The solubility of mercury in water has been determined between 4 and 72 "C. Standard thermodynamic functions have been evaluated for mercury transfer from the liquid metal to aqueous solution and from aqueous solution to the gas phase. Mercury in water exhibits large positive deviations from Raoult's Law and shows a high relative volatility of 15 400 at 25 "C.La solubi!ite du mercure dans I'eau a ete determinee entre 4 et 72 "C. Les fonctions thermodynamiques standards ont et6 evaluCes pour le pasage du mercure du metal liquide a la solution aqueuse et de la solution aqueuse a la phase gazeuse. Dans l'eau, le mercure montre une deviation positive importante par rapport a la Loi de Raoult et une volatilite relative importante de 15 400 a 25 "C.

The electrochemistry of the ions of zinc, cadmium, and mercury in the A1C13-NaCI-KC1 eutectic at 150 "C was investigated by e.m.f., voltammetric, and chronopotentiometric techniques. Oxidation states of +2 were observed for these three elements and oxidation states of +1 were observed for cadmium and mercury. Values of equilibrium constants for the reactions Cd2+ + CdO F? Cd22+ and Hg2+ + HgO Hg22+ were calculated to be 26 and 36 000 respectively. A standard potential scale for the Zn(II)/Zn, Hg(II)/Hg(I), Hg(I)/Hg(O), Ag(l)/Ag(O), and Al(III)/Al(O) couples was established in the solvent system A1C13-NaC1-KC1.

The solubility of gypsum and anhydrite have been determined at 65 "C in aqueous 3.0 to 6.1 m NaCl solutions. Gypsum solubility at 30 "C has been determined in 5.9 m NaCl and in saturated sodium chloride. At 65 "C gypsum reacts with sodium chloride solutions more concentrated than 3.7 tn NaCl to form disodium pentacalcium sulfate, Na2Ca,(S04)a.3H20, which is isomorphous with calcium sulfate hemihydrate. The solubility of this double salt has been determined at 65 "C in aqueous 4.0 to 6.3 m NaCl solutions.Canadian Journal of Chemistry, 48, 3733 (1970) Introduction5CaS04.3H20, which was shown to be petro~l t h~~~h many phase equilibrium studies have graphically identical with that found by Hill and been made of the geologically important CaS04-Wills (9) in the CaS04-Na2S04-H20 system. NaC1-H2O system, the relative solubilities of Without X-ray analysis Marshall and Slusher (1) gypsum, hemihydrate, and anhydrite in concen-Were unaware that the solid disodium pentatrated sodium chloride brines are uncertain at calcium sulfate was isomor~hous with the 65 OC. ~1 1 recent solubility measurements in sodium-containing calcium sulfate hemihydrate concentrated sodium chloride solutions have reported to be non-stoichiometric by Powell (8). been made (1-5) by determining the saturation TO better define the CaSO4-NaCl-HzO system calcium ion concentration and assuming an equal at 65 OC, we have determined the solubilities of concentration for the dissolved sulfate ion. gypsum and anhydrite and for the first time have Arguments for this equality have been given by measured the solubility of the double salt PreZen (2). While this assumption may be true for pared in situ with a range of concentrated sodium gypsum solubility in concentrated brines at chloride solutions at 65 "C. The uncertainty of ambient temperatures, the equivalence of calcium the formula and structure of the double salt and sulfate is contrary to observation above f~r m e d from the reaction of gypsum with con--65 OC, where the sulfate ion levels are shown to centrated sodium chloride brines at higher tembe significantly lower than those for calcium (6) ; peratures has been unequivocall~ resolved by our this early work provides the first evidence for the identification of disodium pentacalcium sulfate reaction of gypsum with concentrated sodium by chemical, X-ray, and differential thermal chloride brines to form a double salt.analyses. Eipeltauer (7) and Powell (8) described the Experimental reaction of gypsum with concentrated brine at

Bromine chloride hydrate, prepared free of excess halogen, has been analyzed directly to give the formula BrC1.7.77 _+ 1.58 H20. The halogen is found to be bromine-rich in the hydrate and brominedeficient in the aqueous solution at 5 OC. Aqueous solutions in equilibrium with the hydrate between 1 and 15 "C have been analyzed and yield the bromine chloride.hydrate enthalpy of fusion 10 450 _t 860 cal/mole which leads to the formula BrCI.7.28 k 0.60 HzO. It i s concluded that bromine chloride forms a normal clathrate-type gas hydrate of forn~ula BrCl.7.34 H20, and that the frequently quoted formula BrCL.4 HzO is wrong.

The solubility of mercury in aqueous 6.10 m NaCl has been determined between 5 and 70 °C. Solubility equations and thermodynamic functions are derived and compared with those for mercury in water. Salting-out constants are given.