In the _Yellow Bark_, these chemists discovered also a salifiable base,
quite distinct however in its character and habitudes from _Cinchonia_;
they accordingly have designated it by another name, viz. _Quinine_, but
which we shall hereafter call _Quina_. In speaking of these two bases,
the authors compare them, in point of dissimilarity, to the fixed
alkalies, potass and soda. _Quina_ is distinguished from _Cinchonia_ by
the following characters. It cannot, like this latter body, be
crystallized by evaporation from its alcoholic solution, although it may
be obtained in transparent plates. _It is very soluble in æther_; in
water it is as insoluble as cinchonia, but its taste is much more
bitter. The salts which it forms are different from those of cinchonia,
both in the proportion of their elements, and in the properties which
they possess, being generally much more bitter. In comparing their
composition, _Quina_ will appear to have less capacity of
saturation[464] than cinchonia.
_Sulphate of Quina._ It forms crystals quite remarkable for their
satin-like and pearly lustre. It is soluble in cold water, a property
which is very considerably increased by an excess of acid.[465] It
appears from the observations of M. Callaude, apothecary at Annecy, that
_Sulphate of Quina_ exposed to a gentle heat, becomes highly luminous;
and M. Pelletier has since found that _Sulphate of Cinchonia_, when
exposed in a capsule to the steam of boiling water, exhibits the same
phenomenon, but that neither _Quina_ nor _Cinchonia_, by themselves, nor
their acetates, possess this phosphorescent quality. This appears to be
the most efficient of all the salts of Bark, and is the one from which I
have frequently derived much advantage. In its exhibition we must be
careful not to combine it with substances that form insoluble compounds
with it. The _Infusum Rosæ compositum_ is objectionable as a vehicle, on
account of the astringent matter which it contains, and which therefore
precipitates the _Quina_ from its solution. I have lately seen a
prescription, in which the salt is directed to be rubbed with a few
grains of _Cream of Tartar_, and then to be dissolved in mint water.
This is obviously injudicious, since Tartaric acid decomposes the
sulphate, and occasions an insoluble _Tartrate_, which is precipitated.
The form in which I have usually prescribed it is in that of solution,
with a small quantity of sulphuric acid, in the proportion of a minim to
every grain of the salt. A _Wine of Quina_ may be made by adding five
grains of the sulphate to a pint of Sherry; a Tincture, by dissolving
the same quantity in eight fluid-ounces of Rectified Spirit. The
sulphate is to be preferred to the pure _Quina_ in these cases, because,
when the tincture is made by using the alkali, not saturated by an acid,
a precipitate is formed on adding it to aqueous liquors. Dose of the
Sulphate, gr. i.–v.
_Acetate of Quina_, very remarkable for the great facility with which it
crystallizes, and for the pearly aspect and agreeable stellated grouping
of the crystals; whereas the acetate of cinchonia crystallizes with
difficulty, and simply in plates transparent, and devoid of lustre.
_Quina_ forms with the oxalic, gallic and tartaric acids, salts as
insoluble as those which the same acids form with _Cinchonia_.