Mercury(II) bromide is a colorless solid. It is very toxic and similar to mercury(II) chloride. It can form explosive mixtures with potassium. It also reacts violently with indium at high temperatures. It is corrosive.
It is used as a reagent in a reaction in organic chemistry. It is also used to test for arsenic. The arsenic is reacted with hydrogen to make arsine, which reacts with mercury(II) bromide to turn it yellow or brown.