SOAP. _1. chemical compound of fat or oil, animal or vegetable, with potash or soda. Various plants were used in ancient times for their cleansing qualities, among others, the juice of a plant called Struthinne by the Romans. Pliny asciilies the invention of soap to the Gauls and credits the ancient Germans with making both hard and soft soap. Among plants known to the moderns for their saponaceous and deter gent and cleansing qualities, are the berries of the soap tree, Sapindus saponaria; the bark of the Qnillaia saponuriu, both natives of South America. The juice of aria officinalis, Bouncing Bet, has long been used in England, for cleansing dresses. In California, the bul bous root of Pliellavium pomariclianum has been extensively used in the place of soap for washing clothes, since the settleinent of the country. Of the two alkalies employed for making soap, soda is used for hard soap and potash for soft Qoap. The more solid fats, as tallow and suet, make firmer soaps than the soft fats which con tain more oleic acid. In connection with pot ash, the soap fats make a still softer and watery soap. To harden these a small quantity of fused crystals of sulphate of soda are used. So if the soap is too hard rape or linseed oil, or rosin combined with the tallow will soften the pro duct. Lard and soda make a very hard, white, and excellent toilet soap. C'astile soap is made with olive oil and soda, and the peculiar marbled appearance is given it, the dark by stirring into it a solution of sulphate of iron, which, on and near the outside of thc bars, by being oxygen ated by the air, gradually assumes a reddish appearance; the streaks and patches are pro duced by the black oxide separating from the water after being stirred in the soap when in a semi-fluid state. Other colors and marblings are given this and other fancy soaps, by rubbing up vermilion or ultramarine olive oil in soap. A small portion is taken up with a spatula or thin knife and worked into the mass of melted soap and stirred about until the proper effect is pro duced. So turmeric is also employed for col oring, or any innocent coloring matter may be employed. Transparent soap is made from the hardest fats and soda The soap is then dis solved in alcohol, filtered and evaporated to the proper consistency. Soap balls are made by dis solving soap in a very little water, and then working into balls with starch. The cleansing and detersive qualities of soap may be increased by the addition of ammonia, camphor, spirits of turpentine, perfumes being added to disguise the smell of the chemicals. Soap varies in its quality according to its power of taking up water in the making. Castile soap should not contain more than fourteen to fifteen per cent. of water. The soaps made of cocoanut oil often contain nearly seventy-five per cent. of water. Ordinary soft soap contains nearly forty-eight per cent. of water, while the ordinary hard washing soaps contain from thirty-five to twenty-three per cent. of water, according to quality,. The proportions of fat and alkali in making soft soap, is, for 450 pounds, 200 pounds of clean fat or oil, and 72 pounds of potash in lyes of specific gravity 1.110. Lye that will just bear out an egg is called weak lye, and if it bears out au egg buoyantly or of the size of a shilling piece, it is called strong lye. When of the proper consistency of soft soap, or when it forms a half solid, jelly-like substance, when cold, it may be converted into hard soap, by- adding two pounds of salt, in the form of strong brine, to each pound of fat or oil used.
Add the solution of salt gradually into the boil ing mass, stir, and the sodium of the salt will takc the place of the potassium in the soap, and uniting with the chlorine, goes into the lye, which readily separates from the soda soap. Fol lowing are good recipes for making hard and soft soap: After the raw soda or barilla is ground or pounded, it is placed in a vat in alternate layers with unslacked lime, the bottom layer being lime. Water is allowed to infiltrate through those lay ers, aud the lye is secured as it trickles through a hole in the, bottom of the vat. The lime absorbs the carbonic acid of the soda, making the lye caustic or fit for the soap-kettle; and the quantity- of lime applied must be in proportion to the quantity of carbonic acid in the soda,. To every twenty pounds of tallow add one gallon of weak lye, and boil until the lye is spent. The mass must then cool for one hour, the spent lye drawn off, and another gallon of strong lye added ; the mixture again boiled until the second dose of lye is spent ; and the same process must he repeated for several days, until the mixture. if properly managed, is converted into white tal low soap, which should be allowed to cool gradu ally and settle, when it is poured into molds, and when solid it is cut into the bars which are found in our markets. Twenty pounds of tallow ought to make thirty pounds of first-quality hard soap, allowing three pounds of soda-ash for every twenty pounds of tallow. The balance of the weight is made up by the large quantity of water which enters into cornhination with the grease and alkali in the course of saponification. When yellow or resin soap is required, the hard soap has to be made in the usual manner, and at the last charge of lye, or when the soapy ma-ss ceases to absorb any more lye, one-third the weight of pounded resin is introduced, the mix ture constantly stirred, and the boil kept up vigor ously until the resin has become incorporated with the_ soap. The whole must stand until it settles, and soap then dipped out. Resin soap, when well made, should be a fine, bright color. The principal difference between hard and soft soaps is, that three parts of fat afford, in general, fully five parts of hard soda-soaps; but three parts of fat or oil will afford six or seven parts of potash-soap of a moderate consistence. From its cheapness, strength, and superior solubility, potash-soap is preferred for many purposes, par ticularly for the scorning of woolens. The lyes prepared for making soft soaps should be made very strong. and of two densities, as the process of making potash or soft soap differs materially from that of making soda or hard soap. A por tion of the oil or fat being placed in the boiling pan and heated to near the boiling-point of water, a certain portion of the weaker lye is introduced and the fire kept up so as to bring the mixture to the boiling point; then some more oil and lye are introduced alternately, until the pan is filled. The boiling is continued gently, strong lye being added until the saponification is complete. The fire should then be removed, and some good soap, previously made, added while cooling down, to prevent any change by evaporation. One pound of oil requires about one-third of a pound of American potash, and will make one and three quarters to two pounds of well-boiled soap, con taining about forty per cent. of water. Sixty pounds of lard will make 100 pounds of first class soft soap by using one and a half cans of concen trated lye, made frcm salt, which is a soda lye.