Flaxseed Oil

FLAXSEED OIL, Oleum Lini (Ph VII), is obtained by pressing flax seeds, Linum usitatissimum L. (family Linaceae). Since the 4th century, flax oil has been used for making oil paints, and since the 10th century, it has been used to prepare oil varnish (with lead white). Flax (see figure) is cultivated in all countries. In the USSR, flax is grown on a large scale in the central part of the European portion. The oil content in the seeds of our flax is about 30%; flax seeds of Indian origin contain up to 40% oil. Generally, the further south the flax is cultivated, the more oil is contained in the seed. Flax oil is a typical representative of the so-called 'drying oils'; it is rich in glycerides of fatty acids of high degree of unsaturation (especially linolenic acid) and is characterized accordingly by high and rapid oxidizability and rancidity, as well as the ability to polymerize. Painted in a thin layer, it thickens and hardens due to the easy oxidizability of oxygen in the air; at the same time, an elastic, non-greasy film is formed, which is why such oils are (unfortunately) called 'drying oils'. Constants — see Fats. Medical flaxseed oil must not exhibit a rancid smell or taste. Admixtures to flax oil. The presence of mineral oil is detected by determining non-saponifiable substances; cottonseed oil is detected by the Galfen reaction (see Fats); other fatty oils are usually more expensive than flax oil and therefore are not added unless they are spoiled; the presence of such oils can be judged by the iodine number and other constants (see Fats). In medicine, flax oil is used in the preparation of liquid lime ointment Linimentum calcis (Ph VII), used for burns, and of 01. Lini sulfuratum, which is part of the Haarlem balsam (01. Lini sulfurato-terebinthinatum, Ph IV). Flax oil obtained by cold pressing has extremely important significance for us as a food fat. Flax oil is indispensable in the preparation of oil varnish, oil paints, varnishes, linoleum, rubber substitutes (factis), and so on.