IODIDE OF IRON BY DOUBLE DECOMPOSITION. 
171 
These points well established, it is with much confidence 
that I propose the therapeutic employment of the prot- 
iodide of iron, mixed with sulphate of potassa. It presents 
the incontestible advantage of being found in a dry state 
without any alteration. 
The following formula can serve for pharmaceutical pre- 
parations, having a base of iodide of iron : 
Sulphate of protoxide of iron, 3 parts. 
Iodide of potassium, - - - 4 " 
It is important to choose the sulphate of iron, in little 
almost colourless translucid crystals, which are constituted 
with seven equivalents of water of crystallization. The 
iodide of potassium ought also to be perfectly neutral and 
pure ; the least alkalinity of the iodide will be discovered by 
the sulphate of iron, which in this case is a good test. For 
to be certain of the purity of the materials, the mixture of 
the two salts well pulverised, dissolved in a small quantity of 
water, ought not to be troubled by oxide of iron, either green 
or yellow, as the first indicates the basic character of the 
iodide of potassium, and the second that the sulphate of iron 
was partly sesquioxidised. 
Pills of Proto-iodide of Iron. 
{&. Crystallized sulphate of iron, - - 24.7 grs. 
Iodide of potassium, - 32.4 " 
Gum tragacanth, - 4.6 " 
Sugar, 15.4 " 
Syrup and powder of marshmallow, q. s., for making 
36 pills. 
Each pill contains .8 of a grain of dry iodide, of iron, or 
1.09 of the hydrated salt, and .4 grain of sulphate of pot- 
assa. 
The sulphate of iron is at first reduced to very fine pow- 
der in an iron mortar, afterwards the iodide of potassium, 
and then triturate the mixture to facilitate the reaction of the 
