290 BUNSEN ON THE CACODYL SERIES. 
Diluted nitric acid unites with it in the cold without decom- 
position, and forms a thick liquid ; concentrated or hot acid im- 
mediately produces oxidation, with the formation of alcargen. 
The sulphate of cacodyl can be procured in a crystallized state. 
It may be formed by digesting the oxide in concentrated sul- 
phuric acid. The liquid changes on cooling into a white mass, 
which consists of groups of small crystalline needles. These 
crystals can be purified by pressure between folds of bibulous 
paper: they have an acid reaction, and deliquesce on exposure 
to air. The odour arising from them is most odious. 
I did not consider it necessary to prosecute the examination 
of these salts, as they can possess no other interest than what 
arises from the fact of their existence. The precipitates, how- 
ever, which the nitrate of cacodyl produces in metallic solutions, 
are much more remarkable. My experiments to determine their 
nature have all failed, in consequence of their instability. What 
I have made out is confined to a few changes, but I must defer 
their prosecution to another opportunity. 
The oxide of cacodyl agrees perfectly with inorganic bases in 
its reactions with the hydrogen acids. Haloid salts and water 
are formed ; the latter is either separated, or more seldom remains 
combined. The affinity of oxygen for the oxide of cacody] is 
remarkably energetic. It not only combines directly, but expels 
other bodies from their combination with that oxide: oxide of 
mercury, oxide of silver, oxide of gold are reduced, and even 
arsenic acid and indigo undergo a deoxidation. The characters 
of the degree of oxidation which thereby results, is already known 
from the laws of the compounds of the inorganic kingdom. The 
electro-chemical character, in both cases, depends upon the 
number of the atoms of oxygen which combine with the radical. 
Besides alcargen (cacodylic acid), there appears to be an inter- 
mediate degree of oxidation, which reacts as a superoxide. In 
another paper I will return to this subject, as well as to the other 
corresponding compounds of cacodyl. 
In concluding these remarks I may perhaps observe, that this 
oxide of cacodyl is a remarkably delicate test for arsenious acid, 
and may be used in judicial investigations as a most simple and 
safe means of distinguishing between antimony and arsenic. — 
Boil the matter containing arsenic in Marsh’s apparatus with — 
some water containing air, till the whole is dissolved, and mix — 
the solution with a little potash and acetic acid. On evapora- — 
