 1940.042600.042960.041140.042800.043860.044340.045100.046080,046300.047400.047260.04 7 000.0435SHRODER AND AGREE: CATALYSIS.PART XVIII. 2589TABLE IVK, Calculated and Fozcnd for Sodium Ethoxide and MethylIodide at 24O.K,.Error in v. K,. calculated. per cent.1 0.05512 0.05605 -1.682 0.06276 0.06352 -1.215 0.07182 0.07194 -0.1610 0.07950 0.07905 +0*57K,. Error inV . K,. calculated. percent.20 0.08696 0-08676 +0*2380 0.1022 0.1034 -1.1740 0.09448 0.09498 -0.52TABLE V.Per Cent. of Bectctiorh Due t o Ions and to Molecules.Concentra-tion of (sodiumethoxide.12510Per cent.If reactiondue toaKi.33.7547.5369-6667.89Per cent.of reactiondue to(1 - a)Kn.66.2552-4740-3432.11Concentra- Per cent. Per cent!tionof of reaction of reactionsodium due to due toethoxide. &Ki. (1 - a)K,.20 75-28 24.7240 81.84 18-1680 87.51 12-49TABLE VI.( ( a ’ 7 Found for Sodi~unz Ethoxide and Methyl Iodide a t 24’.a =v = 1 : V= 2 v = 1: V= 5V= 1 : V=lO v = 1 : V=20V= 1 : V=40V= 1 : V=80V= 2 : v= 5 v= 2 : V=10 v = 2 : V=20T i = 2 : V=40V= 2 : V=80 v= 5 : V=lO v= 5 : V=20V= 5 : V=40V= 5 : V=80V=10: V=20V=lO: V=40 “ = l o : v=soV=20: V=40V=20: V=80V=40: V=80K’, - K ,l O g ( V ) ‘ a0.025380.023880.024380.024470.024560.024740.022760.023930.024200.024380.024310.0255 10.025 150.025090.045230.024780.024880.025 130.024980-025310.025640.024780.0227 10.022990.023590.028510.029210.021160.022210.027290.028370.029230.023280.024610.025500.026220.025600.029440.026970-027300- 0 2 7 6 80.02800Average 0.02470 0.02592590 SHRODEK AND ACREE: CATALYSIS.PART xvm.TABLE VII.KN Pound, K, Calculated fobtained by using a ” in the EquationK‘N=K, + a log (V/V)], and Percentage Error.K NV , found.1 0.055122 0.0627 65 0.071820.0795020 lo 0.0869640 0.0944880 0.10220K , calculatedfora= 0.02470.0.054580.06 1990.071820.079480.086690.094120.10 159Error,per cent.+ 0.99 + 1-24 + 0.00 + 0.03f0.31 + 0.36 + 0-59K , calculatedfora = 0.02594.0.053720.061500.071820.079630.087430.095240.10305Error,per cent. + 2-60 + 2.010.00-0.16- 0.54- 0.79- 0.81Conclusions.(1) It has been shown that the work of Hecht:, Conrad, andBriickner on the interaction of methyl iodide and sodium ethoxidea t 24O, and that of Segaller on t4he inbradion of n-propyl iodideand sodium phenoxide a t 42*5O, harmonises with our own workalong these lines. Their data give constants for X i and K , whensubstituted in the equation KN =Ria + K,(1- a), and furnishexcellent evidence that both the ethoxide and phenoxide anions, aswell as the non-ionised sodium ethoxide and sodium phenoxidemolecules, react with the alkyl haloids. The values Ri=0.1287and Rm=O.O4354 are found for methyl iodide and sodium ethoxideat 24O, whereas Ki=0*0128 and R,=0*000753 are found forsodium phenoxide and propyl iodide a t 42.5O.(2) Hecht, Conrad, and Bruckner, and Segaller, found that thereaction-velocitim can be expressed accurately by the equationK’N=KN + a log (TI/ V ) , an equation which does not lake into con-sideration the changing values of the ionisation of the ethoxidesand phenoxides. We have found that this equation harmoniseswith our theory and the equation KN = Kia + K,(l - a), becauseof the fact that the changes in volume, ionisation, and reaction-velocity correspond closely with t-he equationsWe are indebted to the Carnegie Institution of Washington foraid in this work.JOHNS HOPKINS UNIVERSITY,BALTIMORE, MD

ISSN:0368-1645    

DOI:10.1039/CT9140502582

出版商:RSC    

年代:1914

数据来源: RSC

摘要:

