168 
ON PERCHLORIDE OF IRON. 
the retort, which is to be broken when cold, and the salt 
immediately enclosed in bottles. 
Although the second of these two processes is the better 
and more easy of execution, yet many pharmaceutists would 
find a difficulty in preparing it; moreover, the Codex orders 
as the medicinal perchloride of iron that which is prepared 
by the moist way. 
Several processes have been proposed for making the hy- 
drated perchloride of iron, which I will describe. 
The Codex orders the red oxide of iron to be dissolved 
in hydrochloric acid, and the solution evaporated to dry- 
ness in a water-bath. This process is a bad one; because, 
however carefully it may be evaporated, the product al- 
ways contains a large proportion of insoluble oxychloride. 
MM. Thenard, Berzelius, and Orfila recommend in their 
works to prepare it by dissolving sesquioxide of iron in hy- 
drochloric acid, evaporating the solution to the consistence 
of syrup, and allowing it to cool. The perchloride is de- 
posited in fine red crystals, which are very deliquescent. 
M. Beral has proposed to prepare it by dissolving pre- 
cipitated sesquioxide of iron in hydrochloric acid, first with- 
out heat, and then with the heat of a water-bath ; the so- 
lution is transferred to a porcelain capsule, and evaporated 
at a gentle heat to the consistence of syrup. When it has 
arrived at this point, the capsule containing the perchloride 
of iron is placed by the side of another capsule, containing 
caustic potash or lime, and the whole covered by a bell-glass. 
The alkali absorbs the water and hydrochloric acid, so that 
in ten or fifteen days the chloride becomes a dry, imper- 
fectly crystallized mass. To keep the salt dry, it should be 
at once put into a bottle, before it becomes affected by the 
external air. This method answers very well, but it has 
the disadvantages of requiring a good deal of time, and 
affording a chloride which is not always uniform in compo- 
sition, as it contains variable proportions of water, owing 
to the method adopted in its preparation. 
