A universal formulary : containing the methods of preparing and administering officinal and other medicines. / by R. Eglesfeld Griffith.

  • Robert Eglesfeld Griffith
Date:
1851
Catalogue details

Licence: Public Domain Mark

Credit: A universal formulary : containing the methods of preparing and administering officinal and other medicines. / by R. Eglesfeld Griffith. Source: Wellcome Collection.

Provider: This material has been provided by Royal College of Physicians, London. The original may be consulted at Royal College of Physicians, London.

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    V OFFICINAL PREPARATIONS AND DIRECTIONS. 457 —»— rue, and the undeveloped corolla of the clove-tree, oils may be squeezed out by pres- sure with the nail. In some rare instances, as in that of the Liquid Borneo-Camphor from the Dri/ohahnops Camphora, and that of the Laurel-oil of Guiana from a species of Ocotea, volatile oil is obtained largely, and of considerable purity, by exudation from incisions. Much more frequently, however, it is exuded spontaneously, or from incl- usions, as a turpentine in combination with resin, or as a gum-resin in union with both |gum and resin. Most frequently of all, it cannot be obtained by any of these modes, tbut adheres with more or less force to the flowers, leaves, fruit, bark, or wood, which ccoptam It. In that case, it is sometimes destroyed or dispersed when the plant is ddried, more especially if the organ which contains it is the flower; but often, when coontained in the leaf, and very generally, if contained in the seed, bark, or wood, it is rretained m part, or altogether, under desiccation, and even under long keeping. In ssome instances, it appears that the volatile oil obtained from plants does not exist rceady formed, but is produced, on bruising or distilling them with water, throuah ilhe reaction of other principles on one another. Of this mode of production, two rremarkable examples exist—the volatile oils of the bitter almond and black mus- bfcard seed; and it is probable that the oils of cherry-laurel leaves, peach leaves, and ODt the leaves of other amygdalaceous plants, are similarly circumstanced. A few volatile oils used in medicine are obtained by expression, such as the oils of )Drange, lemon, and bergamot, already mentioned. When oils exude along with resin m the form of turpentme, they may be separated from the resin by heat alone, as they are volatilizable at about the temperature of 400°. But thus obtained, they cannot I? n 3^^*^' because the heat required is too near that at which resins, as well as • n I themselves, undergo decomposition. In general, therefore, this plan is not oonowed, tor pharmaceutic purposes; and volatile oils are obtained from turpentines by blistillmg them with water. For, although they do not enter into ebullition at the teemperature of boihng water, their vapors pass over in large quantity with steam; and, Condensing along with it, form distilled waters—with volatile oils either floating on me water, or, more rarely, sinking to the bottom. The volatile oils of many vegetable ibstancesare to be separated in this way alone, because the other principles, con- med along with them in the crude substances, are empyreumatized by the higher iemperature which is required to disengage the oil without the co-operation of watery rapor. In some instances, it has been thought advantageous to substitute for water a the still a strong solution of common salt, because a somewhat higher tempera- ore IS required to boil it. There seems an advantage, in this change, for the rectifica- iQon ot oils previously obtained from the raw materials in which they reside; but the ildvantage m the case of distillation from crude vegetable substances is doubtful. L . ^ 5^^*.^?^ 0^ distilling volatile oils difl-ers little from that described above for pre- ^nng distilled waters. The same precautions must be observed in applying heat, and tor the same reasons The formation of mucilaginous matter at the expense of the oil j»owards the close of the distillation, is shown by the globules of oil coming ove^ jahQveloped m a fine pellicle of it. The quantity of water must be proportionally less ]l|rr, rather, the same portion of water is to be used with successive portions of the laaterial which yields the oil; otherwise, a material loss is sustained by solution of we oil in the water. In some instances, where the oil exists in low proportion, and is . great value, the distiUed fluid should be left at rest for some time, and exposed to } low a temperature as can be commanded. The mixed vapors which pass over condense into a milky-looking fluid, which, after kanding some time m the receiver, separates into two portions, one a solution of apart : oil m water and the other of the oil itself, which occupies the upper or lower part Jcordmg as it is lighter or heavier than the water. ^ ' Chevalher gives the following rules for the distillation of volatile oils :— Hter quaUty''^ ''^'^'^ ^'^^ quantities, in order to obtain a greater product, and of 2. To conduct the distillation rapidly. 3. To divide the substances minutely, in order to facilitate the extrication of 'iG Oil* 4. To employ only sufficient water to prevent the plant from burning.