The Home.

Digger (Invercargill RSA), Issue 16, 2 July 1920, Page 12

The Home.

TO CONVERT OIL INTO SOAP. 1. — If oily matters be mixed with water, they will rise to the surface; but if the water contains an alkali the oily matter will go into the Solution, forming an emulsion. When this solution yis boiled for some hours it becomes clear, being a solution of. soap. By adding common salt a curdling is produced. The curds rise to the surface, which, when collected and pressed from soap, glycerine remaining in the clear liquid. Scda is the alkali used in hard soaps, and potash in, soft soaps. 2.— A cheap soap may b,e made from 101b. of oil (linseed or rape, or mixtures), 17db. of caustic potash, and -41b. of caustic soda, Avith eig'nt or nine gallons of water. It is usual to commence the saponification with a lye of about 1.07 specific gravity, and finish with a lye of 1.15 specific gravity. By using soda in partial replaccment of potasa, much more water may be left in the finished soap, but this replacement is limited in amount, because too much soda causes a cloudiness, or hard white patches. .3, — The principal difference between hard and soft soaps is that three-parts of it afford, in general, fully five paris hard soda soap ; but three parts of 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, particnlaxly for the scouring of woollens. The lyes prepared for making soft soaps should be made very strcng, and of two densities, as the process of making potash or soft soap difiers

materially from that of making soda or hard soap. A portion of the oil being placed in , the boiling-pan, and heated to near the boiling pcint of water, • a certain portion of the weaker lye is introduced, . and the fire kept up so as to bring the mixture to the hoiling point; then soms more oil and lye are introduced gently, strong lye being added until saponification is complete. The pan should then be removed, and some good soap, previously made, added while cooling down, to prevent any change by evaporation. One pound of oil requixes about one-third of a pound of the best potash, and will make lflb. to 21b. of well-boiled soap, contalning about 40 per cent. of water. Sixty ponnds of lard will make 1001b of firstclass soft soap hy using one and a half cans of concentrated lye, which is made from salt> and is really soda lye.