ArticLe XII. 
Researches on the Cacodyl Series. By Rup. BuNSEN *. 
IN the following researches I have examined some of the nu- 
merous products which arise from the decomposition of alcarsin. 
They are not only well worthy of attention from the peculiarity 
of their composition and characters, but also as members of a 
series of compounds equally unusual and extensive, and must 
possess a general interest in extending our knowledge of the laws 
which regulate organic combinations. 
The simple relation which exists among these members ap- 
pears as the direct expression of the facts observed, and leads us 
to a view of the constitution of this class of bodies, which is also 
supported by the characters of the inorganic elements, and which 
seems to exclude every other method of interpretation. 
When we survey this group of substances, we immediately 
recognize an unchangeable member whose composition may be 
represented by SUSE Le: 
Tre tae ie 
which, in respect of the relative number of its atoms (but only 
in this respect), answers to common alcohol, in which the atom 
of oxygen has been replaced by half an equivalent of arsenic. 
The constituent elements of this member are united by a powerful 
affinity to each other, and collectively taken act a part in all the 
phznomena which attend and characterize the decompesition of 
these bodies. They form in this combination a unit of a higher 
order, which we call an organic atom or radical, which assumes a 
rank among the combination of organic elements, as figures do in 
our numerical systems, being subject at the same time to the 
laws of the original units, by whose aggregation they have been 
formed. Asrespects organic chemistry, the unparalleled power 
of affinity with which this radical is endowed, the facility with 
which it can be transferred from one compound to another, the 
humerous proportions in which it combines with the metalloids, 
and, above all, the electro-chemical character of the compounds 
* Translated from the German MS, of the author by Thomas Richardson, 
Sq. 
; In this translation H, Cl, &c. represent the double atoms or single equiva- 
lents, as used by English chemists. As represents 470-04 arsenic, and Hg 
1265°82 mercury. 
VOL. III. PART X. U 
