200'. For this reason one may expect the function sum in this case to give a considerably lower entropy value than that obtained by the more accurate graphical method. The following combinations were found to fit the experimental data on chromic oxide and chromous chloride to above 100'.
( y )+ (7)(r?) D (g) + ( y ) (y)
C C ~ =~ D O ~ Ccrci2 =
+E
TABLE VI ENTROPY DATA Cr
CrzOa
CrCls
0.22
0.53
3.96
5.46
18.84
24 24
Extrap. (0-56.2),
"K. Graph (56.2298.1), O R .
S'2~8.1graphical 5 . 6 8 * 0.05 S'ZSS.~ calcd. from functions
19.4 18.0
f
0 2
28 2
* 1.0
CrCIz
Extrap. (0-44.7), "K. Graph (44.7-298.1). OK.
6.05 22.36
SOm.1 graphical
27.4 * 0 . 7 27.6
calcd. from functions
s"~88.1
Related Thermal Data Thermal data relating to these materials and the source are given in Table VII. TABLEVI1 THERMAL DATA
f 2E
2E
E
Table V I gives the results of the entropy calculations.
[CONTRIBUTION FROM THE
AHas
4Fonon I
I
sa8 1 This report
Sa8 I
5.68 -288,900" -269,400' 19.4 - 92,750* - 84,00Sb 2 7 . 4 29 7b -129,565' -113,253 2 8 . 2 31.0b,31.2d Roth and Becker, 2. physik. Chem., A145,467 (1930) Doerner, U. S. Bureau of Mines (in press). Calculated from AH208.1 and entropies. Trapeznikowa, Schubnikow and Miljutin, Physik. Z. Sowjetunion, 9, 237 (1936). Cr Cr?Os CrCL CrCls
Summary The heat capacities of chromium, chromic oxide and chromous and chromic chlorides at low temperatures have been determined and their corresponding entropies calculated as 5.68, 19.4, 27.4 and 28.2, respectively. BERKELEY, CALIF.
DEPARTMENT OF CHEMISTRY, NEWY O R K
RECEIVED DECEWEB 30, 1936
UNlVERSITY]
The Ternary Systems KC10,-K,S04-Hz0 and NaC10,-NazS04-H,01 BY JOHN E. RICCIAND NICHOLAS S. YANICK
Introduction This study is part of a systematic investigation of ternary systems involving sodium and potassium chlorates, a series of systems of which several examples are already to be found in the literature. No double salts containing sodium chlorate have yet been reported, the only ternary systems studied being NaC1O8-Na.COa-H20, NaC103NaC1-H20 and NaC103-KC10s-H20.2 Similarly, in the systems involving potassium chlorate that have been investigated, no compounds are found (-H20 KCI, K2C03, NaC10$; also +KBr and K13); potassium chlorate however is found to form solid solutions in the systems RC103-KN03-HzO a d RC10~-TlClO~-H~O, As for the sulfates in the present systems, while sodium sulfate is known to form both vari-
+
(1) Presented at the Pittsburgh meeting of the American Chemical Society, September, 1936. (2) "International Critical Tables," Vol IV, 1928. (3) Author's unpril,lished data.
ous double compounds and solid solutions .with other sodium salts, potassium sulfate, in systems so far studied, forms no double salts with other potassium salts, but does form solid solutions with potassium chromate and potassium molybdate.2 In the present investigation potassium chlorate and potassium sulfate show no complex formation, while the sodium salt system forms one double salt, NaC103.3Na2S04. As for the other sodium halogenates, sodium sulfate forms similar compounds with sodium iodate, namely, NaI03.3Na2SO1 and Na101.4NazS04,4 while with sodium bromate it forms no definite compound but a solid solution
Experimental Methods The experimental procedure was that usually described for similar investigations. Weighed complexes of known composition were brought to equilibrium by stirring in a (4) Foote and Vance, A m . J . Sci., le, 203 (1930) ( 5 ) Ricci, Tms JOWRNAL, 67, 805 (1935).
