The new dispensatory : containing, I. The elements of pharmacy. II. The materia medica, or an account of the substances employed in medicine; with the virtues and uses of each article, so far as they are warranted by experience and observation. III. The preparations and compositions of the new London and Edinburgh pharmacopoeas; with some of the most celebrated foreign medicines; the most useful of those directed in the hospitals; sundry elegant extemporaneous forms, &c. digested in such a method as to compose a regular system of pharmacy; with remarks on their preparation and uses; the means of distinguishing adulterations; of performing the more difficult and dangerous processes with ease and safety, &c. : the whole interspersed with practical cautions and observations / by W. Lewis, M. B. F. R. S.

William Lewis

Date:: 1799

Credit: The new dispensatory : containing, I. The elements of pharmacy. II. The materia medica, or an account of the substances employed in medicine; with the virtues and uses of each article, so far as they are warranted by experience and observation. III. The preparations and compositions of the new London and Edinburgh pharmacopoeas; with some of the most celebrated foreign medicines; the most useful of those directed in the hospitals; sundry elegant extemporaneous forms, &c. digested in such a method as to compose a regular system of pharmacy; with remarks on their preparation and uses; the means of distinguishing adulterations; of performing the more difficult and dangerous processes with ease and safety, &c. : the whole interspersed with practical cautions and observations / by W. Lewis, M. B. F. R. S. Source: Wellcome Collection.

Provider: This material has been provided by University of Bristol Library. The original may be consulted at University of Bristol Library.

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$confulerablv impregnated with their flavour: by the admixture of fut^ar, ei' the yolk ofan egg, or alkaline falts, they are made to- tally tiiiloluble in water. Digefled with volatile alkalies, they un- dergo various changes of colour, and fome of the lefs odorous ac- quire confiderable degrees of fragrance ; vvhilfl: fixt alkalies univer- lally impair their odour. • In t!ie heat of boiling water, thefe oils totally exhale ; and on this principle they are commonly extracted from fubjecSts that contaia them ; for no other fluid, that naturally exifts in vegetables, is ex- halable bv that degree of hear, except the aqueous moifture, from which the greatell: part of the oil is eafily feparated. Some of tlielc oils arife with a much lefs heat, a heat little greater than that iu which water begins vifibly to evaporate. In their refolution by a burning heat, they difPcr little from exprefled oils. Effcntial oils, expofed for fome lime to a warm air, fufFer an- al- teration very different from that which the exprefled undergo. In- Itead of growing thin, rancid, and acrimonious, they gradually become thick, and at length harden info a folid brittle concrete ; with a remarkable diminution of their volatility, fragrancy, pun- gency, and warm ftimulating quality. In this ftate, they are found to confift of two kinds of matter; a fluid oil, volatile in the heat of boiling water, and nearly of the fame q\iality with the original oil; and of a grofler fubftance which remains behind, not exhSlable with- out a burning heat, or fuch a one as changes its nature, and refolves it into an acid, an empyreumatic oil, and a black coaJ. The admixture of a concentrated acid inftantiy produces, in eflen- tial oils, a change nearly fimilar to that vifhich time efFeds. In making thefe kinds of commixtures, the operator ought to -be on his guard : for when a flrong acid, particularly that of nitre (of whicli hereafter] is poured haftily into an effential oil, a great heat and ebul- lition enCue, and often an explofion happens, or the mixture burfls into flame. The union of exprelfed oils with acids is accoriipanied with much lefs conflidt. 4. Concrete effential Oil. Some vegetables, as rofes and elecainpane roots, inllead of a fluid effcntial oil, yield a ful)fi:ance poffeffing the fame general properties, but of a thick or febaceous confillcnce. This fubftance appears to be of as great volatility, and fubtility of parts, as the fluid oils: it equally cxhalfs in the heat of boiling water, and concretes upon the furtacc of the collected vapour. The total exhalation of this matter, and Its concreting again into its original confiftent ftate, without any fcparation of it into a fluid and a folid part, diftinguifties it from ef- fcntial oils that have been thickened or indurated by age or by acids. 5« Camp/wr. Camphor, is a folid concrete, obtained chiefly from the woody$

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