SOAP-MAKING

Waipa Post, Volume 32, Issue 1927, 28 October 1926, Page 7

SOAP-MAKING

SUBJECT OIF M-A-NY PROCESSES. Every civilised person lias at cne f.m-a or other, 'I hope, seen a- tablet oE soap; yojt how many have even the roughest idea of ’the many pr„cesses i has gone through '.before it i'.aches -.he hand's of the 'user? (writes Mr R. J. 'Sagar in Science Siftings). Soap, 1 y T -o way, is iby no means a recent iir, fan lion, far. a complete scap ■factory, estimated! alt about 1700 years old, was une-artheid in the excavations a;t Pompeii; ,bu)b dit was only about 500 years ago or less 'that people of England began to manufacture it, and it was in those times one of the highest forms of luxury, -taxed- to such an extent fell at only Ithe rich could afford Co buy it It may be said that soap is a combination of fats and alkali, but tills is not strictly tii-e -erase; many things are kaken out of this -composition and many put in before a serviceable soap is produced. ‘ The fa'ts most commonly are tallow and cocoanut oil,. These used are tallow and coc-oanut oil. Tli-ase are melted first, and; run into what is known a-s a boiling-pan, cr kcftlile, which ig merely a la-rgia; steel vessel with a capacity of anything up to 100 Itons, flitted with -steam -pipes for heajting purposes, and a cork near the bottom -for emptying. (Next, the- alkali is added', which is, lulsually in -the form of a sodium hydroxide solution, and -the whole contents mixed together and 'heated at ithe samfe itime by means of fairly high-,pressure s-team, and, in due course, -saponification sets in. “ Saponlification ” is the technical /tlerrn for ’fhe -chemical action of the alkali on the fats, which cause -the mass to become pasty-looking, due ito the formation lof -soap. Further supplies of fa-ts' and alkali are added, until the boiling-pan 1g about half full, and, when saponification has ceased, lllaa-v----ing a slight excess of alkali, common salt is -introduced', which causes the soap to be 'thrown out of solution, and to float as a granular, mass '-on Ithe top. The solution underneath contains a percentage of gly'dsrine, ■wlhlicli, not -many years ago, oilsed to be run Ito waste. 'However, -during the war glycerine was in great demand for use in th-e manufacture of explosives, and wals ,lihe-refore, recovered by evaporation and refined. Indeed, it may -be said tha't, whereas the glycerine used to be a by-product of soap, soap .became a -by-product of glycerine, so great wag. thje demand for it This -glycerine liquoT -having been run off from the pad, tile molten soap is treated with more alVkali to -ensure that no fats have escaped saponification, as this would cause -rancidity to develop. Water is added, and: the 'lot boiled for some time, and then allowed to settle over-night, when it will be -found thalt it has separated into thresa layers—-soap at the top. a weak solution of alkali at the bottom, and a very poor soft soap called “ nigre ” between .the two layk-rs. The -bottom two- layers are allowed to -run off, and the soap is transferred ! to (tanks for (storage if it is to be used for -toilet soap, or into wooden frames, wharfs it, is allowed to cool and be cut into bars for hou'sehold purposes'. -Shaving soaps are made in qu’ite a different way. The fats (usually stearine and cocoanut oil) are first mtelted in the ,pan with alkali until saponification commences, and -then -th}a steam is turned off. The chemical action is so vigorous that enough heat is generated by it to complete combination of Ithe- fait and the alkali.