THE ELECTRICAL CONDUCTIVITY OF METHYLAMINE SOLUTIONS. BY
E. C. FRANKLIN A N D H D. GIBBS. Received July
12,
1907,
Since methylamine has been shown to possess a rather wide solvent power,' and to give solutions which in some cases are possessed of marked electrical conductivity,* it has been deemed worth while to extend the work of Gibbs on the properties of methylamine, to a quantitative study of the electrical conductivities of the solutions. T h e plan had been formulated of making measurements on a selected list of solutions, chosen to cover the field as well as possible, but as an unfortunate result of the earthquake of last April, the investigation was brought to a sudden close just as the work of making the measurements was well under way. I t has been the expectation of the authors to take up again this investigation and finish a rather extended series of observations before publishing, but as a result of the junior author's transferring his field of activities to the Philippines, it has been determined to publish the data so far obtained. Descr@fio)i of the Appara tus, Method of
[email protected] apparatus employed was, in principle, essentially the same as that used by Franklin and K r a u ~in , ~their measurements of the conductivity of liquid ammonia solutions, with such modifications as the nature of the solvent seemed to require. A is a steel cylinder containing the stock of methylamine. C is a filter tube which is introduced into the train for the purpose of removing any solid impurities which might be carried over with the gas.' B is a manometer used as an aid in regulating the flow of gas. D is a receiver into which the gas is condensed and retained until the pure liquid is required in the conductivity cell. E is the conductivity cell with its connections. E' is the constant temperature bath of ice and water. F is a receptacle for receiving the solution after removal from the conductivity cell. Before beginning a series of measurements this tube is evacuated through the stop-cock, So,and is kept cool by a bath of liquid ammonia. After a series of measurements is finished, F is removed and sealed before the blow pipe, thus permitting the operator to recover the expensive solvent. G is a pressure regulator devised for the purpose of regulating the boiling point of the solution in the conductivity cell, E, to the temperature of the bath, E . T h e tube from the stop-cock, S', delivers the gas through pin hole openings under the mercury column, G, which latter may be adjusted to any desired height. T h e methylamine which escapes from the conductivity cell by way of this pressure
' Gibbs, This Journal, 28, '395.
' Gibbs, loc. cit., and Franklin and Kraus, Am. Ch. J., 24, go. Am. Ch. J . , 23, 277. Vide Franklin and Kraus, Am. Ch. J., 23, 278.
1390
E. C . F R h S K L I S A N D € I .
I). GIHIjS
regulator is condeiised in the cell H,which at the end of a series of measurements is removed and sealed. thus effecting :i saving of the methylamine. Liquid aiiiiiioi1i;t for contleiisiiig tlic iiictliylaiiiiiie i i i the receptacles D, F aiid H, is delivered from a c:,.linder of the coiiiniercial liquid through the tube I. Xiiiiiioiiia g-as is carrietl to a carbo!, of water i i stirring the soltition a n d through tiie tube 1'. I'ure, d r \ ~l i ~ ~ d i - o g efor removing it from the conductivity cell is delivered t o tlie apparatus under pressure a t the stopcocks SGaiid S". i t i.q to be noted that the nicthylamine after leaving the steel cylinder and tlie short piece of lead tubing leading froiii it, comes in contact oiill. with tlie glass of t h e app:tratus, tlie platiiiuin electrodes of the coiicliictivitj- cell, ant1 the liytlrogen used for stirring tlie solution, for the various glass portioiis of the apparatus are sealed together by nieaiis of flexible joints in:& ljy drn\viiig the tubing to capillaries. T h e hyilrogeii which comes i i i contact ivitli t h e solutions is produced by tlie electrolytic t1ecimi;)osition of dilute sulpliuric acid i i i tlie tube. K , (Fig. 2 ) atid is 1)Lirifii.d 11). passitig throiigli the three \ r a s h bottle..: I,,, I,, m c l I?! containing i i i I,, aiid I,, nil aqueous solution of potassium hydroxide :iiitl pyrogallol^ aiitl i i i I,, coiiceiitrated sulpliuric acid), aiid the three tulje,s. 11,) 112 awl AIs, coiitaiiiiiig rcspectiT.