94 
PHARMACEUTICAL NOTICES. 
of each iodide, and half a pint of water, it would be greatly- 
simplified, and could be made extemporaneously. The 
addition of hydriodic acid to the solution is unnecessary in 
this case, and its design in the formula of Donovan is 
doubtless to supply any deficiency due to loss of iodine in 
the operation. 
The following formula, closely resembling that of Dono- 
van in the proportions, avoids the fractions of a grain : 
Take of Sesqui-iodide of arsenic, 36' grs : 
" Bin iodide of mercury, 34 " 
" Distilled water, half a pint. 
Triturate the two iodides with half an ounce of the 
water until they combine and dissolve, and then add the 
rest of the water, and filter. 
The sesqui-iodide of arsenic is easily prepared. One 
part of metallic arsenic is reduced to an impalpable powder, 
intimately mixed with five parts of iodine by trituration, 
then introduced into a small flask or thin vial, and the mix- 
ture very gently heated until liquefaction occurs. The 
vessel should be nearly full, so as to prevent the formation 
of much iodine vapour, and enable the operator to bring 
the fused iodide in contact with all parts of it, and include 
any iodine that may have sublimed on the sides. If, on 
cooling, the contents of the vial assume a reddish yellow 
colour and crystallize on the sides of the vial, and no iodine 
odour is apparent, the operation is finished. The vessel is 
then fractured and the iodide removed. 
If the arsenic and iodine are pure and the process skil- 
fully conducted, nearly the whole of the arsenic is combined, 
and the compound is quite pure enough for making Dono- 
van's solution without sublimation. 
The metallic arsenic should be bright and lustrous, and 
the iodine crystallized and free from water. The ordinary 
cobalt or fly stone, which is metallic arsenic, is often pure 
enough for pharmaceutical use. 
