SOAP, is a peculiar chemical compound of animal or vegetable oils and fats, with the alkalies. The use of soap does not date from a very early period; although mentioned in the Bible there is much reason to believe that alkali used in washing is meant, and not manufactured soap. It appears to have originated in Germany, and was introduced to the Romans about the beginning of the Christian era. At first its use seems to have been greatly misunderstood, for Pliny says, "Soap, too, is very useful for this purpose" (the dispersion of scrofulous sores), "an invention of the Gauls for giving a reddish tint to the hair. This substance is prepared from tallow and ashes, the best ashes for the purpose being those of the beech and yoke
elm; there are two kinds of it, the hard soap and the liquid, both of these used by the people of Germany, the men in particular more than the women." It is more than probable that Pliny was mistaken in the motive of the Gauls for washing their heads with soap, and that the reason was cleanliness, which of course brightened the naturally light colour of their hair.
The aborigines of South America manufacture a kind of hard soap in a very peculiar manner; but whence they derived the art, or how long they have used it, is not known. They select a tree, which in the neighbourhood of Para is called Chereuba; this is cut down and burned to ashes, which are mixed with lime and Carapa oil, made from the large seeds of Carapa Guianensis, and, boiled, it is poured off from the ashes whilst liquid, and hardens on cooling. This soap is much used by the washerwomen in many parts of Brazil.
Many plants are found to have detergent properties similar to soap, and in the countries producing them are employed for washing. Thus, in the West Indies and tropical America, the berries of the soap-tree (Sapindus saponaria), are much used, and are found to be very far superior in cleansing power to common soap. Another South American tree, the Quillaia saponaria, and perhaps other species of the same genus, yields a bark which has very powerful saponaceous qualities, and is not only used extensively in its native country, but has recently been introduced experimentally to this country, several importations having been received at Liverpool, for making a saponaceous solution for washing woollens. It is at least equal if not superior in strength to our best yellow soap. Where known, it is esteemed for washing the hair.
The natives of the Malayan Islands use the bark of the Gogo-tree (Entada purshata) for the same purposes, and this bark is highly prized by the ladies of Manila for cleansing and brightening their beautiful tresses. Various other vegetable productions are used, but less extensively. The process of saponification is much varied, and considerable difference also exists in the oleaginous materials, consequently we find numerous kinds of soap in use for different purposes. The ordinary process consists in submitting oleaginous or fatty matters to the chemical action of alkaline lyes, and boiling the compound to get rid of a portion of the water used for the solution of the alkali. They may be arranged under the following heads—Hard, Soft, and Medicated Soaps, each of which comprises numerous varieties.