A process used for the manufacture of soap. The process involves the hydrolysis of triglycerides using a strong base such as caustic soda to form a sodium salt of a carboxylate and glycerol. The triglycerides are esters of fatty acids obtained from vegetable (p. 337) and animal fats. The process of producing common soap involves blowing steam into large pans containing a fat such as glyceryl tristearate and a solution of sodium hydroxide to form sodium stearate and glycerol:

The soap is separated as a curd by adding strong brine. The lower aqueous layer is run off and processed to give glycerol. The soap is given further washes, left to reach the right condition for mixing with perfume and colouring before being run into frames for cooling. If the fat is hydrolyzed using potassium hydroxide, the resulting solution sets on cooling and yields a jelly known as soft soap containing water and glycerol.