-ely soda-lime. calcium chloride aiid phosphorus peiitoxide. The h y drogeii prcwure is slio~vti12). the iiianometer X. lf'ith this preliiiiiiiary survc!. of ilie a p p r a t i i s , it i d 1 be cas!- to f'ollon~ tlie details of a series of IiieaSLlreiiielits. Operatioiis are beguii b;,. tiran.itig liquic! niiiiiioiiia i i i t o the I k w a r iubes, I), I; :uid €1. T h e 1-alj.c of X is tiieii opeiiecl and iiieth)-laiiii~ieis tli~tiiletlinto the receptacle \\-lielice it is imii tlirough the stol)-cock. S'.iiito the coiitliictivit). ccl! Ilatiiiuiii s y m i i , 1;''. is iiitrodiiced through tlie tubulure, E"'. X i i y partirleb o f tlie solute reiiiaiiiare tlieii iiig attached to the spoilii iir ti, to J i e sides oi' \lie tiil~e,J3'. iraslictl iiito tlic cell by dran-iiig additional ~iit:tl:ylaiiiinefrom the recei\-er. r). The iiitroductioii of solvent is coiitiiiiiec.1 until tlie glass pointer, B'is just submerged. T h e solution i . . tiiciii stirred I,>- ~iieaiisof a stream of hydrogeii througli the stopcocks, 9% S', S', niitl the capillary tube, E, until the solution is hoiiiogeiieous aiid the surface of the solution is adj Listed accurately 011 t h e poi:iter. T h e passage of liydrogeii tliroiigli the solution :md thence by w a ~ of ' the stopcock, Sti to the receil-er. H. Carrie.; metllyiniiiiiie i.npor with i!, t I i ! i i \.iiabliiig the operator to bring about the desired atljustineiit to the 1)oiiitc:r. Since the capil-
E L E C T R I C A L CONDUCTIVITY O F M E T H Y L A M I N E
1391
lary tubes, E and E3,have an appreciable volume, t h e adjustment of the surface of the solution to the pointer must take place with the stopcocks, S 5 and S', set to give gaseous connection between these and the neck of the cell at E. T h e level of the solution within the capillaries will then come into equilibrium with that of the contents of the cell. Corrections for difference in capillarity between methylamine and water, which latter was used in calibrating the cell, have not been made. T h e resistance of the solution between the electrodes, E, is theii measured by the familiar method of Kohlrausch, connection with the exterior being made through the tubes, E', filled with mercury. An aliquot part of the solution is then removed by turning hydrogen under pressure on to the surface of the solution through S', after setting the stopcocks S5, S8,Sg and SIo,to deliver into the cell, F and allowing the solution to flow out until the tip of the J " tube, E', is just uncovered. Fresh solvent is then introduced, and the operations described above are repeated until the desired dilution is reached. 7he Solzient.-The methylamine used in this investigation was a part of a kilogram obtained from Kahlbaum.' I t was purified by distillation after long contact with metallic sodium to remove any water and ammonia, which might have been present. No tests were made to prove the purity of the solvent, although its essential purity is to be assumed from the observed constancy of its boiling point' and the high specific conductivity of the purified liquid. Methylamine of a specific conductivity, K = 0.7 X IO-^ to 1.2 X IO-', was easily obtained in the cell of the conductivity apparatus. S o attempt has been made to determine the conductivity of the purest methylamine. Constants and U?zits.-'I'he units of Kohlrausch have been used.s T h e resistance capacity of the cell at 20.3' was found by means of a fiftieth normal solution of potassium chloride' to be 0.1886 Kohlrausch units. T h e volumes of the conductivity cell, determined by weighing at 16', the amount of water required to fill the cell to the respective glass pointers, are for the points E3 a d E', 3.92 cc. and 7.83 cc. respectively. Numerical Results. -In the foliowing tables are given the results of measurements on the five substances studied. T h e dilutions are expressed in liters per gram molecule, and are denoted by ~ / I O O O .T h e mclecular conductivities are denoted by the symbol A . T4E L E I . -Potassitdm Iodide. +/IO00
21,s
A 12.2
#r'
1000
174. 348.
