BUNSEN ON THE CACODYL SERIES. 295 
The seleniet of cacodyl obtained as above is a perfectly trans- 
parent yellow liquid, possessing a peculiarly offensive and highly 
penetrating smell, which is somewhat similar to that of the sul- 
phuret, but more zthereal and aromatic. It is insoluble in 
water, but very soluble in ether and alcohol. It does not smoke 
in contact with the air, but in a short time absorbs oxygen and 
deposits colourless crystals. It is less volatile than any of the 
other cacodyl compounds, but may be distilled without de- 
composition. It deposits selenium and a ring of arsenic when 
conducted through a heated glass tube. It burnsin the air with 
a fine blue flame, and emits the penetrating odour of oxide of 
selenium. 
It reacts with metallic solutions in the same way as the in- 
organic metallic compounds of selenium ; a seleniet and oxide 
of cacody] in combination with the acid of the metal result. It 
causes a black precipitate with acetate of lead, nitrate of silver, 
&e. It produces a black precipitate of seleniet of mercury in a 
solution of corrosive sublimate ; but on adding a larger quantity 
it is changed into the white compound of oxide of cacodyl and 
chloride of mercury, which easily dissolves in boiling water, and 
on cooling forms silky crystalline plates. 
Kd Se ) Hg Se 
3 Hg Cl eal Kd O + 2 Hg Cl 
HO H Cl 
It is easily oxidized by nitric acid; and the same effect is pro- 
duced by concentrated sulphuric acid, when heated, with the for- 
mation of sulphurous acid, while a red powder of selenium is 
deposited. 
I did not consider it necessary to make any analysis of it, as 
there can be no doubt of its composition. 
B. Haloid Compounds of Cacodyl. 
4, Cyanuret of Cacodyl. 
I have thought it best to commence this division with the 
description of this beautiful but highly poisonous compound, 
on account of the extraordinary facility with which it crystallizes, 
and the ease with which it may be obtained perfectly pure. It 
may be prepared by distilling a mixture of concentrated prussic 
_ acid and oxide of cacodyl. This method of preparation is at- 
tended with great danger, and affords a product which is ren- 
