536. To Preserve Grease

536.    To Preserve Grease. Boil all the scraps, rinds, and bones, in a weak lye, and the purer grease in clear water. Let the mixture cool, take off the cake of grease, and strain it. It is well to do this occasionally, as you save it; for when kept a long time impure grease becomes offensive. You must be careful to dry off all the water before laying it away in the grease tub, if you wish it to keep sweet. The best plan to collect dripping is to put it while warm into water nearly cold. Any impurities it may contain will sink to the bottom.

537. To Bleach Palm Oil

537.    To Bleach Palm Oil. Dissolve 1/2 pound powdered red chromate of potassa in about a quart hot water. 100 pounds palm oil are heated in a wooden tank, by steam, to a temperature of 120° Fahr. The steam is then turned off and a portion of the chrome solution is stirred in, followed by a proportional quantity of 1 poundstrong muriatic acid. After the whole of the solution and of the acid has been thoroughly mixed with the palm oil, stir in 1/4 pound sulphuric acid. The oil becomes black, then dark green, and finally light green, with a thick froth on the surface. If, when the mixture has settled, the oil is not sufficiently bleached, the operation has to bo repeated, using less proportion of chrome and acids. "When the bleaching is complete, the oil is allowed to stand for an hour to clear; it is then run into a wooden tank with some water, and heated again, to wash out any salts that may remain in it, and after a time drawn off ready for use. Palm oil is usually combined with from 3 to 5 times its weight of tallow to make soap, and is serviceable in resin soap to brighten its color and disguise the resin.

538. Filled Soap

538.    Filled Soap. Hard soaps are usually made according to the process before described (see No. 520 (To Make Soap)), the excess of water being separated from the paste by the use of salt: this class of soap is termed grained soap. But there are some kinds - cocoanut oil and soda soap, for instance - that are so hard in their nature that the operation of salting, or graining, is needless, the water remaining incorporated in the paste; soaps of this class are called filled soaps.

539. To Make Tallow Soap

539.     To Make Tallow Soap. The French Method. Melt in a boiler, by a moderate heat, 500 pounds tallow; stir in, by degrees, 35 to 40 gallons caustic soda lye of 10° to 12° Baum'e, and let it boil gently for several hours; then add, gradually, 18 to 20 gallons caustic soda lye of 15° to 18° Baum'e, and mix until the whole becomes a homogeneous mass of a grayish color; keep the mixture boiling gently for some hours, adding to it every hour 3 to 4 gallons caustic soda lye of 20° Baum'e. This will occupy 10 or 12 hours. The salting process then follows, and is conducted as described in No. 520. After the separation or graining is finished the paste is allowed to stand for a few hours, and the lye is drawn off through a faucet inserted for the purpose in the side of the boiler, near the bottom. The mass is again boiled for some hours, adding every hour 21/2 gallons soda lye of 25° Baum'e, until the hard scales rise to the surface. (See No. 520 (To Make Soap).) The fire should then be extinguished, and after an hour the under-lye is to be drawn off. Then boil again for 11/2 to 2 hours with about 25 gallons soda lye of 4° Baum'e, stirring from time to time. The fire should then be removed, and the pan covered up; the soap will rise to the top of the lye, and may be poured into the frames, care being taken that no lye gets mixed with the soap. This should yield about 850 pounds of soap.