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to be protected from heat and light. At a low temperature, they keep
indefinitely: exposed to heat, they are liable to lose water of crystallisation and
to become decomposed. Exposed to sunlight they acquire—whether in the
solid form or in solution—a yellowish or brown colour. Flückiger¹⁸ named this
brown product "quiniretin" and found it had the same composition as
Quinine, but was destitute of its alkaline re-action; and, although soluble
in acids, it could not neutralise them. Heat seems to accelerate this change
in Quinine; and boiling, whether for purposes of sterilization or of hastening
solution, produces this change in some of these Quinine preparations in a
few minutes. Quinine, hydrochloride, besides being much more soluble than
Quinine sulphate, contains a larger proportion of Quinine base and is much
less irritating to mucous surfaces (stomach and rectum): its solutions are less
likely to become mouldy, but are said¹⁰ to be much less stable than those of
the sulphate.

      Besides deterioration due to exposure to heat and light, solutions of
Quinine salts are prone to become infected with moulds. In the literature
on the subject solutions of Quinine sulphate alone are spoken of in this
connection. According to Marshall,⁶ "Quinine in general is fatal to moulds,
but on standing exposed to the air solutions of Quinine sulphate quickly
become infected with the common Penicillium, which grows rapidly."
Solutions of the various Quinine salts were kept in stoppered tube-bottles in
the laboratory (Edinburgh University) for over three months, the bottles being
opened and examined periodically. The sulphate solutions were the most liable
to mould infection. The solution of Quinine sulphate with tartaric acid became
infected very quickly and showed luxuriant mould growths under two weeks.
Flavouring agents, such as syrupus aurantii, still further favour the growth of
moulds, especially Penicillium glaucum. In these experiments the growth of
moulds was not limited to the solution of Quinine sulphate and the genus of
fungus was not confined to Penicillium. In luxuriance of mould growth,
solutions of Quinine quinate and Quinine bi-hydrobromide ranked next to
those of the sulphate. Growths were also present, but scanty, in solutions of
bi-hydrochloride, bi-sulphate, urea bi-hydrochloride, lactate and arsenite.
The genus Mucor, as judged from zygospore formation, was present in one
or two instances, but the Perisporiaceœ predominated. Both genera,
Aspergillus and Penicillium with their respective gonidiophores were in
evidence, the former being almost as common as the latter. Perithecia,
indicating the less frequent mode of reproduction, were observed in solutions
of bi-hydrobromide, lactate and arsenite. It would appear therefore that
Quinine is not so inimical to the higher members of fungi as to the lower
yeast forms, which are said⁶ to be as susceptible as bacteria to its action.

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