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SOAP , a chemical See also:compound or mixture of chemical compounds resulting from the interaction of fatty See also:oils and fats with alkalis. In a scientific See also:definition the compounds of fatty acids with basic metallic oxides, See also:lime, See also:magnesia, See also:lead See also:oxide, &c., should also be included under soap; but, as these compounds are insoluble in See also:water, while the very essence of a soap in its See also:industrial relations is solubility, it is better to speak of the insoluble compounds as " plasters, " limiting the name " soap " as the compounds of fatty acids with soda and potash. Soap both as a medicinal and as a cleansing See also:agent was known to See also:Pliny (H.N. See also:xxviii. 51), who speaks of two kinds—hard and soft—as used by the Germans. He mentions it as originally a Gallic invention for giving a See also:bright See also:hue to the See also:hair (" rutilandis capillis "). There is See also:reason to believe that soap came to the See also:Romans from See also:Germany, and that the detergents in use in earlier times and mentioned as soap in the Old Testament (Jer. ii. 22; Mal. iii. 2, &c.) refer to the ashes of See also:plants and other such purifying agents (comp. vol. x. P. 697). Soap appears to have been first made from See also:goat's See also:tallow and See also:beech ash; in the 13th See also:century the manufacture was established at See also:Marseilles from See also:olive oil, and in See also:England during the next century. The processes and extent of the manufacture were revolutionized at about the beginning of the 19th century by See also:Chevreul's classical investigations on the fats and oils, and by Leblanc's See also:process for the manufacture of See also:caustic soda from See also:common See also:salt. Previous to Chevreul's researches on the fats (1811–1823) it was believed that soap consisted simply of a binary compound of See also:fat and See also:alkali. See also:Claude J. See also:Geoffroy in 1741 pointed out that the fat or oil recovered from a soap See also:solution by neutralization with a See also:mineral See also:acid differs from the See also:original fatty substance by dissolving readily in See also:alcohol, which is not the See also:case with See also:ordinary fats and oils. The significance of this observation was overlooked; and equally unheeded was a not less important See also:discovery by See also:Scheele in 1783. In preparing lead See also:plaster by boiling olive oil with oxide of lead and a little water—a process palpably analogous to that of the soap-boilerhe obtained a sweet substance which, called by himself " Olsiiss " (" principium dulce bleorum "), is now known as " See also:glycerin." These discoveries of Geoff See also:roy and Scheele formed the basis of Chevreul's researches by which he established the constitution of oils and the true nature of soap. In the See also:article OILS it is pointed out that all fatty oils and fats are mixtures of glycerides, that is, of bodies related to the alcohol glycerin C,H6(OH)3, and some fatty acid such as palmitic acid (C16H31O2)H. Additional information and CommentsThere are no comments yet for this article.
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