Soap is used to a large extent in the manu facture of silk, woollen and cotton goods. In the preparation of woollen goods it is required at three stages : scouring of raw wool to remove the wool-grease, scouring the yarns and cloth after oiling, in fulling and milling. Soap is used for "de-gumming" raw silk, for cleansing silk arid cotton before and after dyeing, and in the dye-bath, as well as for calico printing. For all these purposes a potash-olive oil soap is to be preferred; on account of the expense, however, it is frequently replaced for cheaper goods by soda soaps, and by soaps made from kitchen grease, bone-fat, palm and ground-nut oils, etc. The absence of free caustic alkali is imperative for all purposes ; for de-gumming silk and for cleaning cotton slight alkalinity (due to free carbonate) is permissible. The soaps should be readily soluble and should not contain rosin, or maize or cottonseed oils, which contain sub stances that are liable to act as resists to the dyes. Ammonia soaps and soaps made from sulphonated oils have recently been introduced for wool scouring.
Disinfectant soaps are manufactured by the addition of disinfectants such as coal-tar phenols (e.g., car bolic acid), birch tar, borax, thymol, icthyol, mercury salts, etc., before framing or during the milling process. Lysol prepar ations consist of soap solutions containing cresol. Soap itself possesses a slight germicidal action and apparently enhances the disinfectant power of certain other substances such as thymol, etc. Heavily medicated soaps are used in the treatment of certain skin diseases, as also the metallic soaps of zinc, copper, mercury and lead. Two preparations of hard soap (sodium oleate) are used in medicine : (I) Emplastrum saponis, made with lead plas ter; (2) Pilula saponis composita, which contains one in five parts of opium. A preparation of the green soft olive oil soap, known as opodeldoc (Linamentum saponis) is a domestic remedy for stiffness and sprains. The chief use of hard soap is in enemata; it also forms the basis of many pills. Given in warm water it
forms a ready emetic in cases of poisoning.
Besides their use in pharmacy the soaps of the alkaline earths and heavy metals have extensive application in the arts. Lime soaps are the principal constituents of many lubricating greases; aluminium oleate is used as an "oil thickener" for paint and varnish oils and for waterproofing textiles and paper; dissolved in benzene it forms a paper varnish. The oleates and linoleates and rosinates of lead, cobalt and manganese are used extensively as "driers" for paints and oil varnishes.
of soap:—McBain, Colloid Chemistry of Soap; 3rd and 4th Reports on Colloid Chemistry of the British Association (H.M. Stationery Office, 1920-22) ; MacLennan, J. Soc. Chem. Ind. 42, 393T., 1923 (microscopic structure). General and Technological:—G. Martin, Modern Soap and Detergent Industry (1924 with bibliography) ; Simmons and Appleton, Handbook of Soap Manufacture (1908) ; J. Lewkowitsch, Chemical Technology of Oils, Fats and Waxes, vol. iii. (1923) ; L. L. Lamborn, Modern Soaps, Candles, and Glycerine (1906) ; W. H. Simmons, Soap (Pitman's Common Commodities of Commerce, 1917) (elementary) ; British Pharmaceutical Codex (pharmacy). (E. L.; G. H. W.)
the inner bark of Quillaja Saponaria, a large tree of the rose family (Rosaceae), which grows in Chile. Re duced to powder, it is employed as a substitute for soap, since it forms a lather with water, owing to the presence of a glucoside saponin, which has a marked surface tension action. The same, or a closely similar substance, is found in soapwort (Saponaria officinalis), in senega root (Polygala Senega) and in sarsaparilla. The saponins are poisonous, having a marked haemolytic (blood destroying) action. They (with few exceptions) have the general formula Cnif27,-8010, and by the action of dilute acids they are hydrolysed into sugars and sapogenins, which are usually inert pharmacologically.