PROTOIODTDE OF MERCURY. 
327 
lie mercury, and is always less active than when made by the 
first process, and moreover it is impossible to procure a pure 
protoiodide by this method as this salt is composed of one 
atom of each of the constituents. 
As to the second and third processes, any advantages they 
may offer are balanced by a serious drawback — the difficulty 
of obtaining the mercurial salts at a minimum of oxidation. 
It must be evident that this is an indispensable requisite, as 
otherwise, the protoiodide would be mixed with variable 
quantities of the deutoiodide, rendering the remedy far more 
powerful and perhaps fatally so. 
The following I believe to be the best: 
P. Pure Calomel, giij 3v. 
Dry Hydriodate of Potassa, gij 3iv. 
Pulverize the hydriodate in a glass mortar and add the 
Calomel, place the mixture in a porcelain capsule and pour 
over it ten or twelve ounces of boiling distilled water. After 
cooling, decant the fluid, collect the precipitate on a filter and 
wash with distilled water. Dry in the shade and keep in a 
glass stoppered bottle. 
The protoiodide thus prepared may sometimes contain a 
minute portion of mercury or of its proto-chloride, arising 
from the hygrometic state of the calomel and hydriodate at 
the time of weighing them, but the quantity of either is so 
small as to be of no moment. 
Bull. gen. de Therap. 
