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.

  • Thomson, Anthony Todd, 1778-1849.
Date:
1830
Catalogue details

Licence: Public Domain Mark

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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    the sides of the paper in the funnel, which will wash down to its bottom all the minute particles of solid matter lo¢ged on its sides. The concentrated acids and alkaline solutions act too power- fully on the materials commonly employed for filters, to be filtered in the ordinary way ; and, therefore, when it is required that they should be filtered, which is not often the case, they are passed through strata of siliceous matter arranged in a glass funnel, in the following manner :—An irregularly-shaped pebble is first dropped into the throat of the funnel; then a layer of pieces of quartz, or broken flint glass, is placed over it; and, lastly, a thick stratum of coarsely-powdered glass, or of well washed white sand, covers the whole. ‘The substance to be filtered is poured gently on the surface of the sand, and soon passes through it and the substrata, leaving the impurities behind. Expression is employed for obtaining the juice of fresh vege- tables, and the unctuous vegetable oils. The subject is first bruised or coarsely ground, then inclosed in a hair-cloth bag, and subjected to violent pressure between the plates of a screw press. ‘The bags should be nearly filled; and the pressure should be gentle at first, and gradually increased. Vegetables in general, intended to be expressed, should be perfectly fresh, and cleansed from all impurities; and should be submitted to the press as soon as they are bruised, as the bruising disposes them more readily to ferment: but subacid fruits yield more juice, and of a finer quality, when the bruised fruit is allowed to stand for some days in an earthern or a wooden vessel. It is necessary to peel cranges and lemons before pressing them, to prevent the essential oil which their rind contains from mixing with the juice; and to some vege- tables, which are not very juicy, the addition of a little water is requisite. For expressing the unctuous seeds, in order to obtain the oil, which they contain, iron plates are employed; and the bruised seeds should be previously exposed in a bag to the steam of boiling water. Despumation is employed to clarify fluids which are so thick and clammy as not to be able to penetrate through the sub- stances of which filters are made, without some previous pre- paration. For this purpose it is sometimes required only to heat the liquor, which then throws up a scum that is to be carefully removed; but more frequently it is necessary to clarify it with the white of egg. When the substance is not spirit- uous, as syrup, for example, the albumen which is mixed .with the fluid coagulates when it is boiled, and, entangling G 2