This section is from the book "A Text Book Of Materia Medica, Being An Account Of The More Important Crude Drugs Of Vegetable And Animal Origin", by Henry G. Greenish. Also available from Amazon: A Text Book of Materia Medica : Being an Account of the More Important Crude Drugs of Vegetable and Animal Origin.
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.
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.