The London dispensatory, containing: I, the elements of pharmacy; II, the botanical description ... and medicinal properties, of the substances of the materia medica; III, the pharmaceutical preparations and compositions of the pharmacopoeias of the London, Edinburgh, and Dublin Colleges of Physicians / By Anthony Todd Thomson.

Anthony Todd Thomson

Date:: 1836

Credit: The London dispensatory, containing: I, the elements of pharmacy; II, the botanical description ... and medicinal properties, of the substances of the materia medica; III, the pharmaceutical preparations and compositions of the pharmacopoeias of the London, Edinburgh, and Dublin Colleges of Physicians / By Anthony Todd Thomson. Source: Wellcome Collection.

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sisting of the combination of substances, with a view either of obtaining compounds by their direct chymical union, or the products of chymical action resulting from their mutual de- composition. —— EEE Secrion III. PHARMACEUTICAL OPERATIONS AND APPARATUS. THE operations of pharmacy may be arranged under two classes : — I. Operations which are purely mechanical. I]. Operations which are performed by chymical powers } and agents. The first are intended for determining the weight and bulk of bodies, diminishing their cohesion, and separating their integral parts: the second are intended for separating the elements of bodies from one another, and for re-uniting these elements into new combinations. J. PHARMACEUTICAL OPERATIONS PURELY MECHANICAL. a. Of the means of determining the weight and bulk of bodies. In pharmaceutical processes it is essential that the quantities of the substances employed be accurately ascertained; and for this purpose, beams with scales and measures must be provided. Several sets of beams and scales are necessary; one set for large weights, from one pound to one hundred weight or more ; another for weights not exceeding five pounds; and a third for small weights under two drachms. A good beam should re- main in equilibrium, both by itself, and when the scales are suspended to each extremity; the largest sets should be exact to within half a drachm; the second should be sensibly affected by two or three grains at most; and the smallest by the hun- dredth part of a grain. Apothecaries, however, seldom have beams of such accuracy, and, generally, those that they em- ploy are much injured by exposure to acid fumes, and from want of cleanliness. ‘To preserve the delicacy of beams, they should be kept in very close cases, and not left suspended longer than is absolutely necessary; nor should they be over- loaded. Drugs are bought in the gross by avozrdupors weight, which is the standard of most articles of merchandise; but, for the composition of medicines, ¢roy weight is directed to be used by the British Colleges. The following TaBix exhibits the

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