vapour, to pass into close vessels, in which such goods are suspended.
Soap is one of the most valuable articles in domestic economy: its uses in various manufactures require no description. The ashes, refuse, or waste, remaining after this compound is made, furnish an excellent manure. (See vol. i. p. 27.) The suds, or water, in which soap has been dissolved, are of great service to gardeners; as they effectually destroy insects in hot-houses. (See also vol. ii. p. 496, and vol. iii. p. 232.) Farther, it appears from a patent granted, in June, 1780, to Mr. Samuel Unwin, and which is now expired; that soap-suds, after being used in scowering, washing, &c. may be rendered sufficiently strong to serve the same purposes, repeatedly, and even for the re-production of soap. He directs any quantity of the suds (when rendered useless by the foul or greasy matters they may hold in solution) to be boiled over a brisk fire; in consequence of which, a scum of grease, oil, &c. will rise to the surface. This must be saturated or dissolved, by the gradual addition of pot-ash, or similar alkaline salt; the whole being stirred, till the scum disappear. The soap-suds, thus corrected, are now to boil for two hours, when the fire must be discontinued, in order that all feculent or earthy particles may subside. The liquor will then be found sufficiently purified, and may again be employed for scowering, &c. every time repeating the process before described. In order to make soap of such rectified suds, the patentee directs any quantity to be drawn off into shallow vessels, in which it must be evaporated over the fire, till it acquire a due consistence; and, by adding the usual proportion of sea-salt, the mixture will become hard, and possess all the properties of saponaceous matter.
Soap is also of considerable utility in medicine: for this purpose, however, it is prepared without the aid of heat; the ley being filtred and concentrated by evaporation, to such a degree, that a phial capable of holding an ounce of water, will contain one ounce and 216 grains, or nearly 112 oz. of such lixivium. One part of the latter is then mixed with two parts of the oil of sweet-almonds, or of olives, in a stone vessel; the ingredients are occasionally stirred; and, in the course of a week, a firm white soap will be obtained.—This compound is reputed for its efficacy in dispelling calculi, or stones, in the human body; and, when dissolved in ale, it has with advantage been administered in the jaundice. Boerhaave always prescribed it with resinous pills; as it contributes to decompose them in the stomach. But, of late years, soap has fallen into disrepute, and is now seldom employed in medicine; though we are informed by M. Bellot, that soap-water has been given, with the happiest effects, to persons bitten by mad animals.
There are numerous vegetables, that may afford proper substitutes for soap, in its various applications to domestic uses; but, as many of these have already been pointed out; and others will occur in the subsequent pages; we refer the reader to our General Index of Reference.
SOAP-EARTH, or Steatites, L. a species of fossil, which abounds in Devonshire, Cornwall, and the islands in the vicinity of the Lizard Point. It is generally of a white,
