May, 1945
CONDUCTANCES OF LITHIUM, SODIUM AND POTASSIUM PERCHLORATES [CONTRIEUTXON FROM
The Electrical Con.'
855
THE CHEMICAL LABORATORY OF INDIANA UNIVERSITY]
ance of Aqueous Solutions. II. Lithium, Sodium and Potassium Perchlorates at 25' '
BY JAMESHOMER JONES
++
LiClOd 0.9971 0.0623m = density The measurements of Davies atid Robinson' on NaC10, 0.9971 0.078% = density the electrical conductance of dilute solutions of KClO, 0.9971 + 0.0863~~ = density thallous perchlorate, and those of Van Rysselberghe* on magnesium perchlorate are apparently 'where m refers to the concentration expressed as the only ones made on metallic perchlorates in moles per lo00 g. of solution. No recorded values water a t 25' since 1926. Some of the earlier were found for comparison. measuremenis a t 25' on the perchlorates here Data studied are listed in the footpotes.a All solutions were prepared either directly by. Since the earlier measurements disagree considerably, the electrical conductances of lithium, weighing the salt and the water, or by weight dilusodium and potassium perchlorates have been re- tion, All weights were corrected to vacuum. The cell constants were determined using the standards determined. The limiting conductance of the perchlorate of Jones and Prendergast? The observed values for the conductances of ion in water a t 25' was assigned a value of 67.94 by Daviesl based on the conductance of thallous solutions of various concentrations are given in perchlorate. Lange' in his review assigns a con- Table I where t is the molar concentration and A ductance of 67 to the perchlorate ion which is the is the equivalent conductance. same value listed by Davies in his book on conTABLE I du ctance.
Experimental Apparatus.-The apparatus used has been described in an earlier paper.' The cell constants of the conductance cells were redetermined and found to be substantially unchanged. The platinkation of the electrodes was checked by measuring the resistances of the cells at 600,lo00 and 2000 cycles per second and found to be adequate. The icepoint of the platinum resistance thermometer was checked periodically. The individual dial resistors for the hundred-ohm dial and the thousand-ohm dial were checked against standard resistors calibrated by the Bureau of Standards. The values for the one ohm dial and 10 ohm dial were accepted at face value. T h e values of the resistances measured were kept above lo00 ohms whenever pcyible. The temperature control approximates *0.001 Purification of Materials.-Best grade potassium perchlQrate was recrystallized'twice from conductivity water, dried a t 250' and stored in a vacuum desiccator. Anhydrous sodium perchlorate was recrystalliz;d twice from butanol, washed thoroughly with dry ether and then dried at 250' and stored. The lithium perchlorate was made from pure lithium carbonate and perchloric acid. The lithium carbonate was purified by solution in hydrochloric acid and precipitation with resublimed ammonium carbonate and ammonium hydroxide. The solution of lithium perchlorate was evaporated until i t solidified on cooling and was then fused in platinum. Each sample was freshly fused in a Elathum boat a t 300-350' before using.
.
Density of the Solutions.-The dqnsities of several solutions of each of the salts were determined a t 25'. The data may be represented within 0.01% by ineans of the equations (1) C.W.Daviu and R. A. Robinson, J . Cham. Soc., 574 (1937). (2) Pierre Vnn Rysrelberghe and J. M. Magee, TEXS J O ~ N A L 65. , 737 (1943). (3) (a) Harry C.Jones, Came& Institute Bulletin No. 170 (1912); (b) Noyes, Boggs, Fame11 and Stenqrt, Tma JOURNAL, 13, 1654 (1911); (c) Ostaald, "Lehrbuch der dlgemeinen Chemic." 18011905. (4) Jh Lange, 2. ghysik. C h a . , Al88, 284-315 (1941). (5) C. W. Davies, "The Conductivity of Solutions," John Wilw nnd Sons, Inc., New Yo&. N.Y.,1933,p. 208. ( 8 ) J. H.Jon-, TUX8 JOUENAL, 66, 111s (1944).
