Stannous Bromide, SnBr₂

Stannous Bromide, SnBr₂, is prepared by allowing molten tin to cool to 200° C., powdering the metal in a mortar, and dissolving the powder in concentrated hydrobromic acid solution. It may also be obtained by heating tin in hydrogen bromide gas, or distilling the metal with mercuric bromide. It is a pale yellow, crystalline mass, of density 5.1, which melts at 215.5° C., and boils at 619° C. The heat of formation of the solid from tin and liquid bromine is 61,500 calories. Stannous bromide forms a hydrate with water, which is probably SnBr₂.H₂O; it is, however, hydrolysed by much water, with separation of a white oxybromide. With ammonium bromide, stannous bromide forms the complex salt (NH₄)₂SnBr₄.H₂O or (NH₄)₂SnBr₄.2H₂O, and also, NH₄SnBr₃.H₂O; whilst with ammonium chloride (NH₄)₂SnBr₂Cl₂.H₂O and with potassium bromide K₂SnBr₄.2H₂O and KSnBr₃.H₂O result.