Preparation

This is, beyond all comparison, the most important and most extensively used of the preparations of bark, and may be considered as a sufficient representative of its virtues, on all ordinary occasions. For the details of its preparation, the reader is referred to the U. S. Dispensatory. For our purposes here, it is sufficient to state that officinal yellow or Calisaya bark, which is usually selected, is exhausted by boiling it with water acidulated with muriatic or sulphuric acid; that, from the decoction thus obtained, the quinia and other alkaloids are precipitated, together with impurities, by means of lime; that the precipitate is treated with alcohol, which dissolves the alkaloids; that the alcoholic solution is then evaporated; and, finally, that from the residue, consisting mainly of quinia, the sulphate is obtained by treating it with boiling water and sulphuric acid, purifying with animal charcoal, and crystallizing.

Sensible and Chemical Properties. Sulphate of quinia is in minute, white, silky, flexible, needle-shaped crystals, in tufts or interlaced, inodorous, intensely bitter, fusible at 240° F., soluble in 740 parts of cold water, 30 of boiling water, and 60 of alcohol, and very slightly soluble in ether. It is, however, very readily dissolved by water acidulated with almost any one of the sour acids. It is also soluble, to a considerable extent, in glycerin, which, if slightly heated, is said to take up more than one-twelfth of its weight. {Lancet, Am. ed., ii. 202.) Its aqueous solution exhibits a beautiful bluish colour or opalescence on its surface. Two views are taken of its composition; one, that it is a neutral sulphate, containing one eq. of acid and one of base; the other, that it is a disulphate, containing one eq. of acid, and two eqs. of base. The former opinion, which was first entertained, subsequently gave way to the latter; but some chemists are disposed to return to it, and the author has always considered it as most probably correct; so that the ordinary designation of the salt should, in his view, be retained. If it be considered a neutral salt, its exact composition will be expressed by the formula; one eq. of sulphuric acid 40, one of quinia 324, and eight eqs. of water 72 = 436. It loses part of its water of crystallization by exposure, or by heat, but always retains about 4 per cent. or two eqs. of water, from which it cannot be separated without decomposition.

Bisulphate of Quinia. By an additional equivalent of sulphuric acid, the sulphate is converted into the bisulphate, by some considered as the neutral salt. This is much more soluble in water than the ordinary sulphate, requiring only 11 parts of cold water for solution, and is freely dissolved by alcohol. It is formed extemporaneously in solution, with the utmost facility, by gradually dropping a little diluted sulphuric acid into a mixture of the ordinary sulphate with water, until the latter is dissolved.

Incompalibles

The substances which yield precipitates with solutions of sulphate of quinia, and should, therefore, not be administered, as a general rule, along with it, are the alkalies and their carbonates, the alkaline earths, all astringent solutions containing tannic acid, and the soluble salts of lead and baryta. The soluble salts of oxalic, tartaric, and gallic acids also occasion more or less precipitation with solution of sulphate of quinia, without excess of acid; and the same has been ascertained to be the case, by Mr. Maiseh, with the soluble acetates (Am. Journ. of Pharm., xxvii. 97); but the precipitates may be redissolved by the addition of an acid.

Adulteration. Sulphate of quinia is liable to adulteration; but this can generally be easily detected by referring to its peculiar solubilities. The presence of mineral substances, not easily volatilized by heat, will be evinced by a residue left behind when a small portion of the salt is put upon red-hot iron. (See U. S. Dispensatory, 11th ed., p. 1239).

Effects. The properties of sulphate of quinia as a therapeutic agent have already been sufficiently considered. In reference to its antiperi-odic and secondary sedative effects, it has all the power of bark, and more indeed than can always be exerted by the crude medicine. As a mere tonic, it is possible that the compound infusion, or some other preparation in which all the active principles of bark are contained, or the bark itself in substance, may be more efficacious; but I do not think that the fact has been rigidly demonstrated. The peculiar advantages of the salt are its convenience of administration, its general acceptability to the stomach, the rapidity with which it is absorbed, the facility of ascer tabling its purity and genuineness, and the opportunity which it affords, by the smallness of its dose, of obtaining the peculiar effects of bark in a degree greater than can be obtained, as a general rule, from the bark itself.