OFFICIAL OPERATIONS. 447 to be percolated, if the percolate is to be measured, or of a tared bottle, if the percolate is to be weighed; and by raising or lowering this recipient, the rapidity of percolation may be increased or lessened as may be desirable, observing, however, that the rate of percolation, unless the quantity of material taken in operation is largely in excess of the pharmacopoeial quantities, shall not exceed the limit of ten to thirty drops in a minute. A layer of menstruum must constantly be maintained above the powder, so as to prevent the access of air to its interstices, until all has been added, or the requisite quantity of percolate obtained. This is conveniently accomplished, if the space above the powder will admit of it, by inverting a bottle containing the entire quantity of menstruum over the percolator in such a manner that its mouth may dip beneath the surface of the liquid, the bottle being of such shape that its shoulder will serve as a cover for the percolator. "When the dregs of a tincture, or similar preparation, are to be subjected to percolation, after maceration with all or with the greater portion of the menstruum, the liquid portion should be drained off as completely as possible, the solid portion packed in a percolator, as before described, and the liquid poured on, until all has passed from the surface, when immediately a sufficient quantity of the original menstruum should be poured on to displace the absorbed liquid, until the prescribed quantity has been obtained." Modification of the above Process. "Authority is given to employ, in the case of Fluid Extracts, where it may be applicable, the process of Repercolation, without change of the original menstruum." Testing is directed by the Pharmacopoeia in convenient cases, for the purpose of ascertaining the identity and purity of its preparations; and a List of Reagents used is given at the end of the book, which is divided into three parts,-(1) Articles used in Testing, (2) Test-solutions, (3) Volumetric Solutions. The analysis directed under the title of each preparation is frequently Qualitative, but often Quantitative, and of the latter both the Gravimetric and the Volumetric methods are used. Pharmacopoeial testing and volumetric analysis are necessary to the work of the practical pharmacist, and as the apparatus used is simple and the operations are those in the line of his daily work, he should be familiar therewith. On the other hand the proximate analysis of organic substances for their principles, and the ultimate analysis of the same bodies for their elements require a high degree of skill and long experience, and should be left to the professional chemist. The apparatus used in testing consists of graduated flasks and jars, burettes, pipettes, funnels, beakers, test-tubes, capsules, crucibles, reagent-bottles, etc. The metric system is directed for all analytical work, and the apparatus employed should be graduated accordingly. OFFICIAL PREPARATIONS. The pharmacopoeial preparations may be presented under various methods of classification, one of the simplest being that which divides them into liquids and solids, the former being subdivided into groups named after their principal bases, viz. : LIQUID PREPARATIONS. Aqueous, Waters, Solutions, Infusions, Decoctions, Syrups, Honeys, Mu- In the following descriptions of the pharmacopoeial groups the composition and dosage of the various preparations are omitted, as they are fully detailed in the section on Materia Medica, under the title in each case of the principal constituent. AQUEOUS PREPARATIONS. Aquæ, Waters,-are aqueous solutions of volatile substances, which may be either solids, liquids, or gases, dissolved either by solution in cold or hot water, by filtration through an absorbent powder, by percolation through cotton saturated with the substance, or by distillation. The official waters number 15, including the two forms of Aqua itself, as follows, viz.— Of the above-named two are made by simple solution (A. Amygdala Amaræ and A. Creasoti), three are made by passing gases through water (A. Ammonia, A. Ammoniæ Fortior, and A. Chlori), three are made by distillation (A. Aurantii Florum, OFFICIAL PREPARATIONS. 