PREPARATION OP THE PERCHLORIDE OF IRON. 143 
dome, and into the neck of the retort; when this has cool- 
ed sufficiently, it is broken, the chloride removed and trans- 
ferred immediately into the bottles destined to receive it. 
Although the last of the two processes described is the 
best and most easy of execution, there are many phar- 
maceutists who are prevented from following it, and the 
medicinal perchlordide of iron of the Codex is that which 
is obtained by the moist way. Several processes have been 
proposed for the preparation of the hydrated perchloride of 
iron. The Codex prescribes dissolving red oxide of iron in 
hydrochloric acid and evaporating the solution to dryness 
over the water-bath. This process is bad, for the product 
always contains, however carefully the evaporation may 
have been made, a large proportion of insoluble oxy chloride. 
Thenard, Berzelius and Orfila advise, in their works, dis- 
solving sesquioxide of iron in hydrochloric acid, evaporat- 
ing the solution to a syrupy consistence, and allowing to 
cool. The perchloride is deposited in the form of beautiful 
red crystals, which deliquesce with the greatest facility. 
M. Beral proposed preparing it by dissolving precipi- 
tated sesquioxide of iron in hydrochloric acid, first cold and 
then over a water-bath; the solution is transferred into a 
porcelain capsule, and evaporated at a gentle heat to a 
syrupy consistence ; when arrived at this point, the capsule 
containing the perchloride of iron is placed by the side of 
another containing caustic potash or lime, and the whole 
covered with a bell-glass. The alkali absorbs both the 
water and the hydrochloric acid, so that in ten to fifteen 
days the chloride forms a dry, confusedly-crystallized mass 
which is then transferred into a bottle under the bell-glass, 
to prevent the salts deliquescing in the air. This process 
succeeds very well, but it requires much time, and gives a 
chloride which is not of constant composition, because 
it retains variable quantities of water, owing to the method 
of its preparation. 
M. Morh has recently proposed for preparing perchlori- 
