NOTES A Reference Solution for Electrical Conductance Measurements to 800" and 12,000 Bars. Aqueous 0.01 Demal Potassium Chloride
by Arvin S. Quist, William L. R/Iarshall, Reactor Chemistry Division, Oak Ridge National Laboratory,' Oak Ridge, Tennessee 37830
2241 pressure for the different sets of measurements from our laboratories. The literature references are included; these also contain descriptions of the conductance cells and experimental techniques.
Table I : Summary of Electrical Conductance Measurements on 0.01 Demal (or 0.01 Molal) Aqueous KC1 Solutions at Elevated Temperatures and Pressures Temp
E. U. Franck, and W. von Osten Institut fiir Physikalische Chemie und Elektrochemie der Universitat, 76 Karlsruhe, West Germany (Received January 28, 1970)
I n recent years there has been much interest in the behavior of aqueous electrolyte solutions a t high temperatures and pressures.2 Experimental investigations of the properties of water and aqueous solutions have been greatly facilitated by the availability of new alloys that retain excellent mechanical strength a t temperatures to 800" and above. Consequently, many measurements have been made on aqueous systems a t supercritical temperatures and pressures. Since one of the simplest and most direct methods of investigating the behavior of ions in solution is the measurement of the electrical conductances of the solutions, several of these researches have been concerned with the measurement of this property. I n view of the interest in conductance measurements a t high temperatures and pressures, it seems desirable to establish a "reference" solution t o permit direct comparison of the results obtained in different laboratories. Establishing reliable conductivity values for such a solution a t these high temperatures and pressures would also allow direct experimental determination of cell constants under these conditions. A 0.01 demal KC1 solution (defined as 0.745263 g KC1/1000 g solution3) appears to be an appropriate choice as the reference solution for conductance measurements a t high temperatures and pressures. This solution has been used for many years as a standard solution for cell constant determinations near 25" and atmospheric pressures3 Since aqueous KC1 is both stable and a relatively strong electrolyte a t supercritical temperatures and pressures, this solution would also appear to be suitable for use as a reference solution at these high temperatures and pressures. I n recent years many conductance measurements have been made on either 0.01 demal or 0.01 m KC1 solutions a t temperatures to 1000" and a t pressures to 12,000 bars. These measurements have been performed in the authors' laboratories over a period of years using several different designs of conductance cells and pressure vessels. Table I summarizes the ranges of temperature and
Investigators
Franck" Hensel and Franckb Franck, Hartmann, and Hensel' Ritaert and Franckd Mangold and Franck" Renkert von OstenO Quist and Marshallh
range, OC
Max pressure, bars
250-750 45-130 45-220
2,500 8,000 8,000
200-750 300-1000 200-350 200-400 0-800
6,000 12,000 8,000 8,000 4,000
a E. U. Franck, 2. Phys. Chem. (Frankfurt am Main), 8, 92 (1956). F. Hensel and E. U. Franck, Z . Naturforsch., 19a, 127 (1963). ' E. U. Franck, D. Hartmann, and F. Hensel, Discuss. Faraday Soc., 39, 200 (1965). G. Ritzert and E. U. Franck, Be?. Bunsenges. Phys. Chem., 72, 798 (1968). E K. Mangold and E. U. Franck, ibid.,73,21 (1969). H. Renkert, Diplomarbeit, Karlsruhe, 1965. ' W. von Osten, Diplomarbeit, Karlsruhe, 1966. A. S. Quist and W. L. Marshall, J . Phys. Chem., 73, 978 (1969), plus additional unreported measurements totaling 55 separate runs.
'
The experimental measurements were generally made a t many different pressures a t a constant temperature. Values of specific conductances a t integral pressures, at the experimental temperatures, were obtained by interpolation. Some of the studies listed in Table I were carried out using 0.01 m rather than 0.01 demal solutions. However, minor corrections were applied so that the specific conductances could be correlated as based on 0.01 demal KC1 solutions. The measurements on KCl solutions from the sources listed in Table I were combined by plotting isobaric specific conductances vs. temperature and drawing a smooth curve through these data point^.^ Smoothed values for the specific conductances of 0.01 demal KC1 solutions are presented in Table I1 a t pressures from (1) Operated by Union Carbide Corp. under contract with the U. S. Atomic Energy Commission. (2) See, for example (a) E. U. Franck, Endeazour, 27, 55 (1968); (b) J. W. Cobble, Science, 152, 1479 (1966); (c) W. L. Marshall,
Rev. Pure A p p l . Chem., 18, 167 (1968). (3) G. Jones and B. C. Bradshaw, J . Amer. Chem. Soc., 55, 1780 (1933). (4) The earliest values of Franck (Table I, reference a ) were omitted
in this comparison because the uncertainty in these reported values was significantly larger than for those in the other references listed in Table I.
