800 CACODYL. 



succeeded also in isolating cacodyl, the supposed radical of the 

 series, a discovery of much interest for the theory of compound 

 radicals. 



CACODYL. 



Formula C 4 H 6 As = Kd. 



Cacodyl is a liquid obtained from the continued digestion of 

 the chloride of cacodyl with metallic zinc at 230, and dissolving 

 out the chloride of zinc formed by water. It is dried by quick- 

 lime, distilled in a glass retort filled with carbonic acid to 

 exclude air and crystallized repeatedly at 21.2 (6 centig.) 



Cacodyl is an ethereal limpid liquid (greatly resembling its 

 oxide), of a nauseous odour, which crystallizes in shining prisms 

 at 23. It takes fire spontaneously in air and in chlorine gas, 

 with the formation of a cloud of white smoke. It sinks in water, 

 in which liquid it is insoluble ; it is soluble in alcohol and ether. 

 Its boiling point is about 338 (1 70 cent.); the density of its 

 vapour by experiment 7101? by theory 7281 ; its combining 

 measure 2 volumes. Its vapour is decomposed at a red heat 

 into arsenic, olefiant gas and light carburetted hydrogen. 



Oxide of cacodyl, alcarsin, C 4 H 6 As4-O = Kd O. Is pre- 

 pared by the distillation of a mixture of equal weights of dry 

 acetate of potash "and arsenious acid. At the same time metal- 

 lic arsenic distils over, with acetic acid and acetone which 

 float in the receiver above the fluid alcarsin. The latter is ob- 

 tained pure by washing with water free from air, and by distil- 

 lation from quicklime in a retort filled with hydrogen gas, and 

 from which atmospheric air is most carefully excluded. Oxide 

 of cacodyl is also produced by the direct oxidation of cacodyl 

 from slow access of air; and also from the partial reduction of 

 cacodylic acid by phosphorous acid. 



Oxide of cacodyl is an ethereal limpid liquid, of very consi- 

 derable refracting power, 1.762; it boils at about 302 (150 

 cent.), and solidifies in the form of white silky plates at 9.4 

 ( 23 cent.) Its odour suggests that of arsenietted hydrogen, 

 is most disgusting, and provokes a copious flow of tears. The 

 density of its vapour is 7555 by experiment, and 7833 by theo- 

 ry; its combining measure 2 volumes. It takes fire sponta- 

 neously in air and burns with a white flame and strong odour. 

 Taken internally alcarsin is a violent poison. 



