Royle's manual of materia medica and therapeutics : including the preparations of the British pharmacopoeia and other approved medicines / by John Harley.

  • Harley, John, 1833-1921.
Date:
1876
Catalogue details

Licence: Public Domain Mark

Credit: Royle's manual of materia medica and therapeutics : including the preparations of the British pharmacopoeia and other approved medicines / by John Harley. Source: Wellcome Collection.

Provider: This material has been provided by King’s College London. The original may be consulted at King’s College London.

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    SOLUTION. Fig. 7. always maintain the same level, no matter how long the heat he applied or how rapid the ebullition, provided, of course, the trickle of water he continuous, and this is easily effected, as a compara- tively small quantity is required to supply the place of that lost hy evaporation. Wlien a higher degree of heat is required, as in the preparation of the hydragyri pxydum ruhrum, the naked flame may be used (fig. 6). 4. The Expression op Veget- able Juices.—This is most eco- nomically effected hy means of a powerful hydraulic press, which completely removes the juice, re- ducing the vegetable tissue to a dry cake. The picked leaves or cleansed roots should he previ- ously crushed between rollers, or hy the more tedious ]U’ocess prescribed in the Pharmacopirn, viz., bruising in a stone mortar. Under a pressure of 100 tons, leaves yield according to their succulency, from 75 to 50 per cent, of their weight of juice. 5. Clarification or Despumation (despumo, to take off the scum), may be effected in the case of honey, for example, by heating and skimming; or if this be insufficient, by the addition of white of egg or isinglass; the former carries any floating particles to the top, when the fluid is heated, the latter forms a kind of descending strainer which carries the particles to the bottom; the impurity being separated in the one case by slamming, and in the other by decantation. 6. Solution.—Solubility is a most important property, for so long as a substance remains insoluble, it is usually inert; active properties, however, are frequently developed by reducing the substance to an impalpable powder. This is the case with mercury, platinum, &c. Solution is effected when the cohesion of the particles of the solid IS overcome by their adhesion for water, alcohol, ether, &c., and it is, of course, gveatly facilitated by conditions which destroy the force ot cohesion; these are pulverisation, agitation, and heat. A few substances the hydrates and carbonates of lime, baryta, magnesia— are abnormal with regard to temperature, being more soluble in cold water than in hot. Water is the general solvent for salts, alburn, gelatm, sugars, gums, and nitrogenised organic substances. Alcohol, aether, chloroform, and benzol, for a few haloid salts, the latty and resinous hydrocarbons, essential oHs, the active principles ol plants, and the alkaloids generally. Oil is a solvent for sulphur, phosphorus, camphor, and the essential oils. Glycerine is a power- lul solvent for many substances which are only moderately or not