A dispensatory, or commentary on the pharmacopoeias of Great Britain. Comprising the natural history, description, chemistry, pharmacy, actions, uses, and doses of the articles of the materia medica / by Robert Christison.

  • Christison, Robert, Sir, 1797-1882.
Date:
1842
Catalogue details

Licence: Public Domain Mark

Credit: A dispensatory, or commentary on the pharmacopoeias of Great Britain. Comprising the natural history, description, chemistry, pharmacy, actions, uses, and doses of the articles of the materia medica / by Robert Christison. Source: Wellcome Collection.

    17/1038 (page 5)
    INTRODUCTION.— Decocitons. . Vv as its sassafras is concerned,—the Decoctum sarz@ compositum, on account of the same ingredient,—the Decoctum hematoxyli, in re- ference tothe cinnamon added to it,—the Decoctum scopari compo- situm, in reference to the juniper-tops; and the Decoctum sarze of - the three Pharmacopeeias is considered by good authorities to be similarly circumstanced. In other cases during ebullition import- ant chemical reactions take place, in consequence of which the ac- tive constituents are either rendered insoluble, or undergo decom- position. Cinchona-bark for example cannot. be boiled in water sufficiently for the extraction of its active principles, cimchonia and quina, without these alkaloids combining with the red colouring principle of the bark, and forming a compound sparingly soluble at 212° and almost insoluble at 60°. In making Decoction of aloes protracted ebullition is unadvisable, because the soluble active -principle, aloésin, undergoes oxidation, and passes to the state of insoluble, inert resinoid matter. In the case of Senega-root, a decoction cannot be made without the active principle, Senegin, forming an insoluble compound with the colouring matter and al- bumen of the root; so that this preparation ought to be abandoned, as the Edinburgh College has recently done, in favour of an infu- sion. In other instances again the effect of a boiling temperature is to enable the water to dissolve out principles injurious to the quality of the preparation. Of this result an excellent illustration is Calumba-root, which contains, besides an active bitter principle easily soluble in cold water, a large quantity of starch, which can- not be dissolved except at a temperature near that of ebullition, and which ought to be left behind if possible, because it renders the solution mucilaginous and apt to become speedily mouldy. The process of boiling is the less necessary, that in general the same proportion of water exhausts vegetable substances equally well at 60° in the way of percolation, as at 212° in the way of de- coction, and often more completely. ‘There are important excep- tions however. For nux-vomica is with difficulty exhausted by cold water in any mode, while it is more readily exhausted by the method of decoction. And all the emulsive preparations which depend for their properties upon starch or certain forms of the gummy principle, require ebullition ; for otherwise the emulsive principles are not dissolved at all. Decoctions should be prepared in vessels so far covered as to pre- clude a free circulation of air, while they allow the escape of steam. The process should be continued for as short a period as suffices for the due extraction of the active materials of the drug. And subsequent concentration by prolonged boiling should for the most part be avoided. The vessels used for preparing decoctions are best made of glass or earthen-ware; but on the large scale clean cast-iron pots, or vessels of copper, brass, or tinned-iron are often admissible. Copper vessels are frequently to be avoided because vegetable decoctions corrode them, and may become dangerously