Source, Etc

The oil expressed from the seeds of various species of Gossypium (N.O. Malvaceoe).

The seeds are black, ovoid to rounded, 7 to 9 mm. long, 3 to 5 mm. wide; the section shows folded cotyledons with scattered, dark secretion cells.

They contain about 20 to 25 per cent. of fixed oil and about 20 per cent. of proteids. Crushed and pressed they yield about 13 per cent. of oil, the residual cake constituting a valuable cattle food. Cooled and pressed the oil yields a quantity of solid fat (chiefly palmitin), which is used in the manufacture of margarine, and a clear yellowish oil. They also contain a crystalline yellow substance of phenolic nature (gossypol) which passes into the (cold pressed) oil, but is extracted from it by alkalies which are always used in refining the oil.

Description, Etc

The crude oil expressed from the seeds is dark in colour, but after refining by a partial saponification it is pale yellow, odourless and of agreeable nutty taste. Specific gravity 0.918 to 0.925; begins to congeal at about 12°; iodine value 102 to 108; consists chiefly of the glycerides of oleic, palmitic, linolic and stearic acids. It may be identified by heating in a water-bath a mixture of 2 c.c. of the oil with 1 c.c. of amyl alcohol and 1 c.c. of a 1 per cent. solution of sulphur in carbon disulphide when a deep red colour is developed except in the case of oil which has been further purified by heating to 200°. Cotton-seed oil is largely used for making margarine and the lower qualities for soap.