It is very important that the water employed for making decoctions, should be free from that quality which is denominated hardness.
The officinal decoctions may be classed into simple and compound preparations.
1. Simple.
Decoctum Cinchonæ. See Cinchona, and Form: 41, 42, 127. The codex of Paris directs a decoction of bark, “Decoctum Kinœ Kinœ,” which is only half the strength of ours, but contains an addition of a small quantity of carbonate of potass.
Decoctum Cydoniæ. The inner coats of the seeds of the Quince (Pyrus Cydonia) yield a very large proportion of mucilage, but as hot water extracts from them also fecula and other principles, the decoction very soon decomposes. It has been strongly recommended as an application to erysipelatous surfaces; and it would seem to be peculiarly adapted for such a purpose, since it is not so easily washed away from the part to which it is applied, as ordinary mucilage; for the same reason it has been preferred as an ingredient in injections, gargles, &c. It is stated by some practitioners to be a very useful application, when united with the acetate of lead, in cases of acute ophthalmia; such a combination, however, is extremely unchemical, and must invalidate the powers of the other ingredients. The native practitioners of India employ it as a cooling mucilaginous drink in gonorrhœa. An ounce of bruised Quince seed will make three pints of water as thick and ropy as the white of an egg; hence two drachms, the quantity directed by the College, is amply sufficient for a pint of the decoction. It is coagulated by alcohol, acids, and metallic salts.
Decoctum Digitalis. D. This is a very improper form for the exhibition of digitalis, being variable in strength.
Decoctum Dulcamaræ. L. In making this decoction we must take care that the operation of boiling is not continued too long. See Dulcamaræ Caules. Dose from f℥ss to f℥j.
Decoctum Lichenis. L.E.D. In this preparation we have the bitter principle of the plant united with its fecula. A portion of the former may be removed by macerating the lichen, and rejecting the first water. If ℥j of the mass be boiled for a quarter of an hour in f℥vj of water, we shall obtain mucilage of a consistence similar to that composed of one part of gum arabic and three of water. Its exhibition requires the same precaution as that of Mucilago Acaciæ. From the large proportion of fecula which this moss contains, it is perhaps as nutritive as any vegetable substance, the Cerealia of course excepted. See Lichen Island. Dose, a wine glass full occasionally.
Decoctum Papaveris. L. In making this decoction the whole of the capsule should be bruised, in order to obtain its mucilage and anodyne principle; the seeds should be also retained, as they yield a portion of bland oil which increases the emollient quality of the decoction. A large quantity of fixed oil is constantly in the market, which is derived from the seeds of the poppy. This decoction is a useful fomentation in painful swellings, &c.
Decoctum Quercus. L.E. Decoction is the usual form in which Oak Bark is exhibited, since all its active principles are soluble in water. Its astringent virtues depend upon gallic acid, tannin, and extractive. The decoction is disturbed by the following substances; the infusion of yellow cinchona; sub-acetate and acetate of lead; solutions of isinglass; the preparations of iron; oxy-muriate of mercury; and sulphate of zinc; all alkaline substances destroy its astringency, and are consequently incompatible with it. It is principally useful as a local astringent, in the forms of gargle, injection, or lotion. Its internal exhibition in obstinate diarrhœas, and alvine hemorrhages, has also proved highly beneficial. See Form: 51, 61. Dose, f℥ss to f℥j. Dr. Eberle states that in the Intermittents of very young children, he has in some cases used this decoction as a bath with efficacy.