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The Edinburgh new Dispensatory : containing 1. The Elements of pharmaceutical Chemistry ; 2. The Materia Medica; or the natural, pharmaceutical and medical History, or the Substances employed in Medicine ; 3. The pharmaceutical Preparations and Compositions ; including Translations of the Edinburgh Pharmacopoeia published in 1805, of the Dublin Pharmacopoeia in 1807, and of the London Pharmacopoeia in 1815
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Sect. 2. Pharmaceutical Operations.

Ixxxi

from insects, must be kept in well-covered glasses. Fruits andoily seeds, which are apt to become rancid, must be kept in acool and dry, but by no means in a warm or moist place.

369. Oily seeds, odorous plants, and those containing vola-tile principles, should be collected fresh every year ; others,whose properties are more permanent, and not subject to de-cay, will keep for several years.

370. Vegetables collected in a moist and rainy season, arein general watery, and apt to spoil. In a dry season, on thecontrary, they contain more oily and resinous particles, aremore active, and keep much better.

MECHANICAL OPERATIONS OE PHARMACY.

a. The determination of the weight and bulk of bodies.

b. The division of bodies into more minute particles.

c. The separation of their integrant parts by mechanicalmeans.

rl. Their mixture, when not attended by any chemicalaction.

WEIGHTS AND MEASURES.

371. The quantities of substances employed in pharmaceu-tical operations are most accurately determined by the processcalled weighing. For this purpose, there should be sets ofbeams and scales of different sizes ; and it would be advisableto have a double set, one for ordinary use, and another for oc-casions when greater accuracy is necessary. A good beamshould remain in equilibrium both by itself and when the scalesare suspended, one to either end indifferently ; and it shouldturn sensibly with a very small proportion of the weight withwhich it is loaded. Balances should be defended as much aspossible from acid and other corrosive vapours, and shouldnot be overloaded, or left suspended longer than is necessary,as their delicacy is thereby very much impaired. It is unfortu-nately not unnecessary to mention, that the scales and weights,as well as measures, funnels, mortars, &c. should be kept ex-tremely clean. Some nice apothecaries have their scales madeof glass, ivory, or tortoise shell; but in many shops the commonbrass scales are disgustingly filthy, and covered with verdigris.

372. The want of uniformity of weights and measures is at-tended with many inconveniences. In this country, druggistsand grocers sell by avoirdupois weight; and the apothecaries

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