Volume 74, Number 10 May 14, 1970
NOTES
2242 Table 11: Specific Conductances (ohm-' cm-') X los of 0.01 Demal KCI Solution a t Integral Temperatures and Pressures Pressure,
_-----------------
---_____
Tamp, C----------------
bars
100
150
200
250
300
350
400
450
500
600
700
1,000 2,000 3,000 4,000 6,000 8,000 10,000 12,000
368 364 358 351 338 326
498 491 483 481 466 446
599 593 585 574 555 536
663 659 651 640 617 598
689 698 695 687 665 645 625 601
685 707 715 712 699 679 665 644
650 701 718 723 722 703 690 674
578 679 709 724 733 716 707 694
460 643 689 714 732 72 1 711 704
125 516 625 670 707 711 709 703
336 528 610 672 692 694 688
... ...
...
...
... ...
...
~ . .
1000 t o 12,000 bars and a t temperatures from 100 t o 800". These data are presented in graphical form in Figure 1, where specific conductances are plotted as a function of temperature a t pressures from 1000 to 12,000 bars.
7
800
...
.
.
#
116 405 526 628 664 675 673
increasing pressure and temperature. The probable uncertainty of about 0.5% at 100" and 1000 bars increased to approximately 1% a t 8000 bars a t this temperature. At higher temperatures the uncertainty was estimated to be near 1-1.5% a t low pressures but in the region 10,000 to 12,000 bars it had increased to 3-4% a t 800". The uncertainty was greatest under conditions of temperature and pressure where the absoIute value of the conductance was relatively low. For example, a t 800" and 2000 bars the uncertainty may be as large as 5%.
Table I11 : Specific Conductances of Aqueous 0.01 m KC1 Solutions at Saturation Vapor Pressures at Temperatures to 306"
Temp,
TI'C)
Figure 1. Specific conductances of 0.01 demal KCI solutions at integral temperatures and pressures.
In general, the results from Oak Ridge and Karlsruhe were in excellent agreement. Up t o temperatures of 300" the scatter of the two sets of data about a smooth curve drawn through the combined results was generally less than 1%. Above 500" there was somewhat more scatter, but even so the differences in the two sets of data were usually less than 1% except a t low pressures where the absolute values of the conductance had decreased considerably. The greatest differences between the Oak Ridge and Karlsruhe values were a t temperatures near 400" a t 1000 bars. Under these conditions the Oak Ridge data were up t o 5% higher than the Karlsruhe results. The difference decreased with increasing pressure until a t 4000 bars at 400" it was only about 1.5%. Estimated uncertainties associated with the specific conductances reported in Table I1 tend to increase with The Journal of Physical Chemistry
Speoific conductance, Pressure, ohm-1 om-'
OC
bars
x
25
I
140.9"
50
1
212b
100
1
35ab 362" 496b 496d 512c
150
4.8
156
5.6
106
Temp, O C
Specific conductance, Pressure, ohm-1 cmbars x 105
200
15.6
603b 60jd
218
22.3
630"
225
25.5
635b 637d
281 306
65.2 93.4
668' 654'
a Calculated from the equation of J. E. Lind, Jr., J. J. Zwolenik, J . Amer. Chem. Soc., 81, 1557 (1959). A. J . and K. M. FUOSS, Ellis, J . Chem. Soc., 2299 (1963). A. A. Noyes, et al., "The Electrical Conductivity of Aqueous Solutions," Publication No. 63, Carnegie Institution of Washington, Washington, D. C., 1907; A. A. Noyes, et al., J. Amer. Chem. Soc., 30, 335 (1908). Interpolated by Ellisb from Noyes' data.'
