ABSTRACT
Introduction Glycerol [Chemical Abstracts Registry #56-81-5; also propane-1,2,3-triol, glycerin (USP); see Fig. 1 in Chapter 1], a trihydric alcohol, is a clear, water-white, viscous, sweet-tasting hygroscopic liquid at ordinary room temperature above its melting point. Glycerol was first discovered in 1779 by Scheele, who heated a mixture of litharge and olive oil and extracted it with water. Glycerol occurs naturally in combined form as glycerides in all animal and vegetable fats and oils, and is recovered as a by-product when these oils are saponified in the process of manufacturing soap, when the oils or fats are split in the production of fatty acids, or when the oils or fats are esterified with methanol (or another alcohol) in the production of methyl (alkyl) esters. Since 1949, it has also been produced commercially by synthesis from propylene [115-07-1]. The latter currently accounts for ~25% of the U.S. production capacity and ~12.5% of capacity on a global basis.