INFL4MMABILTTY OF MIXTURES OF METHANE AND AIR 2591CCXLL-The Limits of Iri$arnmability of Mixturesof Methane and Air.By MAURICE JOHN BURGESS and RICHARD VERNON WHEELER.IN a recent communication (this vol., p. 1859) Coward and Brinsleysuggested that “inflammability mustl be regarded as a specificproperty, either present or absent; of any given gaseous mixtureunder definite conditions of temperature and pressure ” (p. 1884) ;(( independent of the shape and size of the vessel containing it, andindependent also of the nature of the means used for ignition inthe first place” (p. 1861).On the basis of this definition, a ‘(criterion” of inflammabilitywas put forward, which, stated briefly, demands that the true‘( limit-mixtare” must be regarded as that’ in which flame can bepropagated upwards-indefinitely.It is well known that mixtures of methane, for example, and airhave different.limits of inflammability, both higher and lower,dependent on the direction in which the flame has to travel.*Coward and Brinsley were probably led to their choice as t o whatconstitutes a true ( ( limit-mixture ” by consideration of the factthat a smaller percentage of inflammable gas is required (theydeal only with the lower-limit) for upward than f o r downwardpropagation of flame, and by the belief that the experimental condi-tions specified by them disclosed the least quantities of the com-bustible gases, hydrogen, methane, and carbon monoxide, that arecapable of forming with air mixtures in which self-propagation offlame can take place.It does not seem t o us desirable so t o restrict the use of the term‘( limit-mixtu.re.” The most important industry in which knowledgeof the limits of inflammability of gaseous mixtures is required iscoal-mining. The occurrence of firsdamp in mines constitutes, asis well known, one of the gravest dangers t o the industry; not somilch, i t is Selieved, because of the possibility of widespread explo-sions taking place in firedamp and air mixtures extending through-out the workings, modern legislation regarding the ventilation ofmines having rendered such occurrences exceedingly unlikely, butbecause a local accumulation of fire-damp, forming an explosivemixture with the air, may become ignited and transmit flame t o* This fact has been empliasised by Professor Enriqiie Hauser in a brochureentitled “ Leqons sur le grisou ” (Madrid, 1908).Hmser has summarised thedifferent results given by various experimenters for thc limits of inflammability ofmethane-air mixtures, and has offered an explanation of the differences2592 BURGESS AND WHEELER: THE LIMITS OFany fine coal dust that may be deposited on the roadways, and soproduce a widespread coal-dust explosion.Legislation has attempted to deal also with this danger, bystipulating that frequent analyses shall be made of the air of themine roadways and workings, and precautions taken t o preventthe percentage of methane contained in the air from exceeding acertain minimum. Despite precautions, accumulations of fire-damp,usually near the roof, sometimes occur; and, should sufficient fire-damp mingle with the ventilating current and by some mischanceencounter a sufficiently intense source of heat, what is te-chnicallycalled a “local ignition ” may occur.I n the majority of casesno’ damage or loss of life is caused by these “local ignitions,”which usually takc the form of a slowly-moving flame near theroof.Such cases of the propagation of flame in fire-damp-air mixturesare those moat freque’ntly reported. It will be realised that thedanger lies in the existence, over a considerable length of roadway,of a mixture in which a flame can travel horizontally. A similardanger arises when, as has been known t o happen, a fall of partof the roof liberates, and distributes in the ventilating-current, aquantity of fire-damp that has accumulated in cavities above theroof.,4 uniform inflammable mixture of fire-damp and air rarelyoccurs throughout any considerable area of a coal mine, but thereis an instance when a disused heading (or cul-de-sac), in which theair was practically stagnant, was slowly fed with fire-damp issuingfrom the neighbouring strata until, when the fact was discovered,the whole heading had become uniformly filled with a mixturecontaining 6 per cent.of methane. It has sometimes happened,also, that the slow ventilating current travelling through a roadleading from a goaf (or worked-out place) has been found to be aninflammable mixture, uniform in composition tliroughout itsextent.I n such cases the dangerous “ limit-mixtures” are such aswill allow of solf-propagation of flame throughout the wholemixture, whether ignition occurs a t the roof, floor, or centre of theroadway.The fire-damp of British mines consists of methane mixed withvarying proportions of nitrogen ; also, carbon dioxide, traces ofcarbon monoxide and ethylene may be present, and, occasionally,traces of ethahe have been detected.This paper records the results of determinations of the higher-and lower-limits of inflammability of mixtures of pure methanewith air, and shows how the compositions of the limit-mixtureFIG. 3.[ 7’0 ,face p . 2592FIG. 2.Prc:. 1. l ? I ( i . 4INFLAMMABILITY OF MIXTURES OF METHANE AND AIR. 2593differ, dependent on the manner in which ignition is effected.*These results are as follows :Methane, per cent.Lower limit. Higher limit.Central ignition in large globe .........5.6 14.8Vertical tube, closed at both ends :( a ) Ignition at bottom* ............ Not less than 5.40Horizontal tube, closed at both ends :Not more than 14.8'( b ) Ignition at top .................. 6.0 13-4I 5.4 (flame travels only( 5 . 6 (methane all burnt) j Ignition at one end ............ along top of tube) 14.3Coward aiid Brinsley obtained what appeared to be a self-propagating flame inone mixture containing, according to analysis, 5.3 per cent. of methane. They wereunable t o repeat the experiment.t The determinations made by IIauser (Zoc. cit.), using the Le Chntelier burette(downward propagation of flame), were : lower-limit 6-05 per cent ; higher-limit13-35 per cent.methane. Hwser obtained pure methane from alumininm carbide.The manner in which the flame travels in the different mixture'sis by no means the same, and an attempt has been made to indicatethe1 mere striking differences by diagrams. Fig. 1 represents theflam.e travelling upwards in a closed tube (6 cm. in diameter) coii-taining a 5.4 per cent. niethane-air mixture, aiid Fig. 2 the flametravelling horizontally in a like mixture. Figs. 3 and 4 illustratetwo stages in the progress of the flame downwards in a closed tubethrough a mixture containing 6.0 per cent. of methane.When an electric spark is passed at. the bottom of a closed vesselcontaining methane-air mixtures with 5.0, 5.1, 5.2, etc., per cent.of methane.flares of flame are produced which travel distancesincreasing with the percentage of methane, until with 5.4 per cent.of methane present the distance of travel reaches 2 metres in atube 2 metres long. It is possible that the flame in a 5.4 per cent.mixt'ure might travel upwards inoze than 2 metres; it might travelindefinitely, and, on the other hand, it might die out after adistance of 3 metres o r less. Since i t is obviously impossible t omake a crucial experiment' t o test this point, i t must suffice t orecord that the lower-limit mixture for upward propagation offlame contains not less than 5.4 per cent. of methane. The flamein mixtures containing 5.35 per cent.of methane, contained in aclosed glass tube 6 cm. in diameter, never exceeded a distance oftravel of 50 cm.; in 5.3 per cent. and 5-25 per cent. mixtures theflame travelled 40 cm. m d 30 cm. respectively.It will be seen in Fig. 2 that the flame travelling horizontally in* The influence of added nitrogen 011 the limits, as determined By centralignition in a large globe, is described in a subsequent paper2594 BURGESS AND WHEELER: THE LIMITS OFa 5.4 per cent. mixture occupies only the upper quarter or thirdof the containing vessel, and analysis of the mixture left in a tube6 cm. in diamet'er after the flame had travelled along i t showed itto contain 3-25 per cent. of methane. When a tube 10 cm. indiameter was used, 3.9 per cent. of methane remained in theproducts of combustion.Presumably, if a large room were filledwith such a mixture and a light applied a t some point near thefloor, a column of flame would travel upwards from the point ofignition to the roof and spread along the upper portion only ofthe room.It may not be generally known that when a slow current of aircontaining between 4 and 5 Fer cent. of methane passes over a smallflame, such as that of an oil lamp, the cap or aureole that ordin-arily forms round the lamp-flame may become detached and floatalong with the current. Similarly, if a slow current of air contain-ing 3 or 4 per cent. of coal gas is allowed to ascend a vertical tube,and a succession of electric spark3 passed a t the bottom, small capsof flame can be caused to pass from end t o end of the tube, onlya fraction of the mixture being burnt.Of a like nature aro such mixtures of hydrogen and air as allowI' balls " of flame to travel (perhaps indefinitely) upwards throughthem-with the convection-current-in the manner described byCoward and Brinsley.From the practical point of view such mixtures are not in them-selves dangerous, but they are potentially dangerous in that theycould convey flame to richer mixtures.From the scientific point of view it is or' interest €0 know thatsuch curious flames can be produced, but the doubt must alwaysremain whether actually '' indefinite " propagation of flame cantake place in the mixtures that exhibit them; and the fact thatchemical reaction proceeds in but a small portion of t'he wholemixture, renders it difficult to employ f o r comparative measure-ments the " criterion " of inflammability adopted by Coward andBrinsley.%* It should be noted that, making use of their criterion, Coward and Brinsleydecided upon 4'1 per cent.as the lower-limit percentage of hydrogen in air(3'8 per cent. of hydrogen remaining in the mixture after the flame had passed).Dixon and Crofts (this vol., p. 2047) have obtained the following figures for theignition-temperatures of various mixtures of hydrogen and oxygen :2H,+ 0, ............... 526'2H,+ 202 ............... 5112H,+ 80, ............... 4782H2+160, ............... 4722H,+3202 - ...............The last niixture, which contained 5.88 per cent.of hydrogen, could not beignited, although five expcrirnents were made in which the temperatures reacheINFLAMMABILITY OF MIXTURES OF METHANE AND AIR. 2595It may be remarked that if the object of their criterion ofiiiflammability is to specify the least quantity of inflammable gasin air that is capable of propagating flame, that object is notattained. For when a mixtare of methane and air containing5.0 per cent. of methane, enclosed in a 4-litre globe, is stronglyagitated by revolviqg a small fan therein, and an electric sparkis passed a t the' centre of the globe, flame travels rapidly throughoutthe mixture, all the methane being burnt. The lower-limit ofinflammability of " agitated " mixtures of methane and air couldtherefore be stated t o be 5-0 per cent., or possibly less with moreviolently agitated mixtures.The flame travelling downwards in a 6.0 per cent.mixture,depicted in Figs. 3 and 4, and the flame started centrally in a5.6 per cent. mixture contained in a large globe, both burn themethane completely. I n both cases the line of demarcation betweena mixture that will propagate flame and one that will not is sharplydefined.*For the latter reason, as well as for their convenience, thecriteria of inflammability for downward propagation, used byLe Chatelier and universally applied by French mining engineersf o r the1 measurement of fire-damp ; and for propagation throughouta globe, adopted by several investigators, would seem to commendthemselves f o r such comparative rneasurements as a study of thepropagation of flame in gaseous mixtures may demand.EXPERIMENTAL.The methane used was prepared from aluminium carbide, andwas purified from traces of acetylene by passing through ammmia-cal cuprous chloride, and from hydrogen by passing slowly over" oxidised '' palladium precipitate heatemd at 90°.It contained99.8 per cent. of nxhhane.The explosion-vessels were glass cylinders, sealed a t each end,were 500", 600", 700", lOOO", and 1700" respectively. Dixon and Crofts consideredthat the limit of inflammatdity had been passed in the last mixlure, but they notedthe fact that combuvtion occurred of part of the mixture.* The following deterrninations of the lower-limits, downward propagation,were made by Alr. A. Whitaker. With mixtures containing, according Lo aiiallysis,6.03, 6.02 and 6.01 per cent. of methane, flame was propagated throughout thelength of a closed tube 7 cni. in diameter and 160 cm. long. With 5-99, 5-98 and5.97 per cent. of methaiie the flame travelled 12 or 15 cm. only.A volume of mixture sufficient for two experiments was made containing 6.00per cent. of methane. After one experiment, i n which propagation of flame wascomplete, sufficient air was added to thc remainder of the mixture to reduce thepercentage of methane to 5'99; flame travelled downwards only 16 cm. in thismixture2596 BURGESS AND WHEELER: THE PROPAGATION OF FLAME TN6 cm. in diameter and 2 metres long. They were fitted withplatinum firing points a t one end and a t the' other with a three-way tap, through which the mixtures t o bO experimented withwere intsoduced after the cylinders had been exhausted of air. Themixt.ures were made over glycerol and water in graduated glassgas-holders, and were all analysed before use.Es I; YE A LS,CUMBERLAND

