June, 1948
CONDUCTANCE OF STRONTIUM
Control of temperature should be maintained to prevent (1) distillation of solvent from the paper to the walls of the chamber, (2) disruption of the single phase solvent system; also because temperature has an effect on the constancy of the RF values. The authors express thanks to Dr. John T. Edsal1for the interest he has taken in this work.
[C’ONTRIBUTION FROM
THE
HALIDESIN
AQUEOUS
ETHANOL
3137
SUmmrUy 1. A study of partition chromatography with applied voltage has been presented. 2. Rp values for ten amino acids obtained under the experimental conditions are given. 3. Paper buffered with phosphate a t pH 6.2 has been used. BEVERLY, MASSACHUSETTSRECEIVED MARCH16, 1948
KEDZIECHEMICAL LABORATORY, MICHIGAN STATECOLLEGE]
The Electrical Conductance of Strontium Chloride and Strontium Bromide in EthanolWater Mixtures BY RICHARD LOUIS BATEMAN AND DWIGHT T. EWING from concentrated sulfuric acid (20 ml. of acid per liter of alcohol) to remove amines. The distillate was then treated with alcoholic lead acetatea (3 g. of lead acetate in 5 ml. of water and theti 5 g. of KOH in 25 ml. of alcohol) and distilled. Absolute alcohol was then prepared by treating each liter of distillate with fresh calcium oxide (200 g. per liter of alcohol), refluxing and distilling. In these distillations, the first and last portions of distillate were discarded. The water content was determined by density measurement and reference to standard density tables.? The alcohol thus obtained was 99.9% absolute and had a specific conductance of 2.0 X lo-’ mho a t 25’. Conductance water was prepared by distilling water containing a little potassium permanganate through a block tin condenser. About 50% of the distillate was allowed to condense and only the middle fraction was retained. At 25” the specific conductance of this water was 1.OO-1.04 X mho. Apparatus.-A Leeds and Northrup Kohlrausch slide wire bridge with extension coils, tunable head phones, Curtis coil resistance boxes, adjustable air condensers and Leeds and Northup audiooscillator were used. All Darts of the bridge assembly were protected by properly grounded shields. A thermostat bath filled with water was kept constant to within 0.01 ‘during the series of measurements. Temperature measurements were made on a thermometer (No. 23044) that had been certified by the Bureau of Standards (c-trtificate NO. 49571). Temperature fluctuations were followed by a Beckmann thermometer. The conductance cells were of the Jones and Bollinger8 type with the dling tubes widely separated. The electrodes were not platinized.@ The primary qtandard solution for cell constants was the 0.01 demal KC1 solution of Jones and Bradshaw.’O Cells having low constants were caliExperimental brated using a more dilute solution which had been comPurification of Materials.-J. T. Baker C. P. SrC12.6- pared to the standard 0.01 demal KCl in another cell. Procedure.-The ethanol-water solvents were prepared HnO was recrystallized from conductance water once above and once below the transition temperature (61.34’) by the by the weight method. The electrolytic solutions were method of Richards and Yngve* and oven-dried t o con- prepared in volumetric flasks after attaining thermal equilibrium in the thermostat bath. The conductance stant weight. J. .T. Baker C. P. KCl designated “special crystals” cells were rinsed several times with the appropriate solu(low in Ca, Mg and “,OH ppt.) were twice recrystallized tion, brought t o thermal equilibrium and the conductance from conductance water. T h e s d t was then partidly fused determined. All final readings were taken near the center in a platinum crucible and transferred to a closed bottle of the bridge with the air condensers adjusted for the most satisfactory null-point. The cells were selected so that while still hot. Ethyl alcohol was purified by distilling 95% alcohol the resistance was ordinarily above 1000 ohms. Duplicate determinations were made from two independently pre(1) This paper represents part of a thesis submitted by Richard pared solutions. The conductance of the solvent was deLouis Bateman to the Graduate Faculty of Michigan State College termined immediately before the preparation of the der-
The earliest investigations of electrical conductance in mixed solvents were those of Lenz,2and S t e ~ h a n . This ~ type of work was extended by other workers and particularly by Jones and coworkers.4 In general, these investigations showed that the conductance of electrolytes in mixed solvents decreased as the solvent viscosity and degree of solvation became greater but increased as the dielectric constant of the solvent and temperature became greater. A large part of these early investigations concerned the uni-univalent electrolytes with less attention given to those of higher valence types. No recorded data are given for the conductance behavior of strontium chloride and strontium bromide in ethanol-water mixtures. The purpose of the present investigation was to determine the influence of concentration, solvent composition and temperature on the conductance behavior of strontium chloride in ethanol-water solutions and to note the influence of viscosity and dielectric constant of the solvent on the conductance of these solutions. For purposes of comparison, a limited amount of work was also done on the conductance of strontium bromide in ethanol-water solutions.
