({rommedica?nentum,medicine,) pharmacy, is the art of making and preparing medicines, sometimes of preparing poison. Pharmacy hath been distinguished into chemical and galenical. The first consists of those operations in which fire was the chief medium, for the purpose of separating different ingredients of a compound, or combining different substances into one form; each supposed to differ in qualities from the body which afforded them, or from the substances thus combined. The second consisted in altering the form or texture of simples, so as to render them fit to be taken, or applied, without attempting any change in their qualities; and in uniting them in compositions of various forms, where each simple was supposed to retain its original properties. But these distinctions have been long neglected.

The operations in pharmacy may be reduced to these four kinds:

1. Commensuration, or the adjustment of quantities, necessary for the due administration of simple and compound medicines, as well as for the formation of those very compounds.

2. Change of form, or texture, often requisite, both for the convenient administering of simples, and forming compounds. The instances in which this is practised are for the reduction of solid cohering bodies to powder, and of those that partake both of solid and fluid into pulp; for converting salts, and other soluble bodies to fluidity; and, in other cases, the restoring them when fluid to their solid state. The several particular operations by which these changes are produced have been styled trituration, calcination, solution, exsiccation, and crystallization.

3. Extraction or separation, in a general sense, not confined to the making extracts of the gums and resins of vegetables. The different elements of many compound bodies having qualities and powers, when separate and pure, which they are incapable of exerting when their force is suppressed by the quantity or counteracted by the repugnant qualities of the other component parts, are by this means obtained, as acid spirits, testaceous earths, etc.

4. Composition is either simple mixture or chemical combination. In the first the different species are intended to act, each according to its own nature, without producing any mutual change of, or alteration in, each other. But this is the less important kind of composition, as single simples will often answer the end of such composition. The second produces many efficacious remedies, which have no adequate substitutes obtained by other means; as the preparations of quicksilver, antimony, saline substances, etc. in which a new compound is produced, differing in its nature and efficacy from any of its component parts.

To execute these several intentions, a variety of methods and proper instruments are employed; hence the terms calcination, crystallization, corrosion, depuration, digestion, distillation, expression, exsiccation, fermentation, fusion, incorporation, precipitation, pulverization, solution, sublimation, etc.

The means of effecting pharmaceutic operations are of two kinds, viz. chemical and mechanical. By chemical are meant the natural media by which bodies can act on, and produce a change in, each other, not explicable from the known general properties of matter, or laws of motion. By mechanical, artificial instruments. For brevity sake in speaking of these two kinds, the first is called media, the latter instruments. See Pharmacia.

Medicamenta extemporanea, (from medico, to heal). Magistralia, compositions prescribed by the physician, according to the circumstances of the patient, and made up for this purpose only. A variety of these are found in some Pharmacopoeias, under the title of extemporaneous medicines, and all the compounds of practice chiefly consist of them. These are the resources of ignorance and idleness; with these the fashionable practitioner provides himself, and prescribes to the name of a disease, with little knowledge of its nature or that of the remedy. To discountenance such impositions on a credulous public, who contentedly employ every one who calls himself a physician, we have seldom added formula?, and shall not insert any, unless stronger reasons than at present occur to us should be offered. See Formitae.