Dark red, almost black, oily liquid with an unpleasant odour; hygroscopic; rapidly liberates Br2 in air, simultaneously separating Se. Partially decomposed on heating; first, some Br2 escapes, then some SeBr4 sublimes, and between 225 and 230°C, a part of the Se2Br2 boils without decomposition, leaving a residue of Se. In water, Se2Br2 sinks to the bottom in oily drops and gradually decomposes into Se, SeO2 and HBr, soluble in CS2 and CHCl3.
A round-bottom flask, equipped with a separatory funnel and gas outlet tube connected to a P2O5 drying tube, is filled with a suspension of 20 g of pure powdered Se in 50 ml of dry CS2; 20 g of pure Br2 is then slowly added from the separatory funnel. If the flask is occasionally shaken, the reaction is soon complete. A reddish-brown solution is formed, from which the CS2 is evaporated in a vacuum as rapidly as possible. The product is deep-red, pure Se2Br2.
A round-bottom flask, equipped with a separatory funnel and gas outlet tube connected to a P2O5 drying tube, is filled with a suspension of 20 g. of pure powdered Se in 50 ml. of dry CS2; 20 g. of pure Br2 is then slowly added from the separatory funnel. If the flask is occasionally shaken, the reaction is soon complete. A reddish-brown solution is formed, from which the CS2 is evaporated in vacuum as rapidly as possible. The product is deep-red, pure Se2Br2 .
