Anionic surfactants are manufactured and used in greater volume than all other types of surfactants. Soap, the alkali metal salt of a carboxylic acid, derived from natural oils and fats, has been used as a detergent for thousands of years. Soap is defined as the product formed when glycerides or fatty acids are heated with alkalis or organic amines. Personal (toilet) soaps are made by reacting animal fats and/or vegetable oils with caustic soda solutions. Fatty alcohols are produced from methyl esters of fatty acids by catalytic high pressure hydrogenation. In principle, hydrogenation could start with the triglycerides, but the harsh conditions result in poor glycerine recovery and greater use of hydrogen and catalyst. The sarcosinates, taurates, and isethionates are produced from fatty acids by first making the acid chloride and then reacting this with the appropriate active group.