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Thorium Bromide, ThBr4

Thorium Bromide, ThBr4, is prepared similarly to the chloride, i.e. by the union of its elements, by acting on a heated mixture of thoria and carbon with bromine vapour, and by brominating thorium carbide at high temperature (Moissan and Martinsen). It may also obtained conveniently by the method of Bourion, which is generally applicable to the preparation of anhydrous metallic bromides from their oxides. This method consists in the simultaneous action of sulphur chloride vapour and hydrogen bromide on the metallic oxide heated to a suitable temperature. Thus a white mass of ThBr4 is obtained when sulphur chloride vapour at 135° C., mixed with hydrogen bromide, is distilled on to heated thoria, whilst if the temperature is lowered to 125° C. ThOBr2 results.

Anhydrous thorium bromide forms on sublimation transparent colourless needles of density 5.62. It sublimes in vacuo at 600°-620° C. and boils at about 725° C. It is hygroscopic, and easily soluble in water and alcohol. From a solution of thorium hydroxide in aqueous hydrobromic acid the crystallohydrate ThBr4.10H2O was obtained by Jannaseh; other observers have described the hydrates ThBr4.8H2O and ThBr4.7H2O. According to Chauvenet the dodekahydrate ThBr4.12H2O is obtained in needles by evaporating at 100° C. a solution of thorium hydroxide in alcoholic hydrogen bromide, and this salt when dried in the air passes into ThBr4.10H2O, which in a vacuum becomes ThBr4.7H2O. The heats of solution of the anhydrous salt and the different hydrates are: ThBr4, 70,190 calories, ThBr.7H2O, 22,550 calories; ThBr4.10H2O, 9,840 calories; ThBr4.12H2O, 2,300 calories.

Thorium bromide forms with ammonia the compound ThBr4.3NH3, and with pyridine (C5H5N)2H2ThBr6.
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