Note-book of materia medica, pharmacology and therapeutics / by R.E. Scoresby-Jackson.

  • Robert Scoresby Jackson
Date:
1895
Catalogue details

Licence: Public Domain Mark

Credit: Note-book of materia medica, pharmacology and therapeutics / by R.E. Scoresby-Jackson. Source: Wellcome Collection.

    30/864 page 34
    Tlie following—in alphabetical order—are the principal pharma- ceutical processes, but including only such as are not commonly treated of in courses of lectures on chemistry :— Clarification.—The removal of substances which impair the trans- parency of liquids. Heat is commonly employed for this purpose, as in the clarification of honey; the honey is melted in a water-bath, whereby the impurities are set at liberty, and may be either removed by subsidence, or by skimming, according to their density, or by filtration. But clarification is more commonly effected by means of albumen with the subsequent application of heat. White of egg is used for this purpose : it is first mixed with a little water and then added to the cold liquid, care being taken to diffuse it equally through the liquid before the application of heat. The temperature of the mixture is then gradually raised until the albumen coagulates, in doing which it seizes the impurities su.spended in the liquid, and either floats or subsides with them according to their combined density, as compared with that of the fluid. Comminution.—The process by which vegetable substances are broken into coarse pieces, as in the preparation of infusions and decoctions. This operation is effected by means of the cutting, slicing, rolling, or cradle-knife, when the substance is easily cut; but if it be dense and hard, as wood, roots, barks, &c., as a prepara- tory operation to powdering the chopping-trough is more suitable. Contusion.—The process for powdering hard and tough substances. It is effected by means of the pestle and mortar, handworked if the quantity to be operated upon be small, but if large, the pestle is worked by machinery. Crushing is an operation performed upon recent herbs to obtain their juices for various purposes. This process is sometimes effected by means of a pestle and mortar; but when the substance is in large quantity, it can only be accomplished by the aid of a drug ox pugging mill. Crystallisation.—Many medicinal substances are directed to be kept in the crystalline form. It is the state in which they are least subject to adulteration; and the crystal is one of the chief charac- ters by which we recognise them. Crystals are beautifully regular mathematical forms assumed by certain substances in their passage from a gaseous or liquid to a solid state. They are sometimes obtained from volatile substances by sublimation or by fusion; but far more commonly either by the gradual evaporation of the fluid in which the substances are dissolved, or by some chemical interference forming a new substance which the solvent is no longer capable of
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