2. Drop fʒiiiss of nitric acid upon fʒj of rectified oil of amber; after standing twenty-four hours, a black, resinous pellicle, exhaling the odour of musk, will be formed.
MUCILAGO ACACIÆ. L.E.
Mucilago Gummi Arabici. D.
This preparation consists of one part of gum and two of water; in preparing it, the dispenser is particularly recommended to pulverize the gum, and never to employ that which is purchased in the state of powder, as it is always impure and incapable of forming a pellucid and elegant solution.[[564]] Incompatible Substances. Neither the strong acids nor alcohol, when considerably diluted, occasion any disturbance in it; but sulphuric æther and its compound spirit, the tincture of muriated iron, and sub-acetate of lead, produce very dense precipitates: the acetate of lead only occasions decomposition, when an alkaline salt is present in the formula; the volatile alkali curdles the mucilage, and hard calcareous waters render the mixture difficult and often impracticable. In the pharmaceutical application of this mucilage, it should be remembered that it contains in its composition an astringent principle, which is perhaps of but trifling consequence except in the exhibition of some very few active metallic salts, which are certainly decomposed by it (e. g. grs. x of nitrate of mercury are decomposed by ʒij of gum arabic.[[565]]) It contains also lime in combination with some vegetable acid. Uses. Diluted with four times its bulk of water, this mucilage forms a demulcent mixture of appropriate tenacity, which affords a convenient vehicle for several efficient remedies; the pharmaceutical use of this mucilage depends upon the fact of its rendering expressed and essential oils, balsams, resins, gum-resins, resinous tinctures, and fatty bodies, miscible with water, but if a syrup be added, the union will be more perfect; the proportions necessary for this purpose vary according to the nature of the substances; thus, oils will require about three-fourths their weight, Balsams and Spermaceti an equal part, Resins a double quantity, and Musk five times its weight; the following Formulæ illustrate this property, 9, 19, 22, 135.
MUCILAGO AMYLI. L.E.D.
Mucilage of Starch.
This is a strong, insipid, inodorous mucilage, which is principally employed as a vehicle for exhibiting Opium in the form of Enema, see Amylum.
MUCILAGO ASTRAGALI TRAGACANTHÆ. E.D.
Tragacanth Mucilage.
Tragacanth is, strictly speaking, not soluble in water, but imbibes a large portion of it and swells into a considerable bulk, forming a soft but not a liquid mucilage; on the farther addition of water, a fluid solution may be obtained by agitation, and the liquor is turbid; but on standing, the mucilage subsides, the limpid water on the surface retaining a little of the gum;[[566]] it differs from all gums in giving a thick consistence to a larger quantity of water, its power in this respect being to that of gum arabic as twenty to one; one part converts twenty of hot water into a stiff mucilage. Tragacanth is not increased, but actually diminished in solubility by the addition of any other gum, it accordingly separates from water with much greater facility when gum arabic is present. This preparation, according to the Edinburgh college, consists of one part of gum and eight of water; the resulting mucilage is stiff, and is principally employed for making troches. The Dublin preparation contains four times that quantity of water.