OXIDE OF CACODYL. 801 



Oxide of cacodyl is but slightly soluble in water, but dis- 

 solves in all proportions in alcohol and ether. It dissolves in 

 caustic potash colouring the latter brown ; dilute nitric acid dis- 

 solves it without disengagement of gas, but when heated decom- 

 position occurs. Oxide of cacodyl dissolves phosphorus, sul- 

 phur and iodine; the solution of the last is colourless and 

 deposits crystals, which disappear again when an excess of 

 iodine is added. It combines with the hydrate of sulphuric acid, 

 forming thin needles which have an acid reaction and are 

 deliquescent. Besides combining with acids, oxide of cacodyl 

 combines also with salts. When its solution in alcohol is 

 mixed with a solution of chloride of mercury, a white precipitate 

 falls, soluble in hot water and crystallizing from it, which is a 

 compound of 1 atom oxide of cacodyl, and 2 atoms chloride of 

 mercury. This compound is inodorous. It yields with hydro- 

 chloric acid, chloride of mercury and chloride of cacodyl. 

 Oxide of cacodyl forms a similar compound with bromide of 

 mercury. It reduces the salts of the suboxide and oxide of 

 mercury. . 



Cacodylic acid, alcargen, HO, C 4 H 6 As O 3 = HO + Kd O 3 . 

 Cacodyl and its oxide left under water to the slow action of 

 air, oxidate so as to become cacodylic acid. The hydrated 

 acid crystallizes in large colourless prisms, is inodorous, not 

 poisonous, fusible, soluble in water and in alcohol. It is 

 reduced to the state of chloride of cacodyl by chloride of zinc, 

 and to the state of oxide of cacodyl by phosphorus acid. 

 Alcargen has a feeble arid reaction ; it combines with the 

 alkalies, giving rise to compounds which have the aspect of gum 

 and are not obtain^* under regular forms. It dissolves in the 

 hydrate of sulphuric ac id without being modified ; is not attacked 

 by anhydr^s sulphuric acid, and is oxidated with difficulty by 

 nitrir <*cid and aqua regia. 



M. Bunsen adds one atom of oxygen to the formula for 

 alcargen, but Liebig has shewn that the formula as given above 

 is more in accordance with Bun sen's analysis of alcargen than 

 his own view. 



Sulphuret of cacodyl, C 4 H 6 As + S = Kd S, may be obtained 

 directly by uniting cacodyl with 1 atom of sulphur, or by the 

 distillation of chloride of cacodyl with sulphuret of potassium. 



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