They will be considered under _Ammonia_.
SODIUM.
Sodium is the commonest of the alkali metals. It is found in nature
chiefly combined with chlorine as "common salt" (NaCl). This mineral is
the source from which the various compounds of sodium in use are
prepared. Sodium occurs abundantly as nitrate (NaNO_{3}) in Chili
saltpetre, and as silicate in various minerals, such as albite (or
soda-felspar).
It occurs as fluoride in cryolite (Na_{3}AlF_{6}), and as carbonate in
natron, &c. Sulphates are also found. Sodium is very widely diffused,
few substances being free from it.
The detection of sodium is easy and certain, owing to the strong yellow
colour its salts impart to the flame; this, when viewed by the
spectroscope, shows a single yellow line.[93] The extreme delicacy of
this test limits its value, because of the wide diffusion of sodium
salts. It is more satisfactory to separate the chloride, which may be
recognised by its taste, flame coloration, fusibility, and negative
action with reagents. The chloride dissolved in a few drops of water
gives with potassium metantimoniate, a white precipitate of the
corresponding sodium salt.
Sodium salts are dissolved out from most compounds on treatment with
water or dilute acids. Insoluble silicates are decomposed and the alkali
rendered soluble by Lawrence Smith's method, which has just been
described.
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