Tetramethylammonium hydroxide in methanol (TMAH) is used to catalyze the transesterification of the fat dissolved in diethyl ether; methyl esters form almost instantly. Glycerin drops out of solution to form a second layer containing the bulk of any free fatty acids present as the TMAH soaps. Gas chromatography of the ether layer gives the fatty acid composition of the glycerides. On injecting the lower layer, the TMAH soaps pyrolyze to form methyl esters. If methanol is added to the flask to solubilize the glycerin and excess base neutralized with methanolic hydrochloric acid, total fatty acid composition can be obtained by chromatographing the resulting solution. -- AATA