,
which appears as a long brilliant stream and considerably increased in
volume. The presence of potash does not prevent this reaction of soda.
If there is too large a quantity of potash, the flame near to the
substance is violet-colored, but the edge of the flame exhibits the
characteristic tint of the soda. The presence of lithia changes the
yellow color to a shade of red.

When alcohol is poured over powdered soda compounds and lighted, the
flame exhibits a reddish-yellow color, particularly if the alcohol is
stirred up with a glass rod, or if the alcohol is nearly consumed.

Fused upon charcoal, soda compounds are absorbed by the coal. The
sulphide, chloride, iodide, and bromide of soda yield a white
sublimate around the spot where the substance is laid, but this
sublimate is not so copious as that of the potash compounds, and
disappears when touched with the reduction flame, communicating a
yellow color to the external flame. The presence of soda in compounds
must likewise be confined by reactions in the wet way.

(_c._) _Ammonia_ (NH^{4}O).--In the fused state, and at the usual
temperature, ammonia is a pungent gas, and exerts a reaction upon
litmus paper similar to potash and soda. Ammonium is considered by
chemists as a metal, from the nature of its behavior with other
substances. It has not been isolated, but its existence is now
generally conceded by all chemists. The ammonia salts are volatile,
and many of them sublimate without being decomposed.

The salts of ammonia, on being heated in the point of the blue flame,
produce a feeble green color in the external flame, just previous to
their being converted into vapor. But this color is scarcely visible,
and presents nothing characteristic. When the ammonia salts are mixed
with the carbonate of soda, and heated in a glass tube closed at one
end, carbonate of ammonia is sublimed, which can be readily recognized
by its penetrating smell of spirits of hartshorn.

This sublimate will render blue a slip of red litmus paper. This can
be easily done by moistening the litmus paper, and then inserting the
end of it in the tube. By holding a glass rod, moistened with dilute
hydrochloric acid, over the mouth of the tube, a white vapor is
instantly rendered visible (sal ammoniac).

(_d._) _Lithia_ (LiO).--In the pure state, lithia is white and
crystalline, not easily soluble in water, and does not absorb
moisture. It changes red litmus to blue, and at a low red heat