492
JOHN
E. RICCI.4ND
NICHOLAS
large water-bath in which the temperature was maintained The time required for attainment of constant to *0.02’. equilibrium was determined by analysis, and varied from a few days in the case of the potassium salts, to several weeks in some cases of the sodium salt system. The order of mixing of the components, and the process of “seeding” or inoculation for required phases, had to be varied in accordance with the phase sought. All the solid phases involving sodium sulfate show a considerable tendency to persist in metastable equilibrium, and these metastable phases sometimes change only very slowly to the stable form even with repeated seeding. The densities reported for some of the isotherms were obtained by means of volumetric pipets calibrated for delivery. The method of analysis of the saturated solution was the same in both systems. In one sample of the solution the chlorate was determined by a volumetric method; in another sample the total solid was determined by evaporation to dryness a t 100”followed by 250’; and the sulfate was then calculated by difference. For the chlorate determination, the method of Peters and Deutschliindere was used: to the chlorate sample (containing about 0.11 g. of CIOs-) is added a definite volume (50 cc.) of 0.05 M arsenious oxide solution (previously standardized against pure sodium chlorate by the same procedure); after the addition of a trace of potassium bromide, the solution is acidified strongly with hydrochloric acid and boiled for ten minutes. The excess arsenious oxide is then titrated by Gyory’s method,’ by means of 0.033 M potassium bromate solution (previously compared with the arsenite solution) using indigo sulfonic acid as indicator.
HsO
s. Y A N I C K
Vol. 59
crystals was not successful; the salt is always incongruently soluble; the crystals were very small, always contaminated with a mother liquor highly concentrated with respect to sodium chlorate, and readily decomposed by washing; even centrifuged residues contained large amounts of mother liquor or of its crystallized salts. Dehydration of residues over various drying agents showed no break in the drying-time curve, so that the solid appeared to be anhydrous. This however is also very clearly seen from the definite convergence of all the tie-lines for complexes giving the double salt as single solid phase, on a point on the NaCIO~-NanSOcside of the triangle. Considering the wide spread of the solubility curve of the double compound a t the various temperatures employed, and the fact that the compound is anhydrous, these extrapolations constitute a sufficiently accurate determination of the formula of the double salt. Extrapolating 38 such tie-lines, covering the three different temperatures a t which the double salt was obtained, to the point on the base of the triangle representing the formula NaC1O8.3Na2SO4 (containing 80.01% Na2S0a), the average absolute error of the extrapolations was 0.63% and the average algebraic error only +0.06%, in sodium sulfate. A further check on the formula was made by means of a method due to Bijlert;* two different complexes, of definite compositions, calculated to give the double salt (in metastable equilibrium) were made up, with the addition of a definite amount of a fourth component, sodium chloride, to each. By means of a complete analysis, when equilibrium had been reached, both of the saturated solution and of a wet residue, the amount of mother liquor contained in the wet residue was calculated through the sodium chloride content, thus making possible quite an accurate determination of the composition of the double salt. The results again gave an anhydrous compound, with 80.45 and 80.24% NanSOnin the two different runs, as compared with 80.01% calculated from the formula NaC10s.3Na2S0,.
Results System KC103-K&O~-H~O.-The results on this system are given in Table I, and the curves for the three temperatures are shown in condensed form in Fig. 1. No complex formation is observed, the only solid phases being potassium chlorate and potassium sulfate. System NaClO~-Na$30~-H~O.-The experimental data for the four temperatures studied (75,45,25 and 1 5 O ) are presented in Tables 11-V, the isotherms being shown graphically in Figs. KC108 &so4 2-5. (In these tables, the abbreviation “D.S.” stands for “double salt,” while (m) indicates Fig. 1.-System KC10~-K&04-H~0. metastable phases.) For the identiiication of known solid phases, microscopic 75’ Isotherm.-The solid phases a t this temexamination and algebraic extrapolation of tie-lines suf- perature are NazSOs for the curve a-b, NaC10y ficed. The determination of the formula of the new double 3NaS04 for b-c, and NaC103for c-d. As may be salt however was more difficult. Direct analysis of the seen from the diagram, the double salt exists as a (6) Peters and Deutschlinder, A p o f h . Z., 594 (1926); see Rolthoff stable phase over a short range of variation of and Furman, “Volumetric Analysis,” Vol. 11, John Wiley and Sons, N e w York, N. Y., 1929, p. 465. (7) Gy(iry, 2.a n d . Chem., 31, 415 (1893).
