en pounds of lime,
previously slaked, and made into a milky mixture with two and a half
gallons of water; then cover the vessel, and continue the steaming for
several hours, or until the saponification shall be completed. This may
be known when a sample of the soap when cold gives a smooth and bright
surface on being scraped with the finger-nail, and at the same time,
breaks with a crackling noise. By this process the fat or oil is
decomposed, its acids uniting with the lime to form insoluble lime-soap,
while the eliminated glycerine remains in solution in the water along
with the excess of the lime. After it has been sufficiently boiled, it
is allowed to cool and to settle, and it is then to be strained.

The strained liquid contains only the glycerine and excess of lime, and
requires to be carefully concentrated by heated steam. During
evaporation, a portion of the lime is deposited, on account of its
lesser solubility in hot than in cold water. The residue is removed by
treating the evaporated liquid with a current of carbonic acid gas,
boiling by heated steam to convert a soluble bicarbonate of lime that
may have been formed into insoluble neutral carbonate, decanting or
straining off the clear supernatant liquid from the precipitated
carbonate of lime, and evaporating still further, as before, if
necessary, so as to drive off any excess of water. As nothing fixed or
injurious is employed in this process, glycerine, prepared in this
manner, may be depended upon for its almost absolute purity.

M. Jahn's process is as follows:--

Take of finely-powdered litharge five pounds, and olive oil nine pounds.
Boil them together over a gentle fire, constantly stirring, with the
addition occasionally of a small quantity of warm water, until the
compound has the consistence of plaster. Jahn boils this plaster for
half an hour with an equal weight of water, keeping it at the same time
constantly stirred. When cold, he pours off the supernatant fluid, and
repeats the boiling three times at least with a fresh portion of water.
The sweet fluids which result are mixed, and evaporated to six pounds,
and sulphuretted hydrogen conducted through them as long as sulphuret
of lead is precipitated. The liquid filtered from the sulphuret of lead
is to be reduced to a thin syrupy consistence by evaporation. To remove
the brown coloring matter, it must be treated with purified animal
charcoal. However, this agent does not prevent the glycer