— re Sn, 
BUNSEN ON THE CACODYL SERIES. 317 
for oxygen as the oxide of cacody]l itself. It could not even be 
accomplished by pressing the substance between folds of blot- 
ting-paper covered with tinfoil, in the case of an hydraulic press 
which was surrounded with carbonic acid. It becomes heated 
by the oxidation on removing the paper out of the apparatus 
previous to immersing it in the water, and melts, when it is ab- 
sorbed by the paper. I have in vain endeavoured to obtain it in 
a state of purity fit for analysis, in consequence of its great 
affinity for oxygen. There can however be no doubt as to its 
composition, from its character and the mode of its formation. 
Besides the neutral and basic compounds, there is no other 
substance formed on distilling the oxide of cacodyl with hydri- 
odic acid. The substance in question therefore can only be 
composed of iodide and oxide of cacodyl and water, or hydri- 
odic acid. The latter cannot be true, for protiodide of cacodyl 
remains unaltered by digestion with hydriodic acid. But it is, 
on the contrary, very easy to form it by mixing the protiodide 
with the oxide. These two bodies are miscible in any proportion 
with each other without undergoing any alteration. The moment 
however that a drop of water is added, the whole becomes a mass 
of yellow crystals, which have ail the characters of the substance 
obtained by distilling the oxide with hydriodic acid, and which 
form the same large crystals when covered with a layer of water 
_ as we observe in the other case. And further, when we find 
that the same products are formed by oxidation in the air in 
both cases, there cannot be a doubt as to its composition. We 
cannot however assume that there is the same atomic relation 
among the constituents, which is also proved by the difference 
in the characters. 
It forms a crystalline mass of a yellow colour, which crystal- 
lizes from its solutions in fine transparent rhombic plates. It is 
only slightly soluble in water, but easily so in alcohol. It melts 
considerably below the boiling point of water, and can be di- 
stilled without decomposition. It emits thick white vapours in 
the air, becomes heated so as to melt, and sometimes inflames. 
It burns with a sooty flame with the emission of iodine vapour. 
If these compounds of organic oxides with haloid salts pos- 
sess some interest in supporting the view which might be 
suggested regarding the nature of organic compounds, it is of 
great importance to determine accurately the peculiarities by 
which these substances are distinguishable from the correspond- 