ISSN:0368-1645    

DOI:10.1039/CT9140502591

出版商:RSC    

年代:1914

数据来源: RSC

摘要:

2596 BURGESS AND WHEELER: THE PROPAGATION OF FLAME TNCCXLII.--The Pgdopayation of Flame in “Limit”Mixtures of Methane, Oxygen and Nitrogen.By MAURICE JOHN BURGESS and RICHAR~D VERNON WHEELER.IN a previous communication (T., 1911, 99, 2013) we argued that a“ lower-limit, ” mixture (and, similarly, a “ higher-limit ” mixture)is “one such that a given volume must, under the conditions of itscombustion, evolve just sufficient heat t o raise an equal volume t oits igriition-temperature.”According to this view, during the propagation of flame in any“limit ” mixture a balance is struck between heat generated bycombustion and heat employed in starting combustion, togetherwith heat “ lost ” by conduction and radiation.Theoretically, provided that the amount of energy imparted t othe system by the initial source of ignition-an electric spark, forexample-is small, so that no appreciable impetus t o the propaga-tion of flame occurs near the source of ignition, flame should travelthroughout a true limit mixture a t a uniform speed.Experiments,to be described a t a later date, establish the correctness of thissupposit ion.Further, it seems probable that the speed of travel of flame willbe the same in all limit mixtures that comprise the same constitu-ent gases. Experiments show this to be the case so far as horizontalpropagation in mixtures of methane, oxygen, and nitrogen isconcerned.Limit mixtures thus offer several advantages for the study of themanner of propagation of flame in gaseous mixtures.This paper contains the results of a series of determinations ofthe amounts of methane required to form higher- and lower-limitmixtures with various “ atmospheres ” ranging between air (20.9per cent.of oxygen) and a mixture of air and nitrogen containing13.45 per cent. of oxygen.** The results of preliminary experiments, obtained during the early months of1913, were communicated to the institution of Mining Engineers (Trans. Inst. Min‘‘ LIMI‘L’ ” MIXTURES OF METHANE, OXYGEN .lSD NLTROGEN. 2597The lower-limit mixtures contained a minimum of 5.6 per cent.of methane (when air was used) and a maximum of 6.45 per cent.(when the 13-45 per cent. oxygen “atmosphere” was employed).The minimum value for the higlier-limit mixtures was 6.7 per cent.of methane (with the 13.45 per cent.of oxygen “atmosphere ”) andthe maximum value 14.8 per cent. (with air).The compositions were thus determined of a number of limitmixtures containing widely different proportions of the same threegases-methane, oxygen, and nitrogen-from which calculationsof the heat bdances cauld be made with a reasonable expectationFIG. 1.12 13 14 15 16 17 18 190 1 ~ ‘ y p ~ in limit iuixtwes-per ccnt.that, although errors in calculating the specific heats of the gasesa t the ignition-temperatures of the mixtures might render theresults not strictly accurate, the relative values would be correct.The results obtained showing the percentages of methane thatform limit mixtures with the different ‘‘ atmospheres” can con-veniently bo given in the form of a diagram (Fig.1).I n this diagram percentages of methane are plotted againstEng., 1918, 46,1i, 125) by Mr. W. C. Blackett, a member of the Explosions inMiues Committee of the Home Office, a t whose request the work was cariied out.Since then accounts have appeared of similar researches by the United StatesBureau of Mines (Technical Paper, NO. 43, 1914) a i d by F. Le Prince Ringuet(Compt. rend., 1914, 158, 1999). Some deterniinations of the lower limits have alsobeen published by A. Parker (this vol., p. 1002).VOL. cv. 8 2598 BURGESS AND WHEELER: THE PROPAGATION OF FLAME INpercentages of oxygen in the limit mixtures. The different “atmo-spheres,” with the percentages of methane required iii each case toform higher- and lower-limit mixtures, are as follows:Atmosphere.Oxygen.I o g e n .20.90 79.10 (air)19-22 80.7818.30 81-7017-00 83.0015.82 84- 1814.86 85.1413.90 86-1013.45 86-5513.25 86.75Methane, per cent.L o w e r m l i m i t .5.60 14.82- 12.93- 11.916-80 10-555-83 8.966.15 8.366.35 7.266.50 6.70No mixture capable of propagating flameIt will be seen that as the oxygen-content of the atmosphereis reduced the higher- and lower-limits come closer together, untilwith 13.45 per cent. of oxygen only mixturw containing between6-50 and 6-70 per cent. of methane are capable of propagatingflame. A mixture of methane with an atmosphere containing13.25 per cent. of oxygen is incapable of propagating flame.Presumably the true ‘‘ extinctive ’’ atmosphere for methane-the atmosphere in which a jet of methane, however perfectlyaerated, would be just unable to burn-contains between 13.45 and13-25 per cent.of oxygen.*It may be noted that Haldane and Atkinson, who were thefirst to work on this subjech (Trans. Znst. .$fin. Eng., 1895, 8, 549),found that natural fire-damp could form an inflammable mixturewith oxygen and nitrogen when the oxygen present had beenreduced t o between 12 and 13 per cent. The higher- and lower-limit mixtures of pure methane with the 13-45 per cent. oxygenatmosphere, according to our experimemnts, contain 12.55 and 12.57per cent. of oxygen respectively.The general equation representing the heat balance during thespread of flame in a limit mixture is as follows:where cf, c’f represent the specific heats of the mixture ( M ) , and ofthe products of combustion (P) respectively, each a t the ignition-temperature ( T ) , t being the initial temperature of the mixture;q represents heat dissipated (by conduction and radiation), andz& heat evolved by t’he combustion of x parts of the combustiblegas.When methane is the combustible gas the calculations are com-plicated by the fact that combustion is incomplete. Appreciable* The extinctive atmosphere for methane is usually regarded as c ~ .~ t a i n i n g about17 per cent. of oxygen ; and the “residual” atmosphere-that in which a methaneflame has burnt to extinction-as containing about 15 per cent. of oxygen.( c ’ M + c f f P ) ( T - t ) + q = z & .. . . . (1(‘ LIMIT ” MIXTURES OF METHANE, OXYGEN AND NITROGEN. 