TINCTURES are solutions of the active principles, mostly of vegetables, sometimes of saline medicines, and more rarely of animal matters, in certain solvents. From possessing more or less of colour, they have obtained this name. They are distinguished according to the kind of solvent employed. When alcohol is used, they are termed alcoholic tinctures, or more generally simply tinctures; when sulphuric ether is used, they are denominated ethaial tinctures. When wine is used, though differing little from pure alcohol, the term medicated wines is applied to them ; and when the process of distillation is employed to aid the extraction, particularly of volatile oils, the result is termed a spirit, such as of rosemary. Ammonia is sometimes con joined, and the proceeds termed an ammoniated tincture. In some cases less of the principal ingredient is taken up or dissolved when ammonia is used, than when simple alcohol is employed, as in the tinctura guaiaci ammoniata. Formerly some tinctures were called essences, from the term ease, it being thought that they contained only the purer or more refined portion, the alcohol leaving all the baser principles, such as the starch, gum, woody fibre, undissolved : quintessence was a still higher degree of this. These terms are now disused by pharmaceutists, though retained iu popular language. Elixirs differ only from being of a greater consistence : they are not unfre quently turbid from the extractive matter suspended in them. Tinctures are further distinguished into simple and compound. They are called simple when one substance only is submitted to the solvent ; compound, when two or more are. Another important distinction among tinctures is founded upon the degree of strength of the alcohol employed. Where the active principle is nearly pure resin, a strong spirit is needed ; when much gum is associated with the resin, a weaker is required. Hence some tinctures are prepared with proof spirit, as the greater number ; a few with spirit above proof; and some with rectified spirit.
A well prepared tincture should be clear, possessing the colour of the article which is its base, and partaking in an eminent degree of its characteristic odour and taste. As a general rule, five or six parts of the liquid chosen is to be used for one part of the solid material, which is to be bruised or comminuted before being submitted to maceration. The maceration, which should be conducted in well-stopped glass vessels, is generally continued for fourteen days, during which the ingredients are to be frequently shaken, and at the end strained. The
process of displacement by percolation is also good. The pure tincture is then to be preserved in a tightly-stopped bottle, which should be opaque, or sheltered from the light. From several tinctures a deposit falls down, either from some slow chemical change taking place among the ingredients, or from the evaporation of some of the spirit. This renders old tinctures not unfreqnently turbid, and of variable strength. Thus tincture of opium when newly prepared contains one grain of opium in nineteen minims, but after some time one grain of opium is contained in only fourteen minims. This inconvenience may be avoided with all recent vegetables, by forming what are termed "vegetable juices." These are merely the juices of the fresh plant expressed by a powerful wooden press, and the juice allowed to stand twenty-four hours, during which a copious precipitation of feculent matter takes place, which is further promoted by adding alcohol over proof, in the proportion of four fluid ounces to every sixteen fluid ounces of the Juice. After standing for twenty-four hours, the juice is to be filtered through bibulous paper (prepared from wool), when It will keep unimpaired for a length of time.
These vegetable juices always retain their purity, and are of the same degree of strength at last as at first. By this means not only is the process simplified, and the time required for their preparation greatly abridged, being reduced from fourteen days to two ; but their medicinal efficacy is greater than that of the ordinary tinctures, and, from containing less alcohol, they can be given in cases where the stimulating action of this principle interferes with the effect of the substance dissolved in it, or renders its exhibition improper, as iu the case of young children.
In preparing the officinal spirits, the directions of the Pharmacopceia are rarely complied with. Most chemists content themselves with dissolving some of the essential oil of the plant in alcohol of the requisite strength, by which much expense and trouble, as well as loss of time, are avoided.
(See a pamphlet on The Best Method of Obtaining the Most Powerful Vegetable Preparations for Medical Use, by Edward Bentley.)