Chemical Composition of Linseed Oil

The chemical composition of linseed oil may now engage our attention. Its ultimate analysis shows it to vary according to the method of extraction adopted, cold-pressed oil containing about 78 percent of carbon, 11 percent of hydrogen, and 11 percent of oxygen; while the hot-pressed oil contains nearly 3 percent less carbon, and nearly 3 percent more oxygen - linseed oil, extracted by carbon disulphide, is still poorer in carbon, and richer in oxygen. It appears that linseed oil consists chiefly of three glycerides, called, respectively, linolein, linolenin, and olein. A small, but variable, amount of free fatty acids, such as palmitic and arachidic, is also present. The empirical formulæ of the three fatty acids of the above-named glycerides are, respectively:

Structure of linolein - a triglyceride.

Linolein, which is present in linseed oil to the extent of about 20 per cent., is the glyceride of linoleic acid, and has the formula C₅₇H₉₈O₆. The relation of this glyceride to glycerin may be seen when the latter body is expressed by the formula, C₃H₅(OH)₃. It is probable that the other main constituent of the oil - linolenin - is a similarly constituted glyceride, and that it closely resembles linolein in physical and chemical properties. When 100 parts of linseed oil are saponified by an alkali, they yield from 9.4 to 10 parts of glycerin.