Aquae Medicatae.—Medicated Waters.
These consist of water holding in solution some medicinal or aromatic principles, as certain gases, volatile oils etc. Heretofore those waters which contained a portion of the aroma of certain plants, were procured by distilling water from either the fresh or dry herb; the principal portion of the volatile oil which collected on the top of the distillate upon standing, was removed, a sufficient amount being retained by the water to render it of the taste and odor of the plant. But such distilled waters are very apt to become spoiled, unless great care be taken to redistill them from time to time, or add to them some preservative material which is frequently an undesirable addition. It has, therefore, been found the best method to triturate the essential oil itself with certain substances in the water, which so minutely divide the former as to render it more soluble in the latter, as carbonate of magnesium, pumice stone, finely powdered glass or silica, etc., which yield a clear and permanent solution after being filtered through paper. Carbonate of magnesium was, previous to 1880, the medium more commonly employed in this country. The U. S. P. now directs precipitated calcium phosphate. As ordinary water contains several agents which may decompose or ultimately destroy the aromatic virtues imparted to it by the above method, it is of much importance that distilled water only be always used. T. B. Groves succeeded in recovering volatile oils from their watery solutions, by first adding to them olive oil, and then saponifying with potash. The soap thus formed, when decomposed by an acid, liberates the mixed oils, from which the aromatic portions may be separated by shaking with alcohol (Pharm. Jour. and Trans., p. 347, Feb., 1864).
Medicated waters have been made by adding to a few pounds of the leaves or flowers of the article required, 6 or 7 fluid ounces of proof-spirit, and 2 gallons of water; from which 1 gallon is distilled. In this way was formerly obtained nearly all of these preparations, but the processes given below are now esteemed the best. Aqua Aurantii Florum, orange-flower water, Aqua Foeniculi, fennel water, Aqua Menthae Piperitae, peppermint water, Aqua Menthae Viridis, spearmint water, together with several others, may be procured from the plants or flowers, by the mode of distillation just referred to. The U. S. P. of 1880, directed the preparation of several of the medicated waters prepared from oils by adding to cotton a few drops at a time of the desired oil, carefully picking the cotton apart after each addition, after which the cotton was packed firmly in a conical percolator, and upon it distilled water was poured until the percolate measured 1000 parts. By this method it was found that either not enough of the oil was taken up by the water, or else free globules of oil passed through into the percolate, thus rendering it of uncertain strength. This method has been abolished. The objection to the use of magnesium carbonate, which was formerly employed in making these waters also, is that the salt itself is slightly soluble in water, so that when a substance like silver nitrate was directed to be dissolved in such a water, a precipitate of silver carbonate was thrown down. It has been replaced by precipitated calcium phosphate.