in partial fulfillment of the Ph.D. degree, June, 1944. (2) R. Lenz, Mcm. de I’Acod. de SI. Pdersboutg, 7, 30 (1882). (3) C. Stephan, W i d A n n . , 17, 678 (1882). (4) H. C. Jones land co-workers, Carnegie Inst. Reports; No. 80 (ISW), No. 180 (1913) and No. 210 (1916). (6) Richardraad Yngve, Txrs JOURNAL, 40.81 (1918).
(6) S.Zczalts, Ind. Eng. Chrm., 90, 493 (1928). (7) “International Critical Tables,” 8, 118 (1928). (8) Jones and Bollinger, THIS JOURNAL, 66, 1780 (1933). (9) J. R. Partington, J . Chrm. SOC.,99, 1937 (1911). (10) Jones and Braduhnw, T x t a JOURNAL. 68, 1780 (1933).
RICHARD LOUIS BATEMAN AND DWIGHT T.EWING
2138
trolytic solution and the conductance of the solvent waa subtracted from the specific conductance of the solu-
tion.
TABLE I J~QUIVUENT CONDUCTANCEOF S T R O CHLORIDE ~ IN ETRANOL-WATBR M n r ~ o a s AT s 25' Cb
%Ethanol
0.1OOO .OW ,0250 .0100 .#50 .0025 .0010
.oooo
0
101.6 107.9 113.9 120.4 124.2 127.2 129.6 134.5
C
60
0.1Ooo
23.54
.OW
A 0" 5
85.5 90.7 95.8 102.3 105.2 108.4
...
115.0
20
40
53.1 56.50 69.89 64.67 66.33 68.23 69.38 71.7
33.84 36.44 39.18 43.24 45.45
46.54 48.53 50.8
90
90.89
80
15.31 17.51 20.19 24.57 27.51 30.96
...
26.05 13.17 .0250 28.74 15.44 .0100 33.12 19.38 .0050 35.62 22,23 .0025 37.87 25.76 .... 30.73 .0010 40.96 41.4 44.2 37.4 * & = ohm-' X cm.' X equivalent-'. matity.
.oooo
Vol. 70
TABLEI1 BROMIDE IN ETHANOL-WATER Mnrroass AT 26 O
m W I V A L B N T CONDUCTANCE OF -0-
C
% Ethanol
0
0.1Ooo
4 . .
.OW
110.4
... ...
.02m
.om
122.9
.0050 .0025
130.1 134.0 137.7
.#lo
.oooo
ti
60
36.02 38.71 41.13 44.31 45.83 47.76 49.45 51.9
26.92 29.15 31.74 35.14 37.54 39.73 42.13 45.5
...
TABLEI11 EQUIVALENT CONDUCTANCE OF 0.01 NORMAL STRONTIUM CHLORIDE IN ETHANOL-WATER MIXTURES AT 20.25 AND 30 O
...
%Ethanol
0
20 25 30
106.7 120.4 131.6
...
9.75 11.80 14.27 16.92 22.1 C = nor-
Temp., OC.
