9S 
ON THE IODIDES OP AKSENIC. 
From my notes made at the time I copy as follows: — "Re- 
duce the arsenic to a fine powder, put it into a suitable glass 
flask, and moisten it with a small portion of water, agitating 
it until it is completely wet; then add the residue of the wa- 
ter and the iodine. Digest, by slow heat, until ebullition ensues. 
Immediately after boiling, the solution changes from a dull 
grayish-black color, to a very light reddish hue, and the smell 
of iodine becomes extinct. Combination being thus insured, 
filter the solution while hot, and evaporate slowly in a porce- 
lain dish. At a certain degree of concentration, a metallic 
pellicle forms upon the surface, covering it entirely, which, 
when agitated with a glass rod, is precipitated, forming a 
semi-crystalline mass. This is the sesqu'iodide of arsenic, 
but not in a state of absolute purity. Continue the evapo- 
ration, and dry the mass, constantly agitating it with a glass 
rod, to prevent its splashing out of the dish, and its con- 
sequent loss. When dry, the crystals are to be put into a 
well adapted capsule, of platina, or Berlin porcelain, and 
fused." 
The fusion should be conducted with skill and rapidity. 
It is decidedly preferable to raise the heat at once, than to 
prolong the process by gradual degrees of augmentation, 
as the salt is not only readily vaporised, but decomposed, 
during fusion. When fusion is complete, the liquid salt 
should be instantly poured upon a marble slab and allowed 
to cool. 
During fusion, copious orange-colored vapors are gene- 
rated, which are abundantly irritating to the eyes and fauces; 
and I would suggest the greatest caution against their inha- 
lation. 
If the process has been skilfully conducted, the frac- 
tured mass will present, at its edges, a crystalline appear- 
ance, the structure of which is lamellated. Externally, it 
has a dull metallic lustre, of a brick red color, not un- 
like some specimens of deut-oxide of mercury of inferior 
quality. 
