The common method for the manufacture of ammonia is to produce it from
the salt known as sal-ammoniac. Sal-ammoniac as a crystal is obtained
in various ways, principally from the ammoniacal liquor of gas works,
also from the condensed products of the distillation of bones and
other animal refuse in the preparation of animal charcoal, and which
is of a highly alkaline nature. This liquid is then treated with a
slight excess of muriatic acid to neutralize the free alkali, and at
the same time the carbonates and sulphides are decomposed with the
evolution of carbonic acid and sulphureted hydrogen. All animal
matter, the meat, bones, etc., contain considerable carbon, while the
nitrogen from which the ammonia is produced forms a smaller portion of
the substance. The object is then to get rid of the carbon and
sulphur, leaving the nitrogen to combine, through chemical affinity,
with a portion of the hydrogen of the water, the oxygen which is set
free going to form the carbonic acid by combining with the carbon. The
liquor after being neutralized is evaporated to dryness, leaving a
crystallized salt containing a portion of tarry matter.
The salt is then purified by sublimation, that is, it is heated in a
closed iron vessel until it is transformed into a gas which separates
and leaves, in a carbonized state, all foreign substance.
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