2599quantities of carbon monoxide occur in the products of combustionof all the lower-limit mixtures, whilst with some of the higher-limit mixtures combustion is mainly to carbon monoxide, hydrogen,and stearn, and tho “ water-gas reaction ” proceeds as the productscool.Consequently, in order to calculate the heat balance jt isnecessary t o analyse samples of the products of combustion as soonas they are formed-before secondary reactions, which can playno part. in the propulsion of flame through the mixture, have takenplace.This was clone so far as practicable by withdrawing and coolingrapidly small samples of the “flame gases ” whilst the flames weretravelling through the mixtures (which were contained in largeglass globes), in the manner described in the experimental part ofthis paper.The analyses of these gases show a regular relationship betweenthe ratios O,,CH, in the original mixtures and the proportions ofmethane that burn completely to form carbon dioxide and steam.In the higher-limit mixtures the ratio 0,/CH4 varied from aminimum of 1-20 (in the mixture with air) to a maximum of 1.87(in the mixture with the 13.45 per cent. oxygen “atmosphere”).The proportion of the methane burned in the former mixture t ocarbon dioxide and steam was 32.2 per cent.; in the latter mixtureit was 83 per cent.The results have been summarised as follows:Oxygen-contentatmosphere.20.90 (air)19-2218.3017.0015.8214.8613-9013.45of Ratio OJCH, inhigher-limit mixture.1.201.291-351.441.601-621.771-87Proportions of methaneburned to carbondioxide and steam.32.237.842.649-059.064.577.483.0As the proportion of oxygen t o methane is increased, more andmore of the latter is completely burned.With a ratio 02/CH4 = 1.50half the methane burns to carbon dioxide and half ta carbonmonoxide; whilst when the oxygen present is less than one anda-half times the methane present the main reaction is representedby the equation:CH4 + 0 2 = CO + H, + HZO.For comparison with these results those obtained by Bone andDrugman with mixtures of methane and oxygen in equal propor-tions may be quoted (T., 1906, 89, 676).The percentage composi-tion of the gaseous products of combustion (no carbon was8 ~ 2600 BURGESS AND WHEELER: THE PROPAGATION OF F1,AME INdeposited) averaged: W2, 6 . 3 ; CO, 41*9; H,, 50.8; CH,, 1.0.Commenting OD these results, Bone and Drugman say: “It hasbeen shown that, below the ignition-point, methane burns, forminga t an early stage steam and formaldehyde. The process mayprobably be best expressed as follows:CH4 --+ CH,*OH -+ CH,(OH), + CH20 + H,O, etc.‘ I A t high temperatures the formaldehyde would certainly decom-pose into carbonic oxide and hydrogen, so that in explosivecombustion we should obtain :CH,O+7 CH, + 0, = CO + H2 + H20.“The 6 par cent. of carbon dioxide formed in our experimentswould obviously arise by the secondary interaction of steam andcarbonic oxide in the flame.”A s a general conclusion from our results, we hold the opinionthat the essential reaction in the propagation of flame in theselimit mixtures is that responsible for the formation of carbonmonoxide, hydrogen, and steam in equal volumes.The heat cvolved by this reaction is probably almost equallydivided between the products of combustion of one “layer” ofmixture and the adjoining unburnt “ layer ” ; it is, however, insuffi-cient to raise the unburnt layer to its ignition-temperature.Follow-ing rapidly upon this reaction, some of the carbon monoxide andhydrogen is burned, the proportion depending upon the oxygen-concentration. Tho additional heat added t o the system in thislatter manner enables the nearest unburnt layer to attain itsignition-temperature.Finally, as the burnt gases cool, the water-gas reaction comesinto play, as is shown by comparison of the analyses of the “flamegases ” and “ final gases” for the same mixture (compare also(‘ The Water--Gas Equilibrium in Hydrocarbon Flames,” by G.W.Andrew, this vol., p. 444).Assuming this to be the correct interpretation of the sequence ofevents, calculation of the heat balance of each mixture can bemade, using the data supplied by the analyses of the flame gases.Calculation having been made of the percentages by weightof the constituent gases of the mixture composed of equal volumesof burnt and unburnt gases, equation (1) can be put in the form:(co& 4- CCH~B 4- CN~C 4- Cc0,U f CcoE f CH%T+ Q20G)(T - 1 ) f Q =xQ + z’Q’,co2.CCH~, etc., being the specific heats of the respective gases a tthe tenperature T - t , and A , B, etc., the percentages by weight ofthose gases. Of the methane burned, x grams form carbon dioxid“ LIMIT ’’ MIXTURES OF METHANE, OXYGEN AND NITROGEN. 2601and steam, the heat evolved by the reaction being Q calories pergram; aild $1 grams form carbon monoxide, hydrogen, and steam,the heat evolved by the reaction being Qf calories per gram.*Some doubt attaches to the value which should be assigned ineach case to T, the ignitiontemperature of the mixture. Tablesof the “ignition-temperatures” of various gases do not, in themajority of cases, afford information as to the percentage composi-tion of the mixture formed by the combustible gas with air (oroxygen) when ignition occurs.Thus, the experiments of Dixon andCoward (T., 1909, 95, 514), in which a heated jet of the combust-ible gas was aIIowed to flow into a heated atmosphere of air oroxygen, only determined for each gas the ignition-temperature ofthe mixture having (presumably) the lowest ignition-temperature,without showing the composition of that mixture.I n a recent paper by Dixon and Crofts (this vol., p. 2036) therelative ignition-temperatures of different mixtures of hydrogenand oxygen, determined by the method of adiabatic conzpressionsuggested by Nernst, are given, and it appears that increasedoxygen-concentration is accompanied by decreased temperature ofignition.A similar conclusion for methane-air mixtures may bedrawn from the experiments of Taffanel and Le Floch (Compt.rend., 1913, 157, 469); so long as the ratio 02/CH4 was greateror not much less than 2.0, the ignition-temperatures of the mixtureswere the same ; a continued increase in the methane-concentration,however, was accompanied by a regular increase in the ignition-temperatures of the mixtures.Using this relationship between oxygen-concentration and igni-tion-temperature, established by Taffanel and Le Floch, we havecalculated the ignition-temperatures of our mixtures, taking Dixonand Coward’s lowest figure as being probably most nearly correctfor mixtures having ratios 0,/CH4=2-0 or m0re.t The tempera-tures range between 650° for such mixtures and 715O for the* The values employed in our calculations are: for the reaction CH,+20,=C0,+2H20, &=11,910 calories per gram ; for thc reactionQ= 3240 calories per gram.chosen the following determinations :CH,+O,=CO+H,+ H,O,For the specific hpatv (at constant volnme) we haveOxygen ....................................0.1548 0.000023tMethane ................................. 0.4501 0-000016tNitrogen ................................. 0.1677 0-000016tCarbon dioxide ........................ 0.1531 0.000059tCarbon monoxide ..................... 0.1730 0.00001 6tHydrogen ................................. 2.4020 0.000016tSteam .................................... 