T H E SYSTEM: CuS04-Li2S04-H20 H. D. CROCKFORD AND MACD > I . WEBSTER
The aqueous systems obtained with cupric sulphate and sodium, potassium] or ammonium sulphate have been studied somewhat in detail. Caven and Johnston* have critically reviewed the prior work on the system CuSO4Na2SO4-H20and have themselves determined the oo, z jo, and 37.5OC isotherms. They fail to state that Foote? determined the 12°C isotherm. The double salt, CuS04-Na2S04-zH20 appears as a solid phase at temperatures above 16.7'C. The systems: CuS04-K2SO~-H20and CuSO1- (IYH4)2SOaH20, have been critically reviewed .by Caven and M i t ~ h e l l ,and ~ the 2 5 O , j IO, and 61°C isotherms determined. The double salt CuS04-M2SO4-6H20 appears as a solid phase at all temperatures between oo and 6r"C, the limits of the investigations. S~hreinemakers~ has determined the 3ooC isotherm for the system: CuS04-Li2SOa-Hz0.I n this paper are given the results of a study of the oo, z j", and 55' C isotherms.
Experimental Procedure A series of solutions were prepared from the pure salts, CuS04.gH20 and Li2SO4.H3O1 with an excess of one or the other as a solid phase. For the o°C isotherm the bottles were immersed in a container of finely-ground ice and water. This maintained a temperature of around o.z-.j°C. For the other two isotherms the bottles were immersed in a constant temperature bath accurate to * 0.05'. Equilibrium was established in approximately three dags. The copper was determined by electrolytic precipitation and the sulphate content was determined by precipitation with barium chloride. The lithium sulphate content was determined by difference. The precipitation of the sulphate ion as barium sulphate in the presence of the lithium ion has been criticized as inaccurate due to the tendency of the barium sulphate to occlude the lithium salt. However, we found that if the determination was carried out very carefully the error introduced was negligible. I t was not considered necessary to determine all solid phases and only those around the transition points were analyzed. The compositions of the solids were determined from the wet residues by means of tie lines. KO wet residues were analyzed in the case of the z j°C isotherm. 1he data obtained are expressed in weight percent. R. M . Caven and William Johnston: J. Chem Soc., 1927, 23 j8.
* H. W. Foote: J. I n d . Eng.
Chem., 11. 629 (1919).
R.M. Caven a n d T. C . Mitchell: J. Chem Soc., 125, 1428 ( 1 9 ~ 4 ) . F.A. H.Schreinemakers: Z. physik. Chem., 66,689 (1909).
H.D. CROCKFORD AND MAUD M. WEBSTER
2376
Results and Conclusions Table I gives the values obtained. These values are plotted in the diagram along with those of Schreinemakers.
TABLE I 0°C Isotherm Sample
Liquid Phase %Lipso,
5
14,22 11.4: 10.47 6.95 5.33
6 7
5.55 5.90
8
5.52
I 2
3 4
IO
2.49 1.14
I1
-
9
Sample
%CuSOd
I
18.50
14.54
3 4
1 2 .7 7
10.80 I O . 46
Solid
-
C'uS04.5HZO 17
1.99
1,
8.57 20.00
J,
7.78
43 . o o
C'uS04.5H20Li2SOI.H90
23.63 23.90 23.71 23 .90
j9
40.92
59.54 1.18
8,86 61.62
IO.
25.21
,, ,
1,
Li2S04.H20 f'
25.95 26.33
z j°C Liquid Phase %CuSOd %Li,S04
2
5
Wet Residue %LitSOa
%CuSOr
Isotherm Iiquid Phase %CuSOI %LirS04
Sample
-
6
7 .j 2 12.36 17.06 18.03
9.41 9.12 9 .oo 3.64
I
8 9
-
IO
20.07
22.03 21
.87
21.32 2.;
SO
;. j"C' Isotherm Wet Residue
T.inuid Phase Sample
%CUbUi
%1>125U,
I
26.90
-
2
24.45 23.08
3.36
3 4
IKij
1 2 . 79
5 6
1 6 .j 3 15.97
' 7 .2T 18.32
7
15.73 12.90 i .32 6.07
18 41 19.8;
8 9 IO I1
-
6 . 2 2
21
.i6
22.55
24.62
%7oCUbUi
%LI?SO.
Solid
.
COPPER SULPHATE-LITHIUM SULPHATE-WATER
2377
I t is seen that the solubility of each salt component is decreased with increasing concentration of the second salt component. I n the case of Na2S04, K2S04,and (NH4)2S04the opposite is true. There is no indication of compound formation as with the above-mentioned salts. I t is seen that the position of the transition point as determined by Schreinemakers a t 3ooC does not appear to fit properly with the transition points as determined in this work and that his data does not appear to fit particularly well on a straight line.
FIG.I
There has been much conflicting data published on the solubility of lithium sulphate in water. Friend,' determined the solubility over a rather wide range of temperature and as he points out in his article his values differ very much from those of certain other investigators, especially a t the lower temperatures. The results obtained in this work for the solubility of the pure lithium sulphate agree well with those obtained by Friend. summary The oo, 2 5 O , and gj°C isotherms have been determined for the system: CuS0,-Li2S04-H20. The data agree in a general way with those obtained by Schreinemaker a t 3ooC and show that the solubility of each salt is depressed by the presence of the other. No double salts are found at any of the temperatures studied, the solid phases being CuS04.gHz0and LizSOa.H20. Department of Chemistry, Unzuerstty of North Carolzna.
J. A. N. Friend: J. Chem. SOC., 1929, 2330
