172 10 DIDE OF IRON BY DOUBLE DECOMPOSITION. 
two salts ; then add the gum, the sugar, the syrup, and, if 
necessary, the powder of marshmallow.* 
To preserve these pills from the action of the air, it will 
be well to cover them with gelatin by the process of M. 
Garot. But this manipulation requires too much time to 
render it practicable for small quantities. 
A mass which is readily preserved, is obtained by re- 
placing the syrup and gum of the formula by 30 grains of 
crum of bread. 
The water of the bread liquifies remarkably the sugar 
and salt, the powder of marshmallow is added to give the 
mass the necessary consistence. The gluten and soluble 
amidon of the bread form a varnish, which, by hardening, 
circumscribes the action of the air to the surface of each 
pill. 
These pills are rolled in lycopodium and placed in a very 
dry place. 
The following preparations can replace those described 
in the formularies : 
Tincture of Proto-iodide of Iron. 
R. Sulphate of iron, S parts. 
Iodide of potassium, - - - 10.5 " 
Alcohol 36° Baume, - - 160 " 
The two salts are triturated, as before described, the proto- 
iodide of iron dissolved by means of the alcohol, and fil- 
tered. 
It is preserved in glass stoppered vials which should be 
exactly filled with the tincture. A slight excess of the 
iodide of potassium gives it more stability. 
This tincture contains about one part of iodide of iron in 
16 parts. 
* A formula for pills of iodide of iron by our colleague, Henry W. Wor- 
thington, was published in vol. 15th, p. 71, of this journal, in which he evapo. 
rates a concentrated solution of the ferruginous iodide made by the process 
of the Pharmacopoeia with honey and tragacanth to a pilular consistence. 
The honey preserves the iodide from oxidation during the evaporation, but 
renders the pills too deliquescent to keep in boxes. — W. P. Jr. 