(8) Bijlert, 2. physik. Chem., 8, 343 (1891); see also Bancroft, J . Phur. Cibm., 6,178 (1902).
THETEKR'AKY SYSTEMS KC10~-K&OrH~O AND NaC103-NaaS04-HZO
March, 1937
TABLE I KClOs-KtSO4-HzO Original complex, wt. % KClOs KzSOd
0.00 ... 12.23 19.51 21.04 7.99 Av. (of 2) ... 0.00
...
0.00 1.60 2.89 4.95 10.03 16.03 Av. (of 16.51 18.04 20.06
20.02 20.42 19.80 14.01 9.11 3) 7.20 4.85 2.35
...
0.00
0.00 ... 3.51 20.02 18.01 7.01 Av. (of 2)
...
0.00
Satd. s o h ,
z&oc 45 O 0.00 13.53 9.80 9.13 9.80 9.12 9.80 9.13 13.90 ...
KCIO?'
Density
Solid phnse
0.00 1.80 3.30 4.96 4.96 4.96 4.96 5.06 5.77 6.72 7.8917
25' 10.76 9.93 9.43 8.66 8.62 8.62 8.64 8.19 5.57 2.73 0.00
1.083 1.089 1.099 1.102 1.100 1.099 1.100 1.099 1.080 1.063 1.048
0.00 3.29 3.29 3.29 5.676
15 9.258 7.86 7.86 7.86 0.00
1.076 1.085 1.084 1.085 1.032
0.00 5.00 23.98 33.07 42.22 46.11 44.98 50.91 51.71 52.11 52.98 53.08 Av. (of 55.14 39.76 40.68 44.98 47.80 48.88 50.73 51.09 53.49 54.17 54.99 56.63 56.83 58.13
... 39.96 21.10 11.98 10.06 10.03 14.99 6.88 7.02 8.06 6.89 7.04 3) 6.09 10.88 12.01 8.44 7.92 7.97 6.95 6.98 5.02 6.11 6.02 5.00 6.89 5.00
0.00
61.40
...
0.00 15.09 25.59 33.22 34.62 35.01 41.76 45.12 46.14 44.15 Av. (of 49.05 20.18 27.78 32.94 36.96 39.03 KzSOc+KClO, KzSOA+KClOs KzSOi+KClOa KC108
Satd. soln.. wt.
60.56 60.80 60.73
1.05 0.93 1.00 0.00
D.S. D.S. D.S.
%
NaClOs NaSSOd
Solid phase
0.00 30.33 6.26 24.70 27.19 10.56 35.05 6.88 45.51 3.19 50.00 2.39 51.85 2.09 53.63 1.92 54.59 1.73 55.78 1.57 55.62 1.51 55.74 1.49 55.71 1.52 57.81 1.61 41.42 5.11 42.98 4.50 46.82 3.27 49.91 2.51 51.15 2.28 52.84 1.94 53.20 1.99 54.90 1.84 56.25 1.62 57.26 1.30 58.34 1.37 59.79 1.05 60.10 1.14
NatSO4 N~zSOI NazSOt N~zSOI Na2SO4 Na2SO4 NazS04 NazSO4 NazS04 NazSO4 D.S. NazSO, D.S. Na2S04 D.S. Na90, D.S NazSOd (m)
+
+ + +
'
D.S. (m) D.S (m) D.S. (m) D.S. (m) D.S.(m) D.S.( m ) D.S.(m) D.S. (m) D.S. D.S. D.S. D.S.
D.S.
42.14 44.99 47.03 47.17 48.59 49.13 49.83 55.32 60.95 Av. (of
...
...
