The tree is found growing abundantly in the Tinmeh country and near Sierra Leone, and occurs throughout Senegal and the Guinea Coast. The seeds (18-30 in one fruit) vary in size from a chestnut to a hen's egg. The oil is extracted from them by the natives of W. Africa in the following manner :--The seeds are sun-dried, and hung up in wicker racks or hurdles exposed to the smoke of the hut-fires. After sufficient exposure, they are roasted, and triturated in large wooden mortars till reduced to a pulp. The mass is then boiled, and the supernatant oil is skimmed off. It usually forms a concrete mass on cooling, resembling frozen olive-oil, but the best samples remain liquid at ordinary temperatures. It has a pale-yellow colour, and a strong bitter flavour ; the latter is due to an alkaloid principle, which is easily destroyed by boiling in water acidulated with sulphuric acid, allowing to settle, and then washing with fresh water to remove all traces of the acid. The oil is entirely soluble in ether ; alcohol separates it into (1) a concrete substance, which dissolves in the alcohol, and retains the odour and flavour, and (2) an oil fluid at ordinary temperatures, and nearly colourless and tasteless. By the Africans, the oil is used most largely for lighting purposes, but is also employed as a purgative and anthelmintic. Industrially, it is 4 u 2 capable of the same applications as crab-oil (p. 1386), and is imported into Marseilles from Senegal for soap-making. The seed is also shipped to France.
M'Poga.—The kernels of the nuts of the m'poga (probably a species of Parinarium), a tall tree abundant in the Gaboon, afford some 80 per cent, of unusually fluid oil, but difficult of extrac tion, on account of the hardness of the nut.
Mustard-oil (FR., Huile de Moutarde).—Three species of mustard are grown more especially for the well-known condiment which is prepared from the seeds ; these are Brassica [Sinapis] nigra, B. alba, and B. juncea ; for a description of their localities and modes of culture, the reader is referred to Spices—Mustard. The seeds of these species all yield fatty oils by expression. B. nigra affords about 23 per cent. (over 33 with ether) of a mild-flavoured, inodorous, non-drying oil, solidifying at —18° (0° F.), and consisting essentially of the glycerides of stearic, oleic, and erucic or brassie acids, the last-named being homologous with oleic acid. The fixed oil of B. alba amounts to 22 per cent. of the seed, and resembles generally that of B. nigra. The seeds of B. juncea, in Russia and India, afford by pressure 20 per cent. of oil, which is used like the best olive-oil, and for burning in lamps. These oils vary in sp. gr. from 0.9142 to 0.917, and are soluble in 4 parts of ether.
Other species of mustard, whose seeds are not prepared as a condiment, but which are utilized for their oleiferous properties, are as follows :—B. arvenis, the charlock, yields an excellent burning oil, and it is to be regretted that this common and troublesome weed, so abundant in Europe, has not been turned to better account. A mustard-plant thrives so well in California as to smother the corn in the fields. The seed is gathered by the Chinese and brought into San Francisco, where
the oil is expressed, and used as salad-oil. B. cernua is cultivated for its oil in Japan. B. chinensis is grown with the same object in immense quantities in China, notably in the Yangtze-kiang and Han-kiang river-valleys, in the provinces of Chekiang and Kiangsu, and to some extent also in the district of Ichang, province of Hoopih. It is in seed and ready for harvesting in the beginning of May. The seed is treated by a rude press, yielding a dark-yellow, pleasantly-odorous, thick oil, used for cooking, in lamps, and for anointing the hair.
An allied oil-plant is the colza or rape (see p. 1384).
and quantities of fatty oil are expressed from the seeds of two Indian species of Tenninalia, T. Bellerica, and T. Chebula, plants which are much more important on account of their astringent properties (see Tannin—Myrobalans). The oil of the first species readily separates into two portions, a pale-green,fluid, and a white, floccular semi solid. It is used locally for anointing and strengthening the hair. The oil of the second species is procurable only in very small proportion; it is a clear, transparent, almost colourless fluid, of medicinal use.
A third species of Terminalia, the jungle-almond of India (7'. Catappa), is much more widely distributed, and of greater importance as an oil-yielder. It is fouud abundantly in both E. and W. Indies, and grows freely in Mauritius and Bourbon. The fruits (nuts) are gathered, and exposed to the sun for a few days, to facilitate their breaking, which is one of the main items in the cost of extracting the oil. The kernels are next freed from shell, crushed, and cold-pressed. The oil is similar to almond-oil in flavour, odour, and sp. gr., but is deeper coloured, and deposits stearine by keeping. It is, however, very slow to become rancid ; and if carefully prepared and refined, it might well replace true almond-oil and hazel-nut-oil for most purposes.
Niger, Kersanee, or Oil.—The Niger seed" of African commerce, and the ram-til or kersanee of Indian cultivators, is the product of Guizotia oleifera. The plant grows wild on the Gold Coast of Africa, and is cultivated in Abyssinia, and in many parts of India, especially Mysore and the Deccan ; here the seed is sown in July-August, after the first heavy rains, the fields being simply ploughed, and neither weeded nor manured. The crop is cut 3 months after the sowing, and, after being sun-dried for a few days, the seed is threshed out, the produce being about 2 bush. an acre. By the common country mills, only 25 per cent. of oil is got from the seed, but better appliances bring the average up to 35. The oil is limpid, clear, pale, and sweet flavoured, and is used as an edible oil by the poorer classes of India, and commonly as a lamp-oil. Though much inferior to gingelly-oil, it is frequently used as a substitute for it, and to adulterate both this and castor-oil. The oil contains but little stearin or palmitic acid, hence soap made from it, though very white, is soft. The cake is an esteemed food for mulch cows.