Y-12 Plant, Union Carbide Nuclear Co., Oak Ridge, Tenn.
F O R SEVERAL problems under investigation it wasdesirable to have more information than is published on the solubilities of lithium chloride in water and in hydrochloric acid and of lithium thiocyanate in water.The polytherm of lithium chloride has been investigated in parts by several authors (1-10, 12-14, 16, 18-20). The existance of the monohydrate and the dihydrate and their temperature limits are well established. The existence of a trihydrate and of a pentahydrate was first proposed by Bogorodski (4) and Huttig and Steudemann (9), respectively. Transition points were found by Huttig by thermal analysis. But the thermal effects a t the transition points are only small, so that this method is not very accurate. Determinations of solubilities yield usually more accurate results. But data found in the literature are also conflicting a t very low temperatures. The eutectic point of the system LiCl-H20 was found by Huttig a t -80" C., by Voskrenskaya (20) a t -66O C., by Foster D. Snell (19) and the Department of Chemical Engineering of the University of Maryland (13) below -96" C., by Garrett and Woodlow (7) a t -73" C. with 28.85% LiC1, and finally by Moran (14) a t -75.9" C. and 25.2% LiC1. I t was therefore desirable to redetermine the system LiCl-H20.No values of the system LiCl-HC1-H20 were available. Very few scattered data are found in the literature on the system LiSCN-H20 (11,15).
EXPERIMENTALSystem LiCI-Hg0. The lithium chloride used in the following measurements had been purified by several recrystallizations from water, until it was free from sulfate and contained less than 0.001% of calcium plus barium.In nearly all cases the solubility was found by determining the temperature a t which the solid phase disappeared. A quantity of solution (about 15 cc.) was crystallized quickly by cooling to low temperature. Seeding with the proper hydrates was necessary, because otherwise the entire system turned into a highly viscous or even solid, glass-like mass, which could not be crystallized a t all. Very fine crystals were obtained. The temperature of the system was then raised slowly-approximately 1" per 15 minutes. This rate was sufficiently low to obtain reproducible values. In that part of the system, where ice exists as the solid phase, undercooling is less severe. But on the other hand, seeding the undercooled solution with ice had no apparent effect. In view of these conditions, the melting points of the ice and the temperatures of complete dissolutionof the salt could be found only with the temperature of the system increasing.For the analyses of lithium, chloride, and thiocyanate, the usual standard methods were used. Many points had to be determined on the solubility curves of the chloride and the thiocyanate because of the low temperature coefficient of the solubilities. The values found are listed in Table I. From comparative measurements it could be estimated that the temperature readings were correct within f0.25" C. for the medium and wi...
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