Arsenic Oxybromide, AsOBr

Arsenic Oxybromide (Arsenyl Bromide), AsOBr, maybe prepared by dissolving arsenious oxide in molten arsenic tribromide and distilling off excess of the latter; the remaining liquid separates into two layers, the upper one consisting of the oxybromide and the lower one a mixture of the oxybromide and excess of arsenious oxide. The oxybromide sets to a brown buttery mass on cooling. The hydrated form, 2AsOBr.3H₂O, may be obtained by evaporation over sulphuric acid of a solution of the tribromide in aqueous hydrobromic acid, or by the action of bromine on aqueous phenylarsinic acid. It is decomposed on heating, yielding arsenious oxide and the tribromide. If the solution in dilute aqueous hydrobromic acid is cooled, a compound of composition 2AsOBr.3As₂O₃.12H₂O is obtained.