EQUIVALENT CONDUCTbNCES OF SOLUTIONS AT 25" LiCIOi C
0.10544 .090362 .OS170 .064896 .049409 .034482 .020391 .017555 .011891 ,0050844 .0044629 .0020410 .0009874 ,0006777
NaCIOi RClOi A C A C A 88.17 O.OQ9SOl 98.63 0.10696 114.90 89.08 .076764 100.00 .OS3130 117.18 89.59 .Ob3993 101.99 .075068 118.90 90.98 .038510 103.80 .OX3458 121.10 92.43 .031954 104.73 ,029702 125.35 93.95 ,020353 106.90 ,028163 125.59 98.12 .012634 108.76 ,023838 126.95 98.60 .00900b9 109.96 ,018222 128.40 98.06 .0048058 111.86 ,014315 129.70 180.51 ,0041725 112.14 .010131 131.40 100.85 ,0027320 113.20 ,009089 131.88 102.41 .OOl3613 114.38 .0087067 132.06 103.54 .0007151 115.30 .0077881 132.64 103.91 .0064104 133.28 .0040361 134.82 ,0031150 135.58 ,0025208 136.08 .0015280 137.22 ,0007355 138.26 .00051512 138.74
Discussion The limiting conductances of these salts were determined first by the Shedlovskys relation that plots of
are usually straight lines for strong uni-univalent electrol*s up to concentrations of about 0.1 molar. Table I1 summarizes the observed and calculated values for A a t rounded concentrations. Figure 1 shows the plots of the Shedlovsky function. It will be noted that potassium perchlorate does not behave in the manner predicted by the Shedlovsky equation. The much lower slope and the (7) Grinnell Jona .ndM. J. hndergast. iMd., Sa, 731 (1937). (8) T. S h e d l a L y . W.,U,1406 (1932).
856
HOMER Josss
JAMES
TABLE I1 LiClOI
NaC10' obs. calcd. 115.64 115.58 114.87 114.82 113.811 113.7i 1 1 1 7.; 1 1 1 77 109.;!l 109.(i5 106.9Ii 106.94 102.40 102.39 100.52 100.4!1 9R.43 98.4!)
ob. calcd. 104.18 104.11 103.44 103.42
C
0.0005 ,001 ,002 ,005 .010 ,020 ,050 ,070 . 100
102.46 102.44 100.57 1 O O . , j 5 98.61 98.61 96.18 96.19 92.20 92.38 90.52 90.96 88.56 .... An 21
2
A
I.JO.?):
127.!12 127.9fl 121.li3 121.(iO 118,7!l 118 77 11.;
211
113.2;
A0
B = 112.0
-
131.46
= 117.48 .A,, = 1 4 0 . 0 4 A = 87.22 .I =: 9 2 . 3 7 E = 92.6 H = 4') 0 f Bc(1 -- 0.2294d/r)
I!)5,98 b-i.52
A = A0
KClOr ralcd. 13X.76 137.99 137.8i 137 l i 18ti,IL? 1Rti.Oll lY4.1ti t,{:L74 obs.
d
C
deviatioii upwayd of the curve in dilute solutioiis 'have been observed in a good rnany other potassium salts such as potassium nitrate, potassium bromate aritl potassium chlorate. Even potassium chloride shows ;t slight upward deviation in dilute solutions froin tlic predicted straight line. Two checks were made to insure that the measured contluct~nceswere correct. First, a riew sample of j~ot~tssiuiii perchlorate was obtainctl antl the coilductmces d tlilutc~solutions were redcterniinetl with good cliccks. Secondlj-, t w s u l u t i ~ i ~ois sodiuiii chloride (O.05maritl 0.0lnz) were p-eparetl aiid their equiv:ilent conductances tleterlniiied ~. I liese clieckcd the equivaleiit cont1uct:uices rei)
