“Besides the olein contained in the free state, there is,” says Mr Kingzett, “present a body called lecithine of the formula C42H84NPO9.” Gobloy, Diakonow, Strecker, Thudicum, and Kingzett have studied this substance, and express its chemolysis as follows:—
| Lecithine. | Water. | Glycero-phosphoric acid. | ||
| C42H84NPO9 | - | 3H2O | = | C3H9PO6 |
| Choline. | Oleic acid. | Palmitic acid. | |||
| + | C5H15NO2 | + | C18H34O2 | + | C16H32O2. |
That is to say, bases have the power, by abstracting water, to split up lecithine into, among other products, oleic and palmitic acid; so that when eggs are used for soap-making this process actually occurs, the soda or potash employed being sufficient to effect the necessary decomposition, and the resulting soap being, therefore, the product from not only the olein, but from the fatty acids so formed.
Tessie du Mothay has proposed a method for the recovery of potash, soda, &c., from soap water, which is as follows:—He decomposes the soap water by calcium, barium, or magnesium carbonate, and then passes carbonic acid through the liquid. The bicarbonate form precipitates organic matter and other impurities, and these settle down. The solution is then evaporated or treated with baryta water, which precipitates the last portion of foreign matters, and leaves a solution of caustic alkali. At a particular stage of the process an acid is used in order to hasten the separation of the resinous substances, and, in certain cases, of the sulphides of sodium and calcium, or barium and calcium and ferric oxide, and then passes carbonic acid into the liquid. The precipitated
metallic substances carry down with them the humus-like substances present.
Var. The principal varieties of soap found in commerce are:—
Almond Soap (Sapo amygdalinus), made from almond oil and caustic soda, and chiefly used for the toilet.
The P. Codex gives the following formula for its preparation:—Solution of caustic soda (1·334), by weight, 10 oz.; oil of almonds, by weight, 21 oz.; add the lye to the oil in small portions, stirring frequently; leave the mixture for some days at a temperature of from 64° to 68° Fahr., stirring occasionally, and when it has acquired the consistence of a soft paste, put it into moulds until sufficiently solidified. It should be exposed to the air for one or two months before it is used.
Animal Soap. Sapo animalis, Curd soap (B. P.). A soap made with soda and a purified animal fat consisting principally of stearin (P. Cod.). Put 5 parts of beef marrow with 10 parts of water into a porcelain or silver basin, heat, and when melted add by portions, with constant stirring, 21⁄2 parts of liquor sodæ (1·33); when saponified, add 1 part of salt; stir, remove the soap from the surface, drain it, melt it with a gentle heat, and pour it into moulds.