0.3300 0.000120tt Taffanel and Le Floch, in their determinations, did not adequately allow, a9 didDixon and Coward, for the influence of heated surfaces2602 BURGESS AND WHEELER: THE PROPAGATION OF FLAME INmixture having a ratdo O,/CH,= 1-20 (the higher-limit mixturewith air).The results of the calculations are shown in Fig.2, where Q, theheat evolve'd, is plotted f o r each limit mixture against q, the heatunaccounted for or "lost." It will be seen that the two are practi-cally proportional, the heat unaccounted for averaging f o r eachmixture 35 per cent. of the total evolved.This heat-loss, the magnitude of which is no doubt due to thefact that the accumulation of sufficient energy for the propagationof flame is a prolonged process-$he combustion of methane takingplace " by stages," * is necessarily made up of loss by (I) conduc-tion and convection, and (2) radiation.The number of calories t'ransmitted by the flame to any givendistant layer of unburnt gas by conduction and convection can beF I G .2."18 19 20 21 2's' 23 24Q= Lniye calories.regarded as approximately proportional to the difference in tem-perature between the two, and a curve representing such trans-mission of heat by flames of different temperatures would be, asiiearly asgossible, a straight line.As regards heat transmitted by flames as radiant energy-which,be it noted, has been found in the case of non-luminous coal gasflames, 30 mm. in diameter, may amount to as much as 15 or20 per cent. of the whole heat of combustion I--the effect of tem-perature is more difficult to estimate. Callendar suggests thatPlanck's equation for a single wave-length may be assumed, and,for a Bunson flame of mean wave-length 3 .5 ~ ~ gives the followingtable of approximate values for the variation in intensity with* The well-known " lag " in the ignitioii of methane is also explicable from thisI- Third Report, Gaseous Explosions Committee, British Associatioil, Appendix A.cause (compare T., 1911, 99, 2020)‘- .LIMIT ” MIXTLJIIEX OE’ METHANE, OXYGEN AND NITROGEN. 2603temperature, for comparison with the fourth-power law of Stefanfor the radiatdon of a black body:Absolute temperature ... 1000” 1500’ 2000’ 2500’ 3000’Radiation, Planck. ......... 0.016 0.059 0.142 0.233 0.331Radiation, Stefan.......... 0.009‘ 0-045 0.142 0.347 0.721Commenting on this table, Callendar says: “The rate of varia-tion, according to Planck’s formula for a single wave-length, ismuch slower than r,he fourth-power law, and tends in the limit tobe directly proportional to the absolute temperature a t high tem-peratures. The actual rate of variation should lie between theselimits, but nearer to Planck, unless carbon begins t o separate inrich mixtures at high temperatures.” *As already noted, q, the’ “loss” of heat from our mixtures (innone of which did carbon separate), is practically directly propor-tional t o &, the total heat evolved.EXPERIMENTAL.The different mixtures of oxygen and nitrogen were made inlarge glass gas-holders holding sufficient f o r a dozen or moreexperiments, and thO limit mixtures with methane prepared fromthem in smaller gas-holders over glycerol and water.The method of determining the limits, and the apparatusemployed, were similar to those described in our previous paper(Zoc.cit., pp. 2020-2024). The methane used was prepared fromaluminium carbide, and was purified from traces of acetylene bypassing through ammoniacal cuprous chloride, and from hydrogenby passing slowly over ‘( oxidised ” palladium precipitate heatedat 90°.Each mixture was analysed, the methane being determined byexplosion (with electrolytic gas or excess of air and oxygen addedas the case might require), and the oxygen by absorption bystrongly alkaline pyrogallol.A large num-ber of experiments with each atmosphere were madebefore the limits were fixed as closely as was desired.Correspond-ing mixtures were then carefully prepared and inflamed in aspecial form of explosion-vessel designed for securing a sample ofthe ‘( flame gases ” whilst the flame was travelling (Fig. 3, p. 2592).This explosion-vessel was a Zi-litre globe, with glasscoveredelectrodes reaching t o the centre. Through the side of this globewere fused, in the positions shown in the photograph, two finecapillary tubes, either of which could make connexion, through athree-way tap, with a small bulb filled with mercury t o within4.5 C.C. of its capacity. The space above the mercury in this small* Third Report, Gaseous Explosions Comniittee, British Association, Appendix A.It contained 99.7 per cent.of methanePer cent. by volume.Osygen- Lnalysis ofcontent Description limit mixture. Analysis of flame gases.of of limit 7- / \ /-20.90 (air) Higher 17.80 14.82 67.38 4.80 nil 10.10 10.50 0.85 73.75 4.9919.32 ,, 16.74 12.93 70.33 5.00 nil 8.19 8-19 0.72 77.91 5.3218.30 ,, 16.12 11.91 71.97 5.37 nil 7.23 7.26 0.82 79.32 5.5517-00 ?, 15-22 10.55 74.23 5-55 nil 5.78 5.75 0.38 82.54 5.6815.82 ,, 14.40 8.96 76.64 6.03 nil 4.19 2.93 0.25 86.62 6.4314.86 ’,, 13.59 8.36 78.05 6.27 nil 3.45 2.56 0.34 87.38 6.3913.90 ,, 12.88 7.26 79.86 6.41 nil 1.87 1.20 0.37 90.15 6-5213.45 ,, 12.55 6-70 80.75 6.62 nil 1.36 nil 0.55 91.32 6.9213-45 Lower 12.57 6.50 80.93 6.82 nil 1.31 0.35 0.35 91.17 6.9313.90 ,, 13.00 6.35 80.65 6.57 0.56 0.60 0.45 nil 91.82 7.2714.86 ,, 13-95 6-15 79.90 6.46 1.54 0.48 0.18 nil 91.34 7.0015.82 ,, 14.89 5.83 79.28 6.23 3.43 0.32 0.10 nil 89-92 6-6020.90 (air) ,, 19-73 5-60 74.67 6.25 9.65 0.07 nil nil 84.03 6.30atmosphere.mixture. 0,. CH,. N,. CO,. 0,. CO. H,. CH,. N?. CO,“ LIMIT’’ MIXTURES OF METHANE, OXYGEK AND NITROGEN. 2605bulb was thoroughly exhausted of air, and served, when the three-way tap was rapidly opened, to capture a sample of the gases a teither of the two points where the capillary tubes ended withinthe explosion-vessel. When the whole apparatus was inverted thissample could be withdrawn, by means of a mercury pump, throughthe tap shown a t the bottom of the photograph.I n all the limit’ mixtures the manner in which the flame travelledwas the same.So soon as the igniting spark had been passed aflame shot up to the top of the vessel, bent over, and, after thusfilling the whole of the to2 quarter of the globe, travelled down-wards t o the bottom as a uniform layer of light blue colour.+ Thislayer had an apparent thickness of between 13 and 2 inches, andtravelled sufficiently slowly to enable the tap leading t o thesamplingvessel to be manipulated a t the right moment.The moment chosen for all the samples of which analyses aregiven in this paper was when the layer of flame had passed half-way past the end of the upper capillary tube, as indicated inFig. 3 by the shading added to the photograph, which gives a veryfair idea of the appearance1 of the flame when observed throughthe side of the globe a t the moment of sampling.The gases were driven into the samplingvessel under pressure ofbetween 2 and 3 atmospheres, so that, although the space in thatvessel unoccupied by mercury was under 5 c.c., between 10 and15 C.C. of gases were obtained f o r analysis.Samples of the products of combustion remaining in the explo-sion-vessel were withdrawn for analysis after sufficient time hadbeen allowed for complete mixture.Results of 3zperiments.-The compositions of the limit mixtures,and the analyses of the “flame gases” and final gases” are givenon p. 2604.A correction has been introduced in the analyses of flame gasesfor the unburned mixture contained in the capillary-tube leadingto the sampling-vessel.The last two columns in the table record the calculated values ofQ and p plotted in Fig. 2.These results have already been discussed in the theoreticalportion of this paper. An additional point that should be notedis the preferential burning of hydrogen over carbon monoxide inall the mixtures that contain a ratio O,/CH, greater than 1.5.ESRMEALS,CUMBERLAED.* In some of the higher-limit mixtures the flame had a slightly reddish tinge

