Source, Etc

The oil expressed from the seeds of Linum usitatis-simum, Linne (N.O. Lineoe). (Compare ' Linseed,' p. 149).

Description

Yellowish-brown, with characteristic odour; specific gravity 0.930 to 0.940; iodine value not less than 170; unsaponifiable matter not more than 1 per cent.; does not congeal at temperatures higher than - 20°; exposed to the air in thin layers gradually hardens to a transparent varnish; consists of the glycerides of linolic, linolenic, isolinolenic, oleic, stearic, palmitic and myristic acids; may be identified by its odour, high iodine value, and by its hardening to a varnish; may be adulterated with mineral oil, rosin oil and fish oils; mineral oil may be detected by the rise in unsaponifiable matter; rosin oil by shaking with alcohol, evaporating the alcoholic solution, dissolving the residue in acetic anhydride and adding sulphuric acid, a red colour indicating rosin oil; fish oils are difficult to detect (compare Allen, 'Commercial Organic Analysis').

Linseed oil is used in pharmacy in liniments and as a laxative.

Note

Boiled oil is linseed oil which has been heated with litharge or other suitable 'driers' to about 150°; metallic salts of the fatty acids are formed and cause the oil to dry more rapidly.