The term tincture is usually, although improperly, applied to spirituous solutions of such of the proximate principles of vegetables and animals as are soluble in pure alcohol or in proof spirit. From vegetable matter submitted to its action, alcohol takes up sugar, resin, extractive, tannin, cinchonia, quina, piperina salicina, camphor, guaiacum, volatile oils, several acids, veratria, strychnia, aconitina, scillitina, elatin, morphia, and narcotina; proof spirit also takes up the whole of these partially, and is, besides, the proper menstruum for gum resins; so that alcohol, either in a concentrated or diluted form, is capable of separating the greater part of the active principles of vegetables from the ligneous inert fibres. The tinctures obtained from animal substances are very few in number, and the principles taken up by the spirit are analogous to those enumerated above, belonging to the vegetable kingdom. Pure alcohol is required in a very few instances only for the formation of tinctures, proof spirit being adequate for almost every purpose.

The dilution of the spirit, however, must be varied according to the known principles of the substance to be submitted to its action: when resin predominates, it must necessarily be more concentrated; when gum-resin or extractive is the most abundant constituent, proof spirit then must be employed. In consequence of the great affinity of water for alcohol, the addition of it to alcoholic tinctures separates the resin, camphor, and volatile oils they contain; but water is generally miscible with tinctures made with proof spirit, without producing any decomposition. Tinctures are not liable to suffer spontaneous decomposition, as is the case with infusions and decoctions; and, independent of the loss which takes place from the evaporation of the spirit and the volatile oils, if the bottles containing tinctures be closely corked, they may be kept for an indefinite length of time, and their virtues remain unimpaired.

1 Arnold de Villa Nova, who was professor of medicine at Montpellier, invented tinctures about the end of the 13th century. The term is a bad one, as, strictly speaking, it means a solution prepared for dyeing. Spirituous solutions would be more appropriate.

Tinctures are prepared by macerating the ingredients in the spirit in a temperature not exceeding 80°, at which degree, by allowing the menstruum to remain on the ingredients for a sufficient length of time, all the principles that can prove useful in the tincture are extracted, and the solvent saturated. The ingredients must be dried, and reduced to a coarse powder, and the maceration made in close vessels, and assisted by frequent agitation. When completely made, tinctures should not be allowed to remain upon the ingredients, but be filtered through bibulous paper, and kept in this state in well-corked bottles. Parmentier1 has proposed that one half only of the spirituous menstruum be added to the ingredients at first; and, after digesting for six days, this part is to be poured off, and the remainder added. In six more the whole is to be strongly expressed, and the two portions of tincture mixed together. By this method he imagines more of the active principles of the ingredients are extracted, and the tinctures obtained of a more uniform strength.

Tinctures are not of very extensive use as remedies, except in cases where stimulants are indicated; the solvent, even in doses of a few fluid drachms, often acting more powerfully on the living system than the principles it holds in solution. In ordinary cases, this action, when continued for some time,

1 Annales de Chimie, lxii. 40, 3 Y produces the same deleterious effects as the habitual use of ardent spirits; and often lays the foundation of the pernicious custom of dram drinking. When the action of a substance is the reverse of stimulant, it cannot with propriety be exhibited in this form, unless the dose be so small that the operation of the spirit cannot be taken into account, as in tincture of foxglove. The chief use of this class of preparations, therefore, is to enable infusions and decoctions, to which they are added, to sit lighter on the stomach, or to add to them some active principle which water is incapable of extracting.

The general rule given in the London Pharmacopoeia for the preparation of tinctures is "to prepare them in closed vessels, and to shake them frequently during the maceration."