ISSN:0368-1645    

DOI:10.1039/CT9140502596

出版商:RSC    

年代:1914

数据来源: RSC

摘要:

2606 WHEELER: THE PROPAGATION OF FLAME INCCXLII1.-The Propagation of Flame in Mixtui-es ofBy RICHARD VERNON WHEELER.IN the course of their well-known remarches on the combustion ofexplosive gaseous mixtures, Mallard and Le Chatelier (Ann. desMines, 1883, [viii], 4, 274) studied the propagation of flame inmixtures of methane and air contained in horizontal tubes. So faras such mixtures are concerned, the general cbnclusions drawn bythem regarding the manner in which flame is propagated were asfollows.When the mixture contained in a horizontal tube closed a t oneend and open a t the other is ignited a t the open end, the flametravels for a short distance a t a uniform speed. This “uniformmovement ” is followed by a “vibratory movement,” in the courseof which the flame travels backwards and forwards in an irregularmanner, the mean speed from point t o point along the tube beingusually greater than that of the “uniform movement.’’ Thesevibrations usually continue t o the end of the tube, but sometimesduring a particularly violent, vibration the flame may be extin-guished, owing t o the rnixing of burnt gases with the unburntmixture.When the mixture is ignited a t the closed end of the tube theflame travels, in shori; tubes at all events, with increasing speedtowards the open end.I n the course of investigations on mine explosions, carried out,in the first instance, for the Mining Association of Great Britain,and, latterly, a t the Home Office Experimental Station, the neces-sity arose for repeating Mallard and Le Chatelier’s experimentsregarding mixtures of methane and air.The present paper deals with the ‘‘ uniform movement,” the speedof which is the normal speed of propagation of flame by conductionof heat from layer to layer of the mixture, and is constant for agiven mixture a t a given temperature and pressure.Mallard and Le Chatelier made a complete.study of how far thediameter, length, and material of the tubes influenced the speedand duration of the uniform movement in many gaseous mixtures,with the object of determining the limiting dimensions requisitet o ensure that the true speed-the speed that would be obtainedin a mixture of indefinite extent-should be determined.Giventhe right dimensions of tubes, the material of which they weremade did not appreciably affect the speeds.Repetition of MallardMethane and Ah*. The ‘‘ i7r~ifoor.m Movement.MlXTURES OF METHANE AND AIR. 2607and Le Chatelier’s experiments regarding these experimental condi-tions has confirmed their results.The diameter of tube necessary t o avoid cooling by the walls,and consequent retardation of the flame, was found to be greaterthe slower the speed of the flame. For the most slowly movingflames in mixtures of methane and air it tube of a t least 5 cm.diameter is necessary. The speed of travel of flame in a tube 9 cm.in diameter is slightly greater than in a tube 5 cm. in diameter.The duration of the uniform movement, which varies with eachmixture, increases with the diameter and length of the tube up t oa certain maximum, after which increase in length makes no appre-ciable difference.I n a tube 5 cm. in diameter and 6 metres longthe uniform movement in all mixtures of methane and air extendsover a dist.ance of about 150 cm., whereas in a tube of the samediameter and 2 metres long the distance travelled by the flame a ta uniform speed may be less than 50 cm.For their experiments Mallard and Le Chatelier used tubes5 cm. in diameter and 1 metre long, and measured the speed oftravel of flame over tho first 50 cm. The length of the tube wasinsufficient to ensure that the measurements of the speed of theflame would not include part of the “vibratory movement,” a factwhich they themselves realised (Zoc. cit., p.317). Their measure-ments for the same mixture show, in consequence, rather widevariations. Their experiments were further vitiated by the factthat the methane used was prepared from sodium acetate (“i1exhalait une forte odeur d’acetone ”). Such methane ” maycontain as much as 10 per cent. of nitrogen, 10 per cent. ofunsaturated hydrocarbons, and 2 or 3 per cent. of hydrogen.*The conclusions drawn by Mallard and Le Chatelier were:(1) The speed of the uniform movement increases regularly withthe percentage of methane up to a certain maximum, after whichi t decreases regularly. The curve obtained on plotting speeds asordinates and percentages of methane as abscissze is thus repre-sented by two straight lines meeting a t a point. Their curve(from Plate VIII of their paper) is reproduced in Fig.1.(2) The maximum speed is obtained, not with that mixturecontaining the quantity of methane required for complete com-bustion, namely, 9.4 per cent., but with a mixture containingabout 12 per cent. of methane. Le Chatelier (“Leqons sur lecarbone,” Paris, 1908) explains this result by assuming that thespeed of propagation of flame during the uniform movementdepends, not only on the temperature of combustion of the mixture,but on its thermal conductivity, which is greater the greater the* Compare Hauser, “ Leqons sur le grison,” Madrid, 19082608 WHEELER: THE PROPAGATION OF FLAME INproportion of methane present. The thermal conductivities of airand of methane are 5.22 x 10-5 and 6-47 x 10-5 respectively.Fresh determinations, made in the manner described in theexperimental portion of this paper, do not bear out Mallard andLe Chatelier’s results.The form of curve obtained on plottingspeeds as ordinates and percentages of methane as abscisse isshown in Fig. 1.It will be seen that there is practically no difference between thespeeds attaineld in mixtures containing from 9-45 t o 10.55 percent. of methane,* such differences as there are being probablywithin the limits of experimental error.Near the lower- and higher-limits of inflammability, which, forhorizontal propagation, are 5.4 and 14.3 per cent. respectively, theFIG. 1.6 5’4 6 7 8 9 10 11 12 13 1414‘” 15 16 17AIcthnne in fit-ednnzp-air mixture, per cent.curve flattens, more noticeably towards the higher limit, andbecomes, ultimately, nearly horizontal.It will be understood,therefore, that a prolongation of either “limb” of the curve 60as t o cut the zero velocity ordinate, as done by Nallard andLe Chatelier to determine the theoretical limits of inflammability,is not justifiable.Vibrations were not developed by the] flames in all the mixtures.I n those containing more than 12.5 o r less than 5.8 per cent. ofmethane the flame usually travelled a t a uniform or slightly decreas-* This conclusion is confirmed by another series of experiments in whichdifferent mixtures of methane aud air were ignited a t the centre of a large sphericalexplosion vessel. The tirrie that elapsed between the moment of ignition and thefirst indication of pressure on the sides of the vessel was less the higher the per-centage of methane in the mixture up to 9.5 per cent.methane, after which itremained practically constant up to 11 per centMIXTURES OF METHANE AND AIR. 2609iiig speed throughout the length of the tube, although sometimesslight vibrations were noticeable in all but the " limit-mixtures."I n these latter the speed of travel of flame was quite uniformthroughout,, and was the same for both the higher- and lower-limitmixtures.As noted in a previous paper (this vol., p. 2593), the flameF I G . 2 .travelling horizontally in a 5.4 per cent. methane-air mixture,contaiued in a tube 5 em. in diameter, occupies only the upperpart of the tube. The flames in the other mixtures of methane andair, including the higher-limit mixture, completely filled the cross-section of the tube, the front of the flame (during the uniformmovement) being shaped as shown in Fig. 2.The faster the speedof the flame the blunter was its front.EXPERIMENTAL.The arrangement of glass tubes is shown in Fig. 3. Three lengthsof t'ube of 5 cm. internal diameter, each 2 metres long, were joinedtogether by broad pieces of stout rubber tubing, and supportedhorizontally in a straight line. Each end of the complete lengt2610 WHEELER: THE PROPAGATION OF FLAME I Nof 6 metres was flanged and ground t o receive flanged end-pieces,which were held in position by metal clips. Each end-piece wasfitted with a wide-bore three-way tap.Glass-covered platinum elec-trodes reaching to the centre of the tube, leaving a spark-gap of3 mm., were fused 4 cm. from one end.Another tube, similarly arranged, but of 9 cm. internaldiameter, was used for a separate series of experiments.