It grows mainly in Central and Western China, North Vietnam. Cultivated in China and other states of Tropical Asia, Africa, South America, West Indies, Australia, New Zealand, subtropics of the USSR.
Deciduous tree 8-10 m tall. Leaves are alternate, glabrous, leathery, 7-20 cm long, broadly ovate or heart-shaped, long-petiolate. Inflorescences loose, from heterosexual flowers. The fruits are drupe-shaped, large, up to 6 cm in diameter, smooth, on long stalks, mature – woody, dark brown. The seeds are large, the seed kernel is ivory, oily.
Seeds contain 48-57% fatty oil, unsurpassed in quality, which dries quickly. It is approximately 80% composed of eleostearic acid:
The peculiar chemical configuration of this acid gives tung oil its specific properties – the ability to polymerize and dry quickly. A film of tung oil protects metal from corrosion, and wood from soaking, destruction by fungi, etc. The technical significance of tung oil is enormous. It is valuable for medical equipment, for applying an anti-corrosion film. In medicine in China and the countries of Indochina, it is used as an emetic and laxative, and is also part of ointments for boils and burns.
The plant contains liquid fats (oils).
PLANTS CONTAINING FATS (FATTY OILS)
Fats are composed almost entirely of triglycerides of high molecular weight fatty acids. They are accompanied by pigments, sterols, vitamins and some other fat-soluble substances.
The fatty acids that make up triglycerides can be saturated or unsaturated. Most often, triglycerides contain the fatty acids listed in the table.
Fats are not individual substances – they are mixtures of triglycerides. In the formation of fats, the law of maximum heterogeneity prevails – more than 1300 currently known fats are formed by “multi-acid” triglycerides, and fatty acids of different composition (for example, stearinodiolein, palmitinooleinolinolein, etc.). Fats, consisting of “single acid” triglycerides, are relatively rare in nature (olive oil is triolein, castor oil is triricinolein).
The properties of fats are determined mainly by the composition of fatty acids and their quantitative ratio. Saturated fatty acids form triglycerides of a dense consistency (at traditional temperature), and the density increases with an increase in the number of carbon atoms in the acid (see table). Unsaturated fatty acids form liquid triglycerides.
Liquid fats (oils), spread with a thin layer, can remain liquid (non-drying fatty oils) or, oxidized, gradually turn into a resinous film (drying – a dense film and semi-drying – a soft film). Fatty oils dominated by oleic acid triglycerides are non-drying. The more linoleic and linolenic acids in the oils, the more they are prone to drying out, as can be judged by the iodine number (the number of grams of iodine that can join 100 g of fat at the place of double bonds of unsaturated acids). Approximate limits of iodine numbers: non-drying 80-100, semi-drying 100-140, drying oils 140-200.
Most vegetable fatty oils are obtained by pressing or extracting raw materials with volatile solvents. Freshly obtained (“raw”) fats are purified (refined).