In the other process no
sand is used, but the dry mixture is dissolved in water, and the soap
solution which holds the neutral oils in solution is treated with ether,
which dissolves out the neutral oil and then floats to the surface of
the liquid. The ether solution is then drawn off, and the ether in the
one case and petroleum spirit in the other are separated from the
dissolved oils by distillation, the last traces of these volatile
liquids being separated by blowing a current of filtered air through
the flask containing the neutral oil, which is then weighed and its
percentage on the original sample calculated.
All animal and vegetable oils yield a small quantity--about one per
cent.--of unsaponifiable fatty matter, which must be deducted from the
result obtained. Sperm oil, however, was found to be an exception,
because from its peculiar chemical constitution it yields nearly half
its weight of a greasy substance to the ether or to the petroleum
spirit. The substance, however, dissolved from sperm oil after
saponification has the appearance of jelly, when the ether or petroleum
spirit solution is concentrated and allowed to cool, and the presence of
sperm oil can thus be readily detected. Solid paraffin, heavy petroleum
or paraffin oils, and rosin oil--which is produced by the destructive
distillation of rosin--are not saponifiable, and yield about the whole
of the amount employed to the petroleum spirit or ether.
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