0.00 17.88 31.36 36.12 37.97 41.84 45.88 48.64 49.76 49.66 49.71 51.46 20.10 28.23 33.73 37.67 40.14 43.56 46.18 49.48 50.22 51.79 52.57 53.16 53.02 53.12 53.10 54.59
30.07 25.60 14.33 14.28 20.05 12.20 10.03 10.07 15.05 2) 7.01 21.28 15.92 13.03 10.04 10.04 9.01 6.98 8.95 10.04 10.06 10.04 9.97 6.06 2.11 5) 0.00
+ NaClOa + NaClO, + NaClOs
NaClOa TABLE I11 NaC10rNazS04-H20AT 45
Original complex, Satd. soln., wt. % wt. 01 NaClOa NarSO4 NaClO: daaSO4
TABLE I1 NaCIOrNazSOd-HIO AT 75 O Original complex, wt. % NaClOl NarSO4
6.89 3.01 Av. (of 4)
59.30 62.19
493
32.08 17.52 9.03 6.87 6.09 4.61 3.55 2.80 2.53 2.60 2.57 2.38 18.68 12.66 9.13 7.00 5.85 4.45 3.57 2.67 2.40 2.21 1.97 1.80 1.85 1.70 1.77 0.00
Solid phase
Na~S04 NazSO4 NazS04 NazSOd NaZSO, NazS04 NazSO4 NaZSOd N~zSOI D.S. NazS04 D.S NazS04 D.S. NazSO4 (m) D.S. ( m ) D.S. (m) D.S. (m) D.S. (m) D.S. (m) D.S. (m) D.S. (m) D.S. (m) D.S. D.S. D.S. D.S. NaCIOI D.S. NaC103 D.S. NaC103 D.S. NaC103 NaC108
+ + +
+ + + +
TABLE IV NaC1Ox-NazSO4-Hz0AT 25' Original complex,
wt. %
NaCIO: NapSO,
0.00 5.13 10.04 15.09 20.98 25.94 27.50 27.37
...
Satd. soln., wt. % NaClOI NarSOd
24.11 21.02 18.99 15.99 13.76 14.00
0.00 6.58 12.30 18.05 23.45 27.36 28.92
21.78 18.20 15.77 13.90 12.64 12.06 12.21
14.74
28.87
12.03
Av. (of 2)
28.90 12.12
22.80 19.32 26.32 15.50 27.46 15.52
29.29 29.52 29.90
12.23 12.20 12.25
26.30
29.89
12.27
29.90
12.26
0.00
33.97
18.34
Av. (of 2)
0.00
...
Solid phase
NazS04.10HzO NazS04.10H20 Na2S04.10HzO NazSOd.1OHzO Na~S04.10H~O N~~SOCIOHZO NazSO~.lOHzO NazSO4 NazSOd.10HzO NazSO4 NaZSOc10HzO NaBOt Na~SO4-10H~0 (m) NazS04*10H20 (m) NazSOd.10HzO (m) D.S. (m) NazS04.lOHzO (m) D.S. (m) NazS04.10HzO (m) D.S. (m) NarS01(rn)
+ + +
+ + +
491
JOHN
TABLE IV
(Concluded)
Original complex,
Satd. soln.,
NoClOa NasSO4
NaCIO, NaaSOc
5.06 40.13 14.92 30.09 26.99 15.96 29.20 18.89 34.89 15.02 38.04 15.05 69.91 15.01 44.56 8.07 45.84 5.06 46.01 5.02 Av. (of 3) 25.00 19.02 26.83 16.94 30.30 15.19 31.07 15.04 31.92 15.09 33.19 13.48 33.49 14.05 35.00 13.08 36.07 13.06 39.10 9 . 0 5 39.80 11.04 43.03 8.06 42.49 11.03 45.03 14.98 46.98 5.50 53.24 4.03 Av. (of 7) 48.67 4.55
6.03 17.09 28.02 32.47 38.07 42.39 44.76 46.28 46.26 46.40 46.31 25.26 27.00 30.80 31.65 32.71 33.85 34.36 36.08 37.31 39.75 41.19 44.10 44.55 46.57 46.63 46.68 46.62 46.63
28.fi2 19.89
48.46
46.64
3.85
Av. (of 2)
46.64
3.86
54.99
47.62 50.14
2.80 0.00
e. %
,
..
6.20
2.40 0.00
wt.
E. l
