522. Common Yellow Soap

522.    Common Yellow Soap. Common yellow hard soap consists of soda, with oil or fat and resin. Resin is a feeble acid, capable of combining with alkali, but neutralizing it less completely than oil, so that the compound or soap formed is too powerfully alkaline. But when resin is worked with an equal or larger proportion of oil, it makes an excellent soap for many purposes.

523. Beef Tallow

523.    Beef Tallow. This fat, on account of its abundant supply, is the most used by soap and candle makers. It is not as white as many other animal fats, and the best quality, the North American, contains about 70 per cent, of stearine. It does not melt below 111° Fahr., but may afterwards be cooled down to 102° without solidifying, and when cold, is firm, and even brittle.

524. Mutton Suet

524.    Mutton Suet. This is generally firm, white, and very rich in stearine; this latter quality gives it a tendency to produce a soap of too hard and brittle a nature for general use, which is obviated by mixing about one-fifth or one-sixth part of lard, or some other more oleaginous fat; thus modified it is specially adapted for stock for toilet soaps.

525. Lard

525.    Lard. The best quality of lard melts at 81° Fahr., and contains about 60 per cent, of oily fat, known as lard oil, and about 30 per cent, solid stearine. It makes a pure, white soap, and is frequently combined with tallow or other saponaceous fat.

526. Bone Fat

526.    Bone Fat, obtained by boiling fresh bones, split open lengthways, is very well adapted for making soaps, but generally undergoes a process of purification before being thus employed. (See No. 534 (To Purify Bone Fat).)

527. Cocoanut Oil

527.    Cocoanut Oil possesses two prominent qualities which specially recommend it as an ingredient in soap-making. It imparts a great degree of firmness to the soap, probably owing to the solid form of the fatty acids found in it. It will also unite permanently with soda lyes in any proportion; and, in combination with other fat substances, imparts whiteness and emollient properties to them; it also froths as well in cold as in hot water, which is not the case with tallow soaps worked with soda.

528. Palm

528.    Palm. Oil. This substance is used in the manufacture of soap. Its genuine quality is easily tested by its solubility in acetic ether, the imitations sometimes sold under the same name being insoluble in it. It is used in its natural state, but its distinctive qualities and white color are greatly increased by bleaching. (See No. 537 (To Bleach Palm Oil).)

529. To Clarify Fat Used in Making Fine or Toilet Soaps

529.    To Clarify Fat Used in Making Fine or Toilet Soaps. Heat the fat in a clean iron or copper kettle, applying just heat enough to melt it thoroughly; then filter it through fine linen or muslin.