A0
40
80
99.89
35.81 43.24 49.28
21.10 24.57 26.40
8.59 9.75 10.76
large scale and the values for A,, were obtained by graphical extrapolation. As one might expect, the values of both Ac and ho decrease as the percentage of ethanol becomes larger. Discussion Figure 2 shows the influence of solvent compoFigure 1shows the influence of concentration on the equivalent conductance of strontium chloride sition on the equivalent conductance of 0.001, in various ethanol-water mixtures a t 25'. The 0.005, 0.025 and 0.100 normal solutions of stronabsence of experimental transference data for the tium chloride. Increasingly larger percentages ions in these solutions made it unfeasible to evalu- of ethanol cause progressively smaller change in ate &I with the aid of the Onsager equation." the equivalent conductance up to a point of inflecCurves similar to those in Fig. 1 were drawn on a tion. Beyond this point, the change in equivalent
*
0.1 0.2 0.3 Square root of concentration. Fig. 1.-Equivalent conductance of strontium chloride in ethanol-water mixtures at 25': A, 99.89%; B, 90%; C, 80%; D,So%; E,40%; F,20%; G,5% and H. 0% ethanol in solvent. 0
(11) L. Onanger, Physik. Z.,37, 888 (1926);
a,277 (1927).
0 40 80 Weight per cent. ethanol in solvent. Fig. 2.-Equivalent conductance of strontium chloride in ethanol-water mixtures a t 25O: A, 0.1 N; B, 0.025 N; C, 0.005 N and D, 0.001 N.
CONDUCTANCE OF STRONTIUM HALIDES IN AQUEOUS ETHANOL
June, 1945
2139
conductance becomes progressively greater as the percentage ethanol increases. An explanation for this might be: in the less alcoholic solutions the change in viscosity is the most significant factor influencing conductance while in the more alcoholic solutions the change in dielectric constant is more significant. Between these two extremes, the two solvent properties are of about equal importance in influencing the conductance. Also, for an electrolytic solution of this type, the ionic “sizes” should vary with solvent composition giving a corresponding influence on conductance. From this, it would follow that Walden’s d e l 2 (Aoq = constant) should not apply very accurately. The quantity Aoq/D has been applied to electrolyte^^^ and in the present case this quantity is more nearly a constant value than Aoq. Table IV gives Ao, Aoq and Aoq/D for strontium chloride in different ethanol-water mixtures a t 25’ in which 7 is the viscosity and D is the dielectric constant of the pure solvents. TABLEIV LIMITINGCONDUCTANCES OF STRONTIUM CHLORIDE AT 25 ’ ETHANOL-WATER MIXTURES 7in ’ Ethanol solvent
0:
poise
A(
Db
Aorl
0
IN
Ar/D
134.5 0.00895 7 8 . 5 1.204 0.0153 115.0 .01087 75.6 1.250 ,0165 71.9 .OB08 67.0 1.300 ,0194 50.8 .02374 55.0 1.206 .0219 40 44.2 .02232 43.4 60 .986 .0227 41.4 .01738 32.8 .719 .0219 80 90 37.4 ,01422 28.1 ,532 .OB9 99.89 22.1 .01104 24.2 .244 .0101 a “International Critical Tables,” 5, 22 (1929). b G. Akerlof, THIS JOURNAL, 54, 4133 (1932).
0 5 20
20 40 60 80 100 Weight per cent. ethanol in solvent. Fig. 3.-Curve A, the fluidity and curve C, the dielectric constant D of ethanol-water mixtures at 25”: Curve B, the limiting equivalent conductance AO and curve D, the conductance viscosity product A o ~for strontium chloride at 25’.
From Table I V it may be observed that A o ~ / D is relatively constant for solutions containing between 20 and 90% ethanol in the solvent. Figure 3 illustrates, a t 25O, the dependence of A0 and Aoq on the composition of the solvent for strontium chloride solutions and gives the values for the viscosities and dielectric constants of the pure solvents. Figure 4 shows the influence of temperature on the equivalent conductance of 0.01 normal solutions of strontium chloride in four dif€erent solvent compositions. In all cases the temperature coeffi-
+
cients are positive and become less as the temperature increases. From tangents to these curves at 25’ the information in Table V was obtained.
120
TABLEV TEMPERATURE COEFFICIENT OF CONDUCTANCE OF 0.01 NORMAL STRONTIUM CHLORIDE IN ETHANOL-WATER MIXTURES AT 25”
A
% ’ Ethanol
1
in solvent
A
dA/dT
(dA/d T ) l A
99.89
9.75 24.57 43.24 120.3
0.20 .51 1.47 2.55
0.0232 .0208 .0340 .0125
80 40 0
(12) P. Walden. 2. physik. Chrm., 55, 207, 246 (1806). (13) Van RpsPelberghe and Fristom. Tma JOURNAL. 67, 680 (1845).