“ Screen-wires ” of copper 0.025 mm. in diameter were threadedvertically across the tube through fine holes pierced through thewalls a t certain points, the holes being afterwards covered byadhesive plaster. In order t o avoid including in the measurementsof the speed of the flame any impetus that might be given by theigniting spark, the first screen-wire was fixed 40 em. from the pointof ignitlon. OGher screen-wires were fixed 50, 100, 200, 300, and400 cm. respectively from the first.The method of recording the time of passage of flame along thetube was erectrical.Each screen-wire carried a small electriccurrent, the interruption of this current when the flame meltedthe wires being recorded by the movement of an electro-magnet.It was important to avoid error due to latency or “timelag” ofindividual electromagnets. An instrument, which can be termedan automatic commutator, was therefore designed to enable eachsuccessive break in circuit to be recorded by the same electromagnet.This instrument is operated in the following manner:One terminal of the battery supplying the electric current isconnected to the brush, -4, of the commutator (Fig. 3), and a leadfrom the other terminal of the battery conducts the current t o theelectromagnet of the chronograph, so that its armature is attracted.The current tEen passes by a lead to the electromagnet on thecommutator, and that armatare is also attracted; the lead carryingthe current then goes t o one terminal of the scre’en-wirea on theexplosion-tube one after the other; the other terminal of eachscreen-wire is connected to the corresponding stud on the commu-tator by separate leads.Supposing the brush, A , to ue resting on No.1 stud (the positionthat it occupies a t the beginning of an experiment), the current isthen flowing through the chronograph electromagnet, the commu-tator electromagnet, and No. 1 screen-wire; then through thebrush, A , back t o the battery. Suppose now that the flame passesalong the tube’ and melts screen-wire No.1; the chronographelectromagnet rolease; its armature, and the pen it carries makesa mark on the moving surface; a t the same time the armature, B,of the commutator electromagnet is released, and the anchor-escapement, C, attached to the armature, is moved. This allows thMIXTURES OF METHANE AND AIR. 2611coiled spring, D, to pull the scapewheel, 3, round by the cord, F ,which is wound on a drum attached to the axis of the scape-wheel.The brush, A, then moves on 50 stud No. 2, and the current atonce begins to flow through screen-wire No. 2; the chronographelectromagnet and the commutst.or electromagnet, and the arma-tures of both these are again attracted; the pen on the chrono-graph is moved back to its former position, as also are the armature,13, and the escapement, C, whilst the brush, A , moves a littlefurther on to stud No.2. When the flame reaches No. 2 screen-wire the same cycle is repeated and so on for as many screens asmay be required, all the interruptions of circuit being recorded bythe one pen on the chronograph.*The chronograph used was the laboratory chronograph of theCambridge Scientific Instrument Company, the speed of travel ofthe moving surface (a spool of Morse paper) being recorded by a$-second contact-clock.Xethod of Ccnducting a2z Experiment.-The mixtures ofmethane and air were made in a 140-litre gas-holder over waterrendered slightly alkaline by potassium hydroxide. A rapidcurrent of the mixture was passed through the explosion-tube untilthe gases entering and leaving had the same composition, a8 shownby explosion-analyses of samples taken through the three-way taps.A volume of mixture equal to about six times the volume of thetube was found to be ample for sweeping out all the air containedin the tube.All electrical connexions through the screen-wires and chrono-graph having been established, the left-hand end-piece of theexplosion-tube was removed (by sliding it downwards) and themixture ignited a t the now open end by passing an induction-coilspark.The methane used was a particularly pure supply of fire-dampfrom a " blower" a t a colliery in South Wales, whence it wasobtained compressed in cylinders.Analysis, after removal of0.8 per cent. of carbon dioxide, showed it t o contain 97.4 per cent.of methane, 2.3 per cent.of nitrogen, and 0.3 per cent. of otherimpurities (carbon monoxide and ethylene). It contained nohydrogen or ethane.* A somewhat detailed description of this device has been given in the belief thatit may prove of value to other workers. The author has fvund it adequate formeasuring the speed of the rapidly inoviiig fl'rmes of coal dust explosioiis and coal-gas and air explosions in large galleries. Its effectiveness depends essentially onthe rapidity with which the brush of the commutator can be made to move fromone stud t o the next ; by snitable proportioiling and adjustment of the movingparts and regulation of the electric current passing through the magnets, the timetaken for the brush to move from stud to stud can be niade as little as &th second261 2 WHEELER : THE PROPAGATION OF FLAME. ETC ..Results of E'xperzments.-The rssulb of all the determinationsmade of the speed of the uniform movement in different mixturesare given in the table that follows .As a general rule, the uniformmovement extended for a distance of 150 cm . from the point ofignition. so that from each experiment wit'h a particular mixturetwo determinations of the speed were obtained (between No . 1 andNo . 2. and between No . 2 and No . 3 screen-wire respectively) .Some of the more rapidly-moving flames. in mixtures containingbetween 9.5 and 11.0 per cent . of methane. began to vibrate justbefore reaching tile third screen-wire; in such cases only the speedbetween screen-wires Nos . 1 and 2 was taken as being that of theuniform movement .Methane in fire-damp-airmixture. per cent .Speed of " uniform movement " offlame. ern . per second .5-40 ........................ 36.5, 36.0, 35.5, 35.5, 35.5, 35.5, 36.0,5.60 ........................ 37.0, 37.0.5-85 ........................ 40. 40.5, 40.5, 40.5.6.25 ........................ 46. 46. 45.5, 45. 45.5, 45. 45.5.6.80 ........................ 56. 55. 55. 55 .36.0, 35.5 .6.75 ........................ 54. 54 .7.10 ........................ 61. 59. 61. 59 .7-70 ........................ 77. 77. 75. 75 .9.10 ........................ 105. 104. 106. 104 .9.20 ........................ 108. 109 .9.45 ........................ 110.110. 110. 110 .9.60 ........................ 111. 111 .9.80 ........................ 111. 112 .8-36 ........................ 91. 90 .8.80 ........................ 100. 100. 99. 100 .10.00 ........................10.60 ........................ 109. 109. 109 .10.90 ........................ 102. 102. 101 .11-00 ........................ 100. 98. 99. 99 .11.20 ........................ 93. 92 .11.50 ........................ 84. 84. 83. 83. 85. 84 .12.10 ........................ 62.5, 62 .12.50 ........................ 50. 50. 49 .12.65 ........................ 49. 47. 48. 46 .13.00 ........................ 42.5, 42. 42. 42 .13.05 ........................ 41. 40.5.13.30 ........................ 39. 38. 39. 38. 38. 38. 38 .13-80 ........................37. 36.5.14.30 ........................ 36.0, 35.5, 35.5.112. 110. 112. 113. 112. 110. 109. 113 .For Lne determinations of the speed of travel of flame in thehigher-limit mixture pure methane was used. since the 2.3 per cent .of nitrogen contained in the fire-damp slightly affected the higherlimit. whereas it had no appreciable effect on the speed of travelof flame in the other mixtures (compare this vol., p . 2596) .A similar series of clet'erminations was made. using an explosion-tube of 9 cm . internal diameter . The speeds were from 5 t o 10 cm .per second greater than those of corresponding mixtures in thetube 5 cm . in diameter . The shapes of the curves connecting speedVOLATILE OIL FROM THE LEAVES OF UAROS&IA VENUSTA. 2613with percentages of methane, and the limits of inflammability, weretlie same in both series of experiments.The' propagation of flame in mixtures of methane and air, andin mixtures t o which nitrogen has been added, has been furtherstudied. Ail account of the work will be communicated later t othe Society.Adde?idum.Since this paper was prepared an account has appeared of experi-ments on the samel subject by A. Parker and A. V. Rhead (thisvol., p. 2150). It is surprising to find that these aut'hors are appa-rently unacquainted with Mallard and Le Chatelier's completeresearches dealing with the " uniform " and " vibratory " move-ments during the propagatior of flame in gaseous mixtures con-tained in glass tubes, as outlined in the present paper. Theirresults are interesting in that they emphasise the necessity, pointedout by Mallard m d IJe Chatelier, of employing tubes of amplediameter when conducting experiments of this nature; the tubesthey used were of too sniall a diameter t o enable them t o determineeither the true character of the speed-percentage curve or the limitsof inflammability

