386 Professor Burisen on the Radical 



relative condensation which the compounds of this radical 

 present, exactly agree with those of inorganic or simple ra- 

 dicals. This circumstance has given a weight to the theory 

 of the compound radicals which the law of substitution could 

 not reach. But this, in connexion with the phaenomena of 

 substitutions, does not advance the idea of organic radicals be- 

 yond the limits of a hypothesis. The proof of their reality is 

 connected with thi-ee other conditions, viz. on their isolation, 

 on the direct formation of their compounds, and on the actual 

 agreement of the density of their simple elements with their 

 theoretical density. All these conditions are fulfilled in regard 

 to cacodyl : it may be isolated, it enters into direct combina- 

 tions, and it has the density required if the laws of condensa- 

 tion of the inorganic elements are valid for organic bodies, as 

 may be observed by the following statement: — 



Observed. Calculated. 



Cacodyl 4 vol.C + 12 vol. H + 2 vol. As= 2 vol. Kd 7-101 7-281 



Cacodvl oxide ... 2 vol. Kd + 1 vol. = 2 vol. Kd O 7-555 7-833 



Sulphuret Cacodyl 2 vol. Kd + 1 vol. S = 2 vol. Kd S 7-810 8-39 



Chloride Cacodvl . 1 vol. Kd + 1 vol. Cl= 2 vol. Kd CI 4-56 4-86 



Chloride Cacodvl . 3vol.KdCl+lvol.KdO = 4vol.3KdCl+KdO 5-46 5-30 



Cyanuret Cacodyl . I vol. Kd + 1 vol. Cy = 2 vol. Kd Cy 4-65 4-54. 



This radical possesses the following properties : — 

 It is a clear, thin, highly refracting liquid, very similar to 

 oxide of cacodyl ; it has the same smell but is more inflamma- 

 ble. A glass rod moistened with it immediately takes fire 

 when exposed to the air: its boiling point is about 170° C. 

 At — 6° C. it crystallizes in large square prisms ; if the sub- 

 stance is pure it becomes like ice. It burns in oxj'gen gas with 

 a pale blue flame, and forms water, carbonic and arsenic acids, 

 which rise in the form of a white smoke. If the air is not in 

 sufficient quantity for the combustion Ery trarsin is formed, and 

 a black stinking mass of arsenic remains. In chlorine it burns 

 with a clear flame and deposits carbon. Digested with hydro- 

 chloric acid and metallic tin it is converted with the appear- 

 ance of various products into erytrarsin. The same substance 

 is produced by the action of phosphorous acid, chloride 

 of tin, and other powerful reducing agents. Fuming sul- 

 phuric acid dissolves the radical without combining with it. 

 In the cold a quantity of sulphurous acid is evolved, and on 

 distillation it gives off a substance with an agreeable JEthereal 

 odour, which appears to be sulphate of aetherol. 



2. Formation of the Compounds of Cacodyl from their 



Radical. 



The relative condensation of the gaseous compounds of 



cacodyl and the transformations which they undergo, give 



a great degree of probability to the theory of organic ra- 



