or of cold has
been hitherto capable of reducing it either to a solid or liquid form.
This is likewise one of the essential constituent elements of animal
bodies, in which it is combined with charcoal and hydrogen, and
sometimes with phosphorus; these are united together by a certain
portion of oxygen, by which they are formed into oxyds or acids
according to the degree of oxygenation. Hence the animal substances may
be varied, in the same way with vegetables, in three different manners:
1st, According to the number of elements which enter into the
composition of the base or radical: 2dly, According to the proportions
of these elements: 3dly, According to the degree of oxygenation.

When combined with oxygen, azote forms the nitrous and nitric oxyds and
acids; when with hydrogen, ammoniac is produced. Its combinations with
the other simple elements are very little known; to these we give the
name of Azurets, preserving the termination in _uret_ for all
nonoxygenated compounds. It is extremely probable that all the alkaline
substances may hereafter be found to belong to this genus of azurets.

The azotic gas may be procured from atmospheric air, by absorbing the
oxygen gas which is mixed with it by means of a solution of sulphuret of
potash, or sulphuret of lime. It requires twelve or fifteen days to
complete this process, during which time the surface in contact must be
frequently renewed by agitation, and by breaking the pellicle which
forms on the top of the solution. It may likewise be procured by
dissolving animal substances in dilute nitric acid very little heated.
In this operation, the azote is disengaged in form of gas, which we
receive under bell glasses filled with water in the pneumato-chemical
apparatus. We may procure this gas by deflagrating nitre with charcoal,
or any other combustible substance; when with charcoal, the azotic gas
is mixed with carbonic acid gas, which may be absorbed by a solution of
caustic alkali, or by lime water, after which the azotic gas remains
pure. We can procure it in a fourth manner from combinations of ammoniac
with metallic oxyds, as pointed out by Mr de Fourcroy: The hydrogen of
the ammoniac combines with the oxygen of the oxyd, and forms water,
whilst the azote being left free escapes in form of gas.

The combinations of azote were but lately discovered: Mr Cavendish first
observed it in nitrous gas and acid, and Mr Berthollet in ammoniac and
the prussic acid. As no evi