of the Cacodyl Series. 389 



No. 3. Third Distillation. 



Substance 0-5930 



Carbonic acid 0'4265 



Water 0-2635 



Tube before burning .... 83-0195 



... after burning 82-3270. 



These results (a repetition of which, I think, unnecessary, 

 as the weighing of the tube after burning serves as a check 

 upon them) give the following compositions: — 



1st distillation, 2nd distillation, 3rd distillation, 



at 90° to 100° C. at 100° to 170° C. at 1 70° to 200° C. 



equiv. equiv. equiv. 



Carbon. . . 4. 28-95 4- 26'31 4 19-88 



Hydrogen . 6-1 7*26 6-05 6-46 6-1 4-82 



Arsenic. . . 1-3 64-31 1'7 67*15 2-55 75*50 



100-52 99-92 100-23. 



It follows from the analysis, that this radical, on distillation 

 with chloride of zinc, undergoes a catalytic decomposition 

 without the separation of arsenic, dividing into two or more 

 compounds, in which the same quantity of carbon is combined 

 with different quantities of arsenic; a circumstance of much 

 interest as regards the theory of organic radicals. It is there- 

 fore probable that cacodyl, like arsenic, is a binary radical 

 composed of C4 Hg, and that its constituent elements are com- 

 bined in such a manner that the compound of the cacodyl series 

 are repeated in a similar way, only of a higher order. The 

 above-described products of decomposition undergo, at a tem- 

 perature of about 400"^ to 500° C, a decomposition, which I am 

 in hopes, from the peculiarities in the constitution of the radi- 

 cal, to direct attention to. When cacodyl, or the before-men- 

 tioned mixture of the product of decomposition, is heated in a 

 bent retort over mercury, the gas of this substance is decom- 

 posed, at a temperature little exceeding the boiling point of mer- 

 cury, into metallic arsenic and a mixture of a compound of car- 

 bon andhydrogen, withoutthe separation of a particleof carbon. 



This gaseous substance burns with a variegated light flame, 

 with a very slight deposition on glass of metallic arsenic. A 

 solution of sulphate of copper, or nitrate of mercury, has no 

 action upon the gas, however long it may remain in contact. 

 With chlorine over water it takes fire, like a mixtui'e of phos- 

 phuretted hydrogen, and burns with deposition of carbon, 

 producing a red-coloured flame. Mixed with oxygen gas and 

 inflamed by the electrical spark, it explodes more powerfully 

 than fulminating gas, and generally breaks the vessel. Eudio- 

 metrical examination of the gas gives the following results : — 



