SOAP.

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the presence of a chloride is to be inferred. Potash may be recognisedby the before-mentioned tests for this base (p. 274), as well as by thedeliquescence of the suspected acetate.

Physiological Effects. —Acetate of soda operates on the body likeacetate of potash, but is probably somewhat milder in its action.

Uses. —It is rarely employed for medicinal purposes. It may, how-ever, be used as a substitute for acetate of potasii, over which it has theadvantage of not being deliquescent.

In pharmacy and the arts it is largely employed in the manufacture ofacetic acid (vide p. 221), and on this account has been introduced intothe Pharmacopoeia , as the officinal source of this acid.

Administration. —The dose of it, as a diuretic, is from a scruple totwo drachms.

Sa'po. — Soap.

History. —The Hebrew word borith, translated in our version of theBible (Jer. ii. 22, and Mai. iii. 2), soap, is, by most commentators sup-posed to refer to a plant, or to the alkaline ashes of some plant. Pliny ,who {Hist. Nat. xxviii.) mentions snap, says it is made of tallow and ashes,ascribes its invention to the -GaBa/and adds, that the Germans employedboth thick and liquid soap (hard and soft soap ?) In the excavationsmade at Pompeii , a complete soap-boiler’s shop was discovered, with thesoap still perfect, though it must have been manufactured for more than1700 years (Parkes, Chem. Essays, ii. 5, 2 nd . ed.)

Natural History. —Soap is always an artificial product, unless thespontaneous formation of adipocire, from dead animal matter, be consi-dered an exception to this statement. This substance appears, from theanalysis of Chevreul , to consist of a small quantity of ammonia, of potash,and lime united to much margaric acid, and a very little oleic acid.

Preparation. —The manufacture of soap varies according to the qua-lity of this substance intended to be produced.

The soaps employed in medicine are those which contain, as theirbase, potash, soda, ammonia, lime, or oxide of lead: the three first arecalled soluble —the two latter insoluble soaps. Of these five, two onlyrequire notice at present, viz. those which contain either soda or potash :and for an account of the three other soaps I must refer to the articlesLinimentum Ammonle (p. 176), Linimentum Calcis, and EhplastrumPlumbi.

1. Of Soda Soap ( sapo sodaicus: s. natrinus: s. durus: s. spissus ofPliny ?) The quality of this kind of soap varies according to the kind offatty or resinous matter used in its manufacture.

(«.) Olive oil soda soap (sapo ex olivte oleo et soda confectus, Ph. L.sapo durus , Ph . Dub. Sapo Hispanicus.) —This is made by boilingolive oil with a solution of caustic soda (prepared by the action of limeon barilla or some other impure carbonate of soda) till the soap separates,to promote which common salt is sometimes added. It is then sufferedto congeal, and afterwards remelted in water to remove any adheringalkali. When sufficiently cold it is run into frames (wooden troughswith moveable bottoms), and after it has acquired sufficient firmness, iscut into long cakes or bars by means of a wire. (For further details,consult Aikin’s Diet, of Chemistry, art. Soap.)

There are two varieties of olive oil soda soap—one white (sapo albus)