3. We may supersaturate slightly the two bases with sulphuric acid. Now
as the supersulphate of quinina is sparingly soluble, the liquor need
only to be evaporated to a proper point to crystallize out that salt,
while the supersulphate of cinchonina continues in solution with very
little of the other salt. Even this may be separated by precipitating
the bases, and treating them, as above prescribed, with alcohol or
ether.
One pound of bark rarely yields more than 2 drams of the bases. One
pound of red bark afforded, to Pelletier and Caventou, 74 grains of
cinchonina, and 107 grains of quinina.
Quinina is composed of 75·76 carbon, 7·52 hydrogen, 8·11 azote, and 8·61
oxygen.
The salts of quinina are distinguished by their strong taste of Peruvian
bark, and if crystallized, by their pearly lustre. Most of them are
soluble in water, and some also in ether and alcohol. The soluble salts
are precipitated by the oxalic, gallic, and tartaric acids, and by the
salts of these acids. Infusion of nutgalls also precipitates them.
The sulphate of quinina is the only object of manufacturing operations.
Upon the brownish viscid mass obtained in any of the above processes for
obtaining quinina, pour very dilute sulphuric acid, in sufficient
quantity to produce saturation. The solution must be then treated with
animal charcoal, filtered, evaporated, allowed to cool, when it deposits
crystals. 1000 parts of bark afford, upon an average, 12 parts of
sulphate. The sulphate of cinchonina, which is formed at the same time,
remains dissolved in the mother-waters.
The neutral sulphate of quinina occurs in small transparent right
prismatic needles. By spontaneous evaporation of their solution, larger
crystals may be procured. They contain 24-2/3 per cent. of water; and,
therefore, melt when exposed to heat. They dissolve in 11 parts of water
at ordinary temperatures; are much more soluble in hot spirit of wine,
somewhat dilute, than in cold; and are nearly insoluble in anhydrous
alcohol. If they be well dried, they possess the property of becoming
luminous when heated a little above the boiling point of water,
especially when they are rubbed. The sulphate is, in this case, charged
with vitreous electricity.
There is a sub-sulphate, but it is applied to no use. The effloresced
sulphate, called by some bisulphate, is preferred for medical practice.
The extensive sale and high price of sulphate of quinina, have given
rise to many modes of adulteration. It has been mixed with boracic acid,
margaric acid, sugar, sugar of manna, gypsum, &c. By incinerating a
little of the salt upon a slip of platina, the boracic acid and gypsum
remain, while the quinine is dissipated; sugar and margaric acid exhale
their peculiar smoke and smell; or they may be dissolved out by a few
drops of water. Cinchonina may be detected by adding ammonia to the
solution, and treating the precipitate with ether, which leaves that
vegeto-alkali.
QUINTESSENCE. The alchemists understood by this term, now no longer in
scientific use, the solution in alcohol of the principles which this
menstruum can extract from aromatic plants or flowers, by digestion,
during some days, in the sun, a stove, or upon a sand-bath slightly
warmed. A quintessence, therefore, corresponds to the alcoholic tincture
or essence (not essential oil) of the present day. See PERFUMERY.