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MERCURY.
425
mercurous sulphate and chloride of sodium, a double decomposi-
tion taking place, by which mercurous chloride and sulphate of
sodium are formed. The mercurous sulphate thus employed is
obtained by boiling mercury in sulphuric acid and triturating
the resulting mercuric sulphate with mercury.
To remove any corrosive sublimate which the calomel may
contain, it is washed with hot distilled water until the absence of
a white precipitate with ammonia shows that the poisonous in-
gredient has been removed. Calomel is in the form of a white,
inodorous, tasteless powder, insoluble in water, alcohol and ether,
and wholly volatilized by heat. Calomel is incompatible with
the alkalies, and alkaline earths, and alkaline carbonates, with lead,
copper and iron. When nitro-muriatic acid is combined with it,
corrosive sublimate is formed ; neither should it be given in com-
bination with iodine.
Medical Properties and Action.—Calomel and the other mercurials
are employed as alteratives, sialagogues, purgatives, diuretics, etc.,
and moderate doses increase the action of the secreting glands
and organs, stimulating the salivary glands in a very decided man-
ner. When large doses are administered the effects are manifested
on the gums, which become tender and swollen, the salivary
glands take on increased action, the saliva and buccal mucus flow
profusely, the mucous membrane of the mouth becomes inflamed
and ulcerated, the tongue swollen and the breath fetid, with a
metallic, copper taste, and the teeth become loose ; such symp-
toms constitute the condition known as salivation. When the
use of the drug is discontinued these symptoms disappear, but the
mucous membrane and gums are ever after more susceptible to
irritation, and the stability of the teeth is more or less impaired,
as is shown by the recession of the gums and the absorption of
the alveolar processes. In many cases the gums, especially about
the necks of the teeth, remain somewhat tumefied, with a
tendency to ulceration.
If the use of the mercury is continued beyond the stage which
the symptoms just described indicate, or even as the effects of
small doses in persons very susceptible to the influence ot mer-
cury, an excessive salivation ensues, with serious ulceration of