In general, the apparatus a t our laboratories were not designed to give conductances along the liquid-vapor curve which were as accurate as those previously reported by other investigators. Thus the values reported in Table I11 for specific conductances of 0.01
2243
COMMUNICATIONS TO THE EDITOR nz KC1 to 306" a t saturation vapor pressures are those
of earlier researchers but have been included here for completeness. These specific conductances of KC1 presented in Tables I1 and I11 are believed to represent the best
values presently available for high temperatures and pressures. It is hoped that they will be useful in establishing the reliability of other conductance apparatus and in obtaining cell constants a t high temperatures and pressures.
COMMUNICATIONS TO T H E EDITOR Dielectric Constants of Alcoholic-Water Mixtures at Low Temperature
Sir:
I n 1932, Akerlof published experimental values for E, the dielectric constants of hydro-alcoholic solvents, as a function of temperature between 0 and
law to low temperature. Using a classic method for obtaining dielectric constants5 we measured capacity of a cylindrical condenser by means of General Radio 716 C bridge with 300 kHz for frequency. The lowtemperature control device has already been describeda6 By this method we have studied different methanolwater mixtures, methanol-ethanol-water (56 :25 :20,
Table I : Dielectric Constants of Alcoholic-Water Mixtures as a Function of the Temperature
____-_-_-_________-
OC
Tm -e--p-------Mixtures
+20
+10
0
-IO
-20
-30
-40
-50
Methanol Methanol-water 80%-20% Methanol-water 70%-30% Methanol-water 60%-40% Methanol-water 50%-50% Methanol-water 40%-60% Water Methanol-ethanol-water 55%-25 %-20 % Ethylene glycol-water 50%-50%
33.6 43.7
35.4 46.4
37.9 49.5
40.6 52.3
42.7 55.4
45.4 58.6
48.3 61.9
51.3 65.7
46.3
49.4
53.0
56.6
60.1
63.5
66.8
55.1
58.7
62.5
66.0
70.5
73.8
60.3
64.0
67.8
71.2
75.5
63.8
67.7
71.9
75.6
80.4 43.0
84.2 45.7
88.1 48.6
64.5
68.4
72.4
-70
-SO
-90
-100
54.6 69.3
58.0 73.5
62.0 77.8
66.5 82.8
88.4
70.9
74.9
79.2
83.5
88.7
94.0
78.2
82.2
86.7
92.05
97.5
103.8
79.2
83.9
87.9
92.5
79.5
83.5
87.9
51.2
54.6
57.9
61.4
65.3
69.0
73.5
78.3
83.7
76.5
80.7
85.0
89.3
94.0
98.8
Table 11: Coefficients a and b of Akerlof's Law: log
e
=a
-80
89.7
- bT, Where T is the Temperature in "C ..&.^ "*.
U
b X 10s
Methanolwater 70%-30%
Methanolwater 80%-40%
Methanolwater
Methanol
Methanolwater SO%-ZO%
1.580 2.65
1.695 2.50
1.730 2.45
1.790 2.50
+60°. He obtained the following relation: log E = - bT. Freed and Bielski2 showed that it is possible to dissolve proteins at low temperature (7' < 0') in without providing the extrapolated value of r is approximately that of water _ _ a t room temperature ( E N 80). We have further developed the use of this technique in our laboratory.sj4 I n view of the great importance of E , we decided to check experimentally the extrapolation Of Akerlof's a
Methanolethanolwater
Ethylene glycolwater
50%-50%
Methanolwater 40%-60%
Water
20%
50%-50%
1.830 2.30
1.855 2.20
1 945 2.00
1.680 2.65
1.860 2.65
55%-25%-
I
v/v) and ethylene glycol-water (50:50 v/v).
The
G. Aker16f, J. Amer, Chem, sot,, 54, 4125 (1932). (2) B. Bielski and S. Freed, Bwchim. Bwphys. Acta., 89, 314 (1964). (3) T. Shiga, M. Layani, and P. Douzou, Bull. Soc. Chim. B i d , 49, 507 (1967). (4) R. Banerjee, P. Douzou, and A. Lombard, Nature, 217, 23 (1968). (5) A. R . Von Hippel, "Dielectric Materials and Applications," wiley, New Yo&, N. Y . , 1954. (6) G. Hui Bon Hoa, and C. Balny, J. Chim. Phys., 66, 1528 (1969). Volume 74, Number 10 May 1.1, 1970