ISSN:0368-1645    

DOI:10.1039/CT9140502606

出版商:RSC    

年代:1914

数据来源: RSC

摘要:

VOLATILE OIL FROM THE LEAVES OF UAROS&IA VENUSTA. 2613CCXL1V.- Volcctile Oil from the Leaves o j ’ Barosmavcnusta.By ERNEST GOULDING and 0 s WALD DIGBY ROBERTS.THE genus Barosmu, of which about thirty species exist in SouthAfrica, derives its chief iniportance from the fact that certainspecies yield the so-called Buchu leaves, which are employed inmedicine as mild disinfect,ants of the urinary tract. The physio-logical activity of the leaves is principally due to the volatile oilwhich they contain. The source of Buchu leaves of the BritishPharmocopoeia, or short Buchu,” is Barosma betzdina, Bartl. andWendl., but the leaves of 13. creizulata, Hook. and B. s e w a t i f o h ,Willd., are also met with in commerce under the name of “longBuchu.”Another species of Barosma, 13.uenusta, Eckl. and Zeyh., occursin considerable quantities in the Uitenhage District of t’he CapeProvince. Information was desired in South Africa as to thepossible value of the leaves of this plant in comparison with BuchuVOL. cv. 8 2614 GOULDING AND ROBERTS: VOLATILE OIL FROM THEleaves, and an examination of the material was therefore under-taken a t the Imperial Institute.The most characteristic constituent of the oil of Barosma betalinais diosphenol, which is present in quantities of 20-30 per cent.;the oils of B, menulata and B. serratifolia, however, contain only avery small proportion of this substance. The' results of the presentinvestigation show that the oil of B. venusta differs very consider-ably in odour and composition from that of Buchu leaves, andthat it does not contain any diosphenol.I n 1911 a sample of the leaves of Barosma venusta was receiveda t the Imperial Institute from the Cape Province, South Africa.On distillation in a current of steam it yielded 2.7 per cent.of avolatile oil, which was of a lemon-yellow colour and pleasant odour,and had D15 0.877 and a: 1°4' in a 100-mm. tube.A larger consignmenb of the leaves, forwarded in 1913, fur-nished 2.0 per cent. of volatile oil with the following constants:DI5 ............................................................ 0.865a y in 100 mm. tube ....................................... +0°47'Acid value ................................................... 6.6Ester value ................................................ 6.2(Corresponding with 2.2 per cent.of esters, calculated88 C,,H,,*OAc.)Ester value after acetylation ........................ 55(Corresponding with 15.7 per cent. of total alcohols,or 14-3 per cent. of free alcohols and 2.2 per cent.of esters.)Fractional Distillation of the Oil.On distilling the oil under atmospheric pressure the followingfractions were obtained, but some decomposition occurred :Fraction. Per cent. Boiling point. DI5. aD in 100 mm. tubeI. 44 163-190" 0.8100 inactive.11. 17 190-205 0.8932 inactive.111. 28 205-230 0.9531 + O"30'IV. 9 230-246 0.9610 liquid too dsrn-coloured to admitof this determina-tion.- - - Residue 2Isolation and Identification of Myrcene.When a portion of the oil was distilled under 60 rnm.pressure,about 48 per cent. collected between 83O and 88O. This fraction,after being treated repeatedly with sodium and redistilled, hadD15 0.8060, and was optically inactive; it distilled a t 163-173Ounder atmospheric pressure, but suffered partial decompositionLEAVES OF BAROSMA VENUSTA. 2615This hydrocarbon exhibited the properties characteristic ofmyrce,ne, for which the following constants have been recorded :Power and Kleber .................. D15 0.8023 b. p. 167".Chapman .............................. DI5 0.8046 b. p. 166-168".Enklaar4 ................................. D15 0.8013 b. p. 166-168".Phnrm. ItundscR., 1895, 13, 61.T., 1903, 83, 507.Semmler - b. p. 171-172'. ..............................Semmler and Mayer5 Dm 0.7937 - ...............Ber., 1901, a, 3216.Diss., Utrecht, 1906.Ber., 1911, 44, 2010.The terpene showed a great tendency to resinify, and readilycombined with four atoms of bromine.On reduction with sodiumand alcohol it was converted into a compound having D15 0.7860,a value which agrees well with those recorded for dihydromyrcene,namely, 0.7802 and 0.7852, by Semmler (Zoc. cit.) and Enklaar(Zoc. cit.) respectively. This reduction product furnished a tetra-bromide, melting a t 9l0, which crystallised from methyl alcohol inhard, white needles. The melting point of dihydromyrcene tetra-bromide has been given as 87O by Semm'ler and Mayer (Zoc. cit.)and 8 8 O by Enklaar (Zoc. cit.). By the action of a mixture ofglacial acetic acid and sulphuric acid on the original terpene, anacetate was obtained which resembled linalyl acetate in odour, and,on hydrolysis, yielded an alcohol.This alcohol, when oxidised withchramic acid, did not furnish citral, but the odour of the productsuggested the presence of some other aldehyde. These observationsaccord with those of Barbier (Compt. rend., 1901, 132, 1048) onthe oxidation of myrcenol. The existence of myrcene in the oil istherefore established.Aldehydes : Identification of Anisaldehyde.A portion of the oil was shaken with solution of sodium hydrogensulphite. After the aqueous liquid had been separated and washedwith ether, it, was readered alkaline by the addition of sodiumhydroxide, and extracted by repeated agitation with ether.Theethereal solution was dried with anhydrous sodium sulphate, andthe ether was removed by distillation, The residue, amounting t oabout 0.5 per cent. of the original oil, appeared from its taste andodour to consist chiefly of anisaldehyde, and, on oxidation withpotassium Fermanganate, was readily converted into anisic acid,which after recrystallisation melted a t 183-184O (anisic acid hasm. p. 184O).8 H 2616 VOLATILE OIL FROM THE LEAVES OF RAROSMA VENUSTA.dlcoliols : Itrdicntioti of the Presetzce of Liriulool.The fraction boiling atd 190-205° under atmospheric pressureconsisted largely of alcohols, and had a sweet odour resemblingthat of linalool; on oxidation i t yielded citral, which was charac-terised by its odour and by the preparation of a-citryl-P-naphtha-cinchoniiiic acid, melting a t 1 9 9 O .It is therefore proba,ble that thealcohols consish in part, of linalool.I'hetiols : A-l b s r t i c r of lliosplieml.When the original oil, after being washed successively withsodium carbonate solution and sodium hydrogen sulphite solutionto remove acids and aldehydes, was treated with 5 per cent.solution of sodium hydroxide, an absorption amounting t o only0.2 per cent. took place. On acidifying the solution and extractingwith ether, a phenolic substance was obt'aiiied, but in too small aquantity t o admit of investigation; this product did not give anydistinctive coloration with ferric chloride. No evidence could beobtained of the presence of diosphenol.Ethers : ITdeiz,fification of illethylchauicol.A fraction of the oil, boiling a t 213--218O, was found to consistof methylchavicol, which was identified in the following way.The fraction was heated with 20 per cent.alcoholic potassiumhydroxide solution for two days in a sealed €ube at ZOOo. Thecontents of the tube were diluted with water and extracted withether. After drying the ethereal solution with anhydrous sodiumsulphate, and removing the &her by evaporation, i t was foundthat the oil had been convert'ed alniost quantitatively into anethole,which boiled a t 232-234O, and solidified on cooling to a mass ofcrystals, melting at 2 2 O . The product possessed the' odour andsweet taste characteristic of anethole.Determinations of methoxylin the origiiial oil gave results indicating the presence of 21.4 percent. of methyl ethers (calculated as methylchavicol) :0.2770 gave 0.0947 AgT. OMe =4*51 or CgHg-OMe= 21.5 per cent.0.2895 ,, 0.0980 AgI. OMe=4.46 ,, C9Hg*OMe=21*3 ,, ,,Constituents of High Boiling Point.The fraction which distilled a t 230-245O was brownish-yellow,viscous, and had a somewhat empyraumatic odour; it probablycontained sesquiterpenes, together with polymerides and decom-position producte of myrcene, due to the high temperature t o whichit had been heate,dVANSTONE : SODIUM AMALGAMS. 2617Sicntmnry of Results.The results of this investigation indicate that the volatile oil ofBarosma venusta leaves has approximately the following com-position :Per cent.Hydrocarbons, chiefly or entirely myrcene .................. 43.0Phenols .................................................................. 0.2Phenol ethers, methylchavicol .................................... 21.414.3Esters (calculated as C,,H,;OAc) ................................. 2.2Sesquiterpenes, loss, etc. (by difference) ..................... 18.4I n conclusion, reference may be made t o an examination ofthis oil by Jensen (Pharm. J., 1913, [iv], 36, 60). Although theleaves from xhich he distilled tqhe oil were obtained from the, samesource as those used in the present investigation, t,he results showcertain differences, of which the1 most remarkable is that he1 found16 per cent. of chavicol, whereas the authors have not been ableto detect the presence of even a trace of this phenol.............. Aldehydes, 9 9 ,, ,, anisaldehyde.. 0.5Alcohols, partly linalool (calculated as C,,,H,,'OH) .........The authors desire t o express their thanks to Mr. J. C. Earlfor much valuable assistance in the pre,liminary stages of thisinvestigation.SCIENTIFIC AND TECHNICAL DEPARTMENT,1 bI PERIAL INSTITUTE, 8. w

ISSN:0368-1645    

DOI:10.1039/CT9140502613

出版商:RSC    

年代:1914

数据来源: RSC