Arsenic tribromide, AsBr3, is formed by the direct union of arsenic and bromine, and subsequent distillation from the excess of arsenic; it forms colourless deliquescent prisms which melt at 20 0 -25° C., and boil at 220° C. Water decomposes it, a small quantity of water leading to the formation of the oxybromide, AsOBr, whilst a large excess of water gives arsenious oxide, As4O6.
With a little water it forms arsenic oxychloride, AsOCl, and with excess of water it is completely decomposed into hydrochloric acid and white arsenic. It combines directly with ammonia to form a solid compound variously given as AsCl3.3NH3 or 2AsCl3.7NH3, or AsCl3.4NH3 Arsenic trifluoride, AsF3, is prepared by distilling white arsenic with fluorspar and sulphuric acid, or by heating arsenic tribromide with ammonium fluoride; it is a colourless liquid of specific gravity 2.73, boiling at 63° C; it fumes in air, and in contact with the skin produces painful wounds.
117) as a scarlet amorphous powder by deposition of solutions of phosphorus in the tri-iodide, tribromide or sulphide (P 4 S 3).
761), and also when a solution of phosphorus in the trichloride or tribromide is exposed to light.
Halogen Compounds.-Phosphorus trifluoride, PF 3, discovered by Davy, may be obtained mixed with the pentafluoride; by direct combination of its elements; from the tribromide and arsenic trifluoride (Maclvor); from the tribromide and zinc fluoride, and from dried copper phosphide and lead fluoride (H.