Thallic bromide, TlBr₃

Thallic bromide, TlBr₃, is not known in the anhydrous state. It can be obtained in solution by the action of excess of bromine on thallous bromide suspended in water. When the solution is concentrated at 30° to 40° to a syrup, and then strongly cooled, very pale yellow crystals of the tetrahydrate, TlBr₃.4H₂O, are produced. Meyer has obtained the monohydrate, TlBr₃.H₂O, by concentrating the solution in vacuo at the ordinary temperature. The hydrates cannot be dehydrated without loss of bromine. They absorb one molecular proportion of hydrogen bromide or hydrogen chloride. Willm has described the addition-compound, TlBr₃.3NH₃.