Commercial process for splitting fats to glycerol and fatty acids by heating the sulfuric acid–washed fat 20–48 hours in an open tank with steam in a mixture of 25–50% water, 0.5% sulfuric acid, and 0.75–1.25% Twitchell reagent. The original Twitchell catalyst was prepared by sulfonation of a mixture of fatty acid and benzene, but toway sulfonated petroleum products are used.