When anhydrous, cobalt(II) bromide appears as green crystals. The hexahydrate loses four waters of crystallization molecules at 100°C forming the dihydrate:CoBr2.6H2O → CoBr2.2H2O + 4H2O
Further heating to 130°C Produces the anhydrous form:CoBr2.4H2O → CoBr2
The anhydrous form will then melts at 678°C. At higher temperatures, cobalt(II) bromide reacts with oxygen, forming cobalt(II,III) oxide and bromine vapor.