449 A. Destillata and A. Rosa), and the other six are made by percolation through cotton impregnated with the substance. All waters deteriorate when long kept, microscopic plants being propagated in them from spores from the atmosphere. They should be prepared only in such quantities as are needed for use within a reasonable time. Liquores, Solutions,-comprise all aqueous solutions of nonvolatile substances except the syrups, infusions and decoctions, which naturally form distinctive classes. Included among the Liquores is the Solution of Gutta-percha, the solvent of which is Chloroform; all the others being made with water. There are 28 official solutions, as follows, the first 11 being simple aqueous solutions; the next 16 being chemical aqueous solutions, in which the properties of the dissolved substance are altered by chemical action; and the last-named being a solution in Chloroform. Syrupi, Syrups,-are concentrated solutions of Sugar in Water or in aqueous liquids. They sometimes contain Acetic Acid, and occasionally Alcohol; and are termed simple, medicated or flavored, according as they are simple solutions of sugar in water alone, or contain soluble medicinal substances, or flavoring ingredients. The Sugar used should be very dry, and its official description corresponds with the granulated sugar of commerce. The permanency of these preparations chiefly depends on their possessing the proper relative proportions of sugar and water. They are prepared either by solution with heat, by agitation without heat, by adding a medicated liquid to simple syrup, by digestion or maceration, or by cold percolation; these processes being all officially directed except the last. They are best preserved by being poured while hot into pint bottles, which should be corked securely while full, and the tops dipped into melted sealing-wax. Fermented syrups are useless for dispensing purposes. The number of official syrups is 34, as follows, viz.— Mellita, Honeys,-differ from syrups merely in their being prepared with honey as a base. The Oxymel and Oxymel Scilla of the B. P. are similar preparations, containing also Acetic Acid. There are 3 official Honeys, including two forms of honey itself, viz. Mel. Mel Despumatum. Mel Rosa. Mucilagines, Mucilages,—are thick, viscid liquids, prepared by dissolving gum in water, or by extracting with water the mucilaginous principles from certain plants. They are easily spoiled and should be kept only in small quantities. The official Mucilages number 5, as follows, the three first-named being prepared without heat, the two last-named with heat, viz.— Mucilago Acacia. Mucilago Sassafras Medullæ. Mucilago Ulmi. Misturæ, Mixtures,-in official pharmacy are aqueous preparations of insoluble substances held in suspension by a suitable vehicle. In extemporaneous pharmacy the term mixture has a wider signification, as explained under that head. They are generally prepared extemporaneously upon prescriptions, as few of them are of the stability necessary to insure their preservation beyond a few days. The official Mixtures number 11, of which OFFICIAL PREPARATIONS. 451 one (Mistura Ferri et Ammonii Acetatis) is misnamed, and should be entitled a Solution, as it does not contain any insoluble substance. Their names are as follows, viz.— Mistura Ammoniaci. Mistura Amygdalæ. Mistura Chloroformi. Mistura Ferri Composita. Mistura Glycyrrhiza Composita. Mistura Potassii Citratis. Of the above-named, the first two are simple gum-resin emulsions, the third is a seed-emulsion, the fourth an egg-emulsion: the next four contain insoluble powders in suspension by the aid of gum arabic, sugar, etc., the next two do not contain insoluble powders in suspension, while the last is an effervescing mixture. Infusa, Infusions,-are prepared by treating vegetable substances with hot or cold water without boiling. Cold water is preferred when the drug contains a desirable volatile principle, or when its active ingredient is injured by heat. The drug should be coarsely comminuted, sliced or bruised, and treated by maceration or percolation with the proper quantity of water, which in the absence of specific directions to the contrary should be to parts by weight to 1 of the drug. These preparations should be freshly made when required, as they are very prone to decomposition. The number of official Infusions is 5, viz.— Infusum Brayeræ. Infusum Digitalis. Infusum Sennæ Compositum. The proportions of drug to menstruum in the official infusions vary from 11⁄2 per cent. in the case of Digitalis to 4 per cent. in the case of Wild Cherry and 6 per cent. in the cases of the others. Alcohol is an ingredient of the Infusion of Digitalis to prevent decomposition. Many dispensing pharmaceutists are in the habit of making infusions from concentrated alcoholic tinctures or from fluid extracts. It is a very reprehensible practice, especially in those cases where the active ingredients are of a resinous nature and therefore precipitated when the alcoholic solution is added to water. Decocta, Decoctions,-are made by boiling vegetable substances with water. As very few drugs contain active ingredients which are not injured by heat, these preparations have never |