Soap-Making Manual; a practical handbook on the raw materials, their manipulation, analysis and control in the modern soap plant

Excerpt: ...of saponification consists of causing an almost complete cleavage of fats and oils by the use of the Twitchell reagent or saponifier, a sulfo-aromatic compound. This is made by the action of concentrated sulfuric acid upon a solution of oleic acid or stearic acid in an aromatic hydrocarbon. From 0.5 per cent. to 3 per cent. of the reagent is added and saponification takes place from 12-48 hours by heating in a current of live steam. The reaction is usually accelerated by the presence of a few per cent. of free fatty acids as a starter. Recently the Twitchell double reagent has been introduced through which it is claimed that better colored fatty acids are obtained and the glycerine is free from ash. The advantages claimed for the Twitchell process as outlined by Joslin 12 are as follows: 1. All the glycerine is separated from the stock before entering the kettle, preventing loss of glycerine in the soap and removing glycerine from spent lye. 2. The liquors contain 15-20 per cent. glycerine whereas spent lyes contain but 3-5 per cent. necessitating less evaporation and consequently being more economical in steam, labor and time. 3. No salt is obtained in the liquors which makes the evaporation cheaper and removes the cause of corrosion of Pg 114 the evaporator; also saves the glycerine retained by the salt. 4. The glycerine liquors are purer and thus the treatment of the lyes is cheaper and simpler and the evaporation less difficult. 5. The glycerine can readily be evaporated to 90 per cent. crude rather than 80 per cent. crude, thus saving drums, labor in handling and freight. The glycerine furthermore receives a higher rating and price, being known as saponification crude which develops no glycols in refining it. 6. The fatty acids obtained by the Twitchell saponifier may be converted into soap by carbonates, thus saving cost in alkali. 7. There is a decrease in the odor of many strong smelling stocks. 8. The glycerine may be obtained from half...