mery value, because
it is free from the volatile oil which, as above stated, gives it its
peculiar odor. The wet method devised by Scheele is as follows:--Make
one ounce of freshly-burnt lime into a milk with from four to six ounces
of hot water. To the milk of lime, four ounces of powdered benzoin and
thirty ounces of water are to be added, and the mixture boiled for half
an hour, and stirred during this operation, and afterwards strained
through linen. The residue must be a second time boiled with twenty
ounces of water and strained, and a third time with ten ounces; the
fluid products must be mixed and evaporated to one-fourth of their
volume, and sufficient hydrochloric acid added to render them slightly
acid. When quite cold, the crystals are to be separated from the fluid
by means of a linen strainer, upon which they are to be washed with cold
water, and pressed, and then dissolved in hot distilled water, from
which the crystals separate on cooling. When hydrochloric acid is added
to a cold concentrated solution of the salts of benzoic acid, it is
precipitated as a white powder. If the solution of the salts of this
acid is too dilute and warm, none or only a portion of the benzoic acid
will be separated. However, the weaker the solution is, and the more
slowly it is cooled, the larger will be the crystals of this acid. In
the preparation of this acid in the wet way, lime is to be preferred to
every other base, because it forms insoluble combinations with the
resinous constituents of the benzoin, and because it prevents the
gum-resin from conglomerating into an adhesive mass, and also because an
excess of this base is but slightly soluble.

Stoltze has recommended a method by which all the acid can be removed
from the benzoin:--The resin is to be dissolved in spirit, to which is
to be added a watery solution of carbonate of soda, decomposed
previously by alcohol. The spirit is to be removed by distillation, and
the remaining watery solution, from which the resin has been separated
by filtration, treated with dilute sulphuric acid, to precipitate the
benzoic acid. This method gives the greatest quantity of acid, but is
attended with a sacrifice of time and alcohol, which renders it in an
economical point of view inferior to the above process of Scheele. It
is so far valuable, that the total acid contents of the resin can be
determined by it.

Dr. Gregory considers the following process for obtaining benzoic acid
t