Abstract
Trans-Octadec-16-enoic acid has been isolated from butterfat and characterized. The weight of trans-octadec-16-enoic acid isolated from the sample of summer butterfat investigated represented approximately 0.2% of the total weight of fatty acids. This acid has not formerly been isolated from a natural fat and characterized, although its presence in butterfat was deduced by Backderf (1956) and Backderf and Brown (1958), who conclusively identified thapsic acid as the main dicarboxylic component when appropriate C18 trans concentrates were oxidized with potassium permanganate and acetic acid.