A study of the tetrabromide method of estimating linoleic acid in fatty acid mixtures

Abstract

Summary When linoleic acid is brominated in cold petroleum ether, the yield of insoluble tetrabromides is empirical; it is affected by the composition of the petroleum ether and by the amounts of linoleic acid and of other fatty acids which may be in a given mixture. The tetrabromide number of pure linoleic acid ranges from 103.7 when a 2‐gram sample is brominated to practically zero with 10 mg. of the acid. Data are presented describing the tetrabromide yields of linoleic acid alone and in various mixtures with oleic acid, when brominated at the 2.0‐, 1.0‐, and 0.5‐g. levels of sample. From these data curves can be drawn by which it is possible to ascertain by interpolation the per cent of linoleic acid in a mixture. Seventeen concentrates of linoleic acid from corn oil, safflower oil, and butter fat have been assayed from the curves, and the results compared with values calculated from the iodine number. Several linoleic acid concentrates from corn oil were shown to contain appreciable amounts of isomeric dienoic acids. Examination of two linoleic acid concentrates from butter fat shows for the first time the indubitable presence of linoleic acid in this fat.