A
2-l. round-bottomed flask, surrounded by an
ice-water bath and provided with a
stirrer, a
separatory funnel, and an
outlet tube, is set up in a good
hood. To the flask are added
500 g. (160 cc., 3.1 moles) of bromine and 50 cc. of water (Note
1). To the stirred mixture is added gradually a solution of
170 g. of sodium cyanide (3.5 moles) in 1.2 l. of warm water. The temperature of the reaction mixture is kept below 30°. When the reaction is complete (about two hours or less) the
cyanogen bromide is distilled from a
steam bath, using a
500-cc. flask (Note
2) as a
receiver. The distillate is warmed with about
100 g. of anhydrous calcium chloride, filtered, and again distilled, preferably with the distilling flask used as a receiving vessel connected directly to the flask from which the
cyanogen bromide is being distilled. The product boils at
60–62°. It is melted in the receiver (Note
3) (Hood) and poured into a
warm tared bottle. The yield of white crystalline solid (Note
4) melting at
49–51° is
239–280 g. (
73–85 per cent of the theoretical amount).