A
17.9 23.4
43.5 12.2 87.0 14.0 The purchase of this methylamine was made possible by a grant from the Trustees of the Baclie F u n d , to whom acknowledgment is here made. *Cf. Gibbs, This Journal, 27, Sjg. Kohlrausch and Holborn : Leitfahigkeit der Elektrolyte, p. 77.
E. C. FRANKLIN AND H. D. GIBBS
1392 13.5
27.0 53.9 107.5
214.5 12.1
5.9
TABLE z.-Potassium lodide. 13.I 428. 12.4 856. 12.6 I jI0. 14.4 3420. 18.4
TABLE 3.--Acetamide. 0.03I 11.8
24.4 32.7 44.2 64.5
0.030
0.02s
TABLE 4.-BenzenesuZ~honamide. 29.6 0.56 59.1 0.74 TABLE 5 .-.Veta nitrobenz e nesulphonamide. 5.64 33.5 5.30 16.8 TABLE 6.-~ll'elanitrobertzciiesulphonan~ide. 13.4 5.15 106.6 6.88 213.0 3.73 26.7 4.81 53.4 5.40 425.5 15.5 TABLE 7,-SiZver Nitrate. 25.9 10.5 22.1 0.66 1.32 35.3 21.1 19.6 30.8 42.1 '9.4 2.68 5.28 26.4
TABLE 8.-SiZvev Nitrate. 0.61
27.0
35.8
17.8
1.22
33.3
77.5
22.2
2.44 4.87 9.72 19.4 0.24
0.362
0.581
31.5
154.8
26.9 22.8 20.4
309.0
618.0
TABLE 9.--Silver h-ifra fe E;. 14 0.868 17.2 1.2s 26.4
26.2 33.3 44.8
30.4 31.4
Grajkical Rejresentafion of tke Resulfs.-In the acconipanying plate are plotted the results obtained for silver nitrate, potassium iodide and metanitrobenzenesulphonamide in methylamine together with a curve representing the behavior of silver nitrate in amylamine.' T h e molecular conductivities are plotted as ordinates, the logarithms of the dilutions a s abscissas. T h e logarithms of the dilutions rather than the dilutions themselves, or even the cube roots of the dilutions, are used for the reason that this method gives a better distribution of points in the more concentrated solutions. This set of measurements was made with a cell of the following constants : Volume to point I, 2.98 cc. ; point 2, 4.43cc. ; point 3, 7 . 1 1 cc. ; point 4, 10.63 cc. ; point 5, 15.66cc. The cell constant was, 0.1905. Kahlenberg and Ruhoff, J. Phys. Chem., 7 , 254.
ELECTRICAL CONDUCTIVITY O F METHYLAMINE
I393
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I
I
I
I
I
I
h
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I I
I394
E. C. F R A S I < I . I S ANI) I-I.
n.
GIRDS
Uisrussioiz of R e s u l ~ s.-. I t I n s iieeli ilotctl tlint ccrtaiii iion-aqueous of tlirninisliing uiolccsolt1tioiis not infrequently esliiliit tlie pllct1o1ii~~i(~i1 ular conductivity with increasing (liliition,' rll otlicr CR. lar coiitluctivity falls to a i i i i i i i i i i i i i i i , nfter which \\.it11 fiirtlicr tlilutioii it coiidiictivity of rises continuousl\.. Lewis" has foillld that the 1i101rc~ihr potassium iodide i i l liquid iodine :;t first illcreases ivitli tiic dilution to be follo\vetl 11). n striking fall. X similar lwlinvior of ,yilvcr nitrate in amylamine has been 3bserwd by E;nlilenlwrg aiicl I
