66 ALIPHATIC FLUORINE COMPOUNDS completely and facilitates filtration. The aqueous layer is separated as completely as practicable, and the remainder is filtered with suction and air-dried on the filter. The filtrate separates into a layer of acetylene tetrabromide and a layer of water. The solid material is removed from the filter, placed in a bottle, covered with chloroform, vigorously shaken for twenty minutes, and then filtered by suction. Pure mercuric bromide is left on the filter. The filtrate is a chloroform solution containing from 75 to 100 cc. of acetylene tetrabromide. By distillation of the chloro-form it is possible to recover the acetylene tetrabromide. 1,2-Dibromofiuoroethane and l-Bromo-2,2-difluoroethane. By a procedure analogous to that just described, 1,2,2-tribromoethane was converted to the mono- and di-fluoro derivatives. The reaction temper-ature had to be lower for good results. At 0°, the yield of mixed products was 50%; at —20°, 60-65%. At higher temperatures the yield was only
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