GUNNAR 0. ASSARSSON AND AINOBALDER
416
Vol. 58
EQUILIBRIA BETWEEN 18 AND 100' IN THE AQUEOUS TERNARY SYSTEM CONTAINING Sr2+,Mg2 AND C1+
BY GUNNAR0. ASSARSSON AND AINOBALDER Chemical Laboratory of the Geological Survey of Sweden, Stockholm 60, Sweden Received January 8, 1964
The ternary system strontium chloride-magnesium chloride-water has been investigated between 18 and 100". No double salt occurs within this temperature range. The 12west formation temperature of strontium chloride dihydrate is a t 19.4', that of strontium chloride monohydrate is at 80.5
Downloaded by UNIV OF CALIFORNIA SANTA BARBARA on September 7, 2015 | http://pubs.acs.org Publication Date: May 1, 1954 | doi: 10.1021/j150515a008
.
In two earlier papers the present authors' reported the results from the investigations on the equilibria in the system calcium chloride-strontium chloride-water and this system combined with potassium and sodium chlorides. As these components also occur together with magnesium chloride, there are good reasons for extending the investigations to include this component. Earlier Royer2 assumed the occurrence of a double salt between strontium and magnesium chlorides with composition similar to that of tachydrite. This assumption was based upon the ebullioscopical properties of the solutions a t 100". Recently Dodonov, Eferova and Kolosova3 evaporated samples from some brines in the Saratovsk oil district a t about 30". They obtained the compounds tachydrite, carnallite and 2CaClz. MgC12.6H20. Moreover, they assumed the presence of double salts of hydrates of calcium and strontium chloride, but no compound containing strontium and magnesium chloride. The supposed double salts might have been the solid solution of the hexahydrates of calcium and strontium chloride, described by the present authors.' It seemed therefore to be necessary to investigate the 40
A
aqueous system of magnesium and strontium chloride more systematically. Experimental.-The experiments were performed as earlier described.' Magnesium and strontium were determined in the solutions and the solids in the following manner. The weighed sample, contained in a platinum crucible, was transformed into sulfates and weighed. From the mixed sulfates magnesium sulfate was extracted by a solution containing 50 vol. water, 50 vol. ethyl alcohol and 1 vol. sulfuric acid. The strontium sulfate was filtered off, washed with the extraction solution and with pure ethyl alcohol, ignited gently and weighed. The magnesium chloride content was calculated by difference. The analyses of solutions of known composition showed an agreement within 0.2-0.470 between the found and calculated values for the total weight of chlorides present.
Results.-The results will be given briefly here. There is no double salt in the system between 18 and 100". It is noteworthy, that the saturated magnesium chloride solutions contain only small amounts of strontium chloride and that they have a very strong dehydrating influence on the strontium chloride hydrates, similar to that of the corresponding calcium chloride solutions' (Table I). No isotherms will be given here. A synopsis of isothermally invariant equilibria is given in Fig. 1. There it is presumed, that the solubility of strontium chloride in the magnesium chloride solutions is insignificant below 0". At higher temperatures the anhydrous chlorides of the two components form melts; the composition a t their eutectic point a t 535" is 62% strontium chloride and 38% magnesium ~ h l o r i d e . ~ TABLE I THETERNARY SYSTEM S R C L ~ - M G C ~ - H ~SOME O ; EQUILIBRIA BETWEEN
Temp., "C.
/
\
18 AND 100"
Wet residue MgCli SrCIr
18.9 19.4
1.2 1.3
34.8 34.7
36.2 33.8
19.9 80 81 100
1.3 1.7 1.7 1.7 1.5
34.8 39.0 39.2 41.2 42.0
57.5 51.4 36.4 57.2 0.6
Fie. 1.-Synopsis of the composition of the solutions at the invariant and univariant equilibria of the ternary system SrCI2-MgCl2-H2O. (1) C.0. Assarsson a n d A. Balder, THIS JOURNAL, 51, 717 (1953);
Solution MgClr SrClr
Solid phase
15.3 SrC12*6H20 16.6 SrC12.6H20 SrC12.2Hz0 10.5 ,SrCl2.2H~0 15.3 SrC12.2H20 23.8 SrCla*HnO 15.6 SrCIrH20 45.5 MgCla.6HaO
+
THEINVARIANT POINTS
68, 253 (1954).
19.4 f 0 . 2
(2) E . Royer. A n n . chim. [IO] 13, 451 (1930). (3) Y. Y. Dodonov, L. V. Eferova and V. S. Kolosova, Doklady Akad. Nauk. S.S.S.R., 63, 301 (1948).
80.5 rt 0 . 5
SrCh
Solution MgClr
1.3 1.7
34.7 39.1
SrC12.6H20 SrCI2.2H20
+ SrC12.2H20 + SrCI2.H20
(4) C. Sandonnini, Gazz. chim. itaZ., 44, I , 343 (1914).
.
