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Washing

This is resorted to in chemistry for two widely different purposes.

When a substance contains both soluble and insoluble matter, the soluble portion can be separated from the insoluble by washing; this is called Lixiviation. (See No. 23.) When it is desired to cleanse or remove impurities from an insoluble powder, this is also effected by washing. (See Nos. 14 and 3841.) ized, as-"boil to a pint, and strain," the latter method being generally employed for those substances that do not suffer by lengthened boiling. Distilled water, or perfectly clean rain water, should alone be used for decoctions.

Spring and river water, from their containing lime, have less solvent powers.

Decoctions of all vegetables not exerting a very powerful action on the human system may be made by boiling 1 ounce of the vegetable matter in 1 pint of water for 10 or 15 minutes. The ordinary dose of such a decoction is the same as that of a similar infusion. (See No. 37.) When the medicinal properties of vegetables are volatile, or are injured by a strong heat, infusion should be had recourse to, in preference to boiling; but when a solution of the fixed constituents is alone sought, decoction Preparations. The following is preferable. In preparing compound decoctions, those ingredients should be boiled first which least readily impart their active princimethods of preparing decoctions, extracts, tinctures, &c., are from the best practical sources. Other directions for making ples, and those which most readily impart extracts, essences, attars, &c., for the special them should be added afterwards. In many purposes of Perfumery, &c., will be found cases it will be proper simply to infuse the under their respective headings. more aromatic substances in the hot decoction of the other ingredients, by which means their volatile principles will be preserved.