ON THE PROTO-IODIDE OF IRON, &C, 
115 
AH the characters, whether physical or chemical, demon- 
strate that the iodide of Pharmacy is not a proto-iodide of 
iron; 
1. This salt, instead of being without color, or very slightly 
greenish, as the proto-iodide should be, is always a brown of 
greater or less depth; 
2. When dissolved in water, the liquid which should be 
without color is of a reddish brown, more or less deep, ac- 
cording as the iodide has been subjected for a greater or less 
time to the influence of atmospheric oxygen ; 
3. The odor and taste of this solution evidently indicate 
the presence of a notable quantity of free iodine; the solution 
of proto-iodide recently prepared, and pure, is inodorous, and 
has no other taste than that proper to all the ferruginous 
salts; 
4. The colorless solution of proto-iodide does not exercise 
any apparent action upon starch; a single drop of the solu- 
tion of the iodide of the Pharmacopoeias immediately strikes 
a blue color; 
5. If, after greatly dilating the solution of the solid iodide 
of the Pharmacopoeias, it is tested by the yellow cyanide of 
potassium and iron, it immediately becomes a deep blue. The 
solution of the proto-iodide of iron, on the contrary, when 
well prepared, that is to say, when perfectly colorless, and 
not subjected to the influence of atmospheric oxygen gives 
with the same, like all the protosalts of iron, a precipitate of 
a bluish white. 
To recapitulate, according to these characters, the solid 
iodide of Pharmacy, designated in the Pharmacopoeias, and 
the formulae under the name of proto-iodide of iron, should 
be considered as a mixture in variable proportions of— 
Free iodine, 
Periodide of iron, more or less mixed with proto-iodide, 
not yet decomposed, 
Sesquioxide of iron. 
The presence of free iodine, or at least of an iodide strongly 
