Linseed-oil has a faint colour, and mild odour and flavour, when pure, but the commercial article is dark-yellow, with sharp repulsive flavour and odour. Its sp. gr. is at -18° (0° F.), a little solid fat separates out ; at -20° (-4' F.), it solidifies. By exposure to the air, after heating with oxide of lead, it rapidly dries up to a transparent varnish. The fresh oil saponifies readily, giving a yellow and very soft soap with soda ; by saponification, it yields 95 per cent. of fatty acids, chiefly linoleic, with a little oleic, pahnitie, and myristic acids. It dissolves in parts of ether, and in 32 parts of alcohol at 0.820 sp. gr. The oil is very extensively used in the manu facture of paint, printing-ink, floorcloth, artificial indiarubber, oil-varnishes, and soft-soap. For artists' use, it is purified by shaking up with whiting, and warming. Linseed-oil is never met with in commerce really pure, nor even the seed itself. Previous to the Crimean War, it was a recognized custom at the Black Sea ports to add 1 measure of hemp or other seed to every 39 of linseed. Since then, the proportion has advanced to 1 in 19, in addition to which, the Indian seed is grown mostly as a mixed crop with mustard and colza ; pure linseed-oil can only be obtained by picking out the seeds individually. The methods of refining this oil are described on p. 1460.
Mabo.-The seeds of a plant which is thought to be a Parinarium have been imported into England and Germany for the sake of their oil. They have intensely hard "stones," measuring about 21 in. by in., and are highly oleaginous, but it is a question whether the oil can be pro fitably extracted. They are brought from Liberia, and are closely allied to the mola plum of Zambesi land (P. Mobola), which is supposed to be identical with the noxa or nocha (?niko) of Lower Guinea.
Macassar-oil.-This oil was originally obtained from the unctuous fruit of Stadmannia [Cupania] sideroxylon, growing in the islands of Sunda and Timor, and usually known as kesambi wood. See also Safflower-oil, p. 1410, and llang-ilang-oil, p. 1422.
Madia-oil.-The seeds of Nadia sativa afford some 30-40 per cent. of fatty oil. The plant is a native of Chili, where it has long been cultivated for the sake of its oil. It has been successfully introduced into Asia Minor and Algeria ; its culture has also been attempted in S. France and in Wurtemburg, but without the success that was anticipated, mainly owing to the irregularity with which the seed ripens in these climates. It requires a sandy soil, and is very easily grown. In Europe, sowing takes place in October. The seeds must be threshed out soon after the stems are cut, or the latter ferment and cause injury. The seed resembles sunflower, but is much smaller.
The yield of oil from an acre of the plant is rather more than from colza (rape) : 1 hectare (21 acres) gives 726 kilo. (of 2.2 lb.) of seed ; and 100 kilo. of seed yield 32 of oil. It is extracted by expression, both cold and hot. It is deep-yellow, thick, and mild ; of sp. gr. 0.985 crude, and 0.9268 at 15° (59° F.) purified ; solidifies at -10° to -17° (14°-2° F.), according to the method of extraction ; dries slowly ; and dissolves in 30 parts of cold alcohol or 6 of boiling. The finer qualities may replace olive-oil ; the coarser are used for illuminating.
IYIahwa-oil.-The mahwa or mhowa (Bassia latifolia) is chiefly known as yielding flowers which are an important article of diet, and from which an intoxicating beverage is distilled, but it also claims notice as affording an oil. The tree is cultivated in most parts of India, and is abundant in Central India, notably in the Concans, the Circars, Bengal, Guzerat, and Rajputana. It is extremely hardy, thriving well on poor stony ground, and readily propagating itself by its seed. Its culture is therefore capable of the widest extension. The flowers are succeeded by fruits, whose kernels or seeds give some 33 per cent. of oil. The latter is obtained by bruising, rubbing, and pressing the seeds. It is greenish-yellow in colour, and of an oily consistence, when newly expressed, but immediately assumes a concrete state, remaining thus until a temperature of 43e F.) is reached. Its sp. gr. is 0.972 ; it is soluble in ether, scarcely in boiling alcohol. In a cool climate, the oil keeps good for a long time ; but in the plains of India, it acquires a bitter flavour and rancid odour after a few months' exposure to the air, separating into a heavy brown mass below, and a little clear fluid above. It saponifies easily, and the resulting soap is good as to quality and colour, and satisfactory as to quantity. The fatty acids are easily separable, by the simple process of " training " or "seeding," described on p. 1362. The proportion of stearic acid is about 40 per cent. ; it is inodorous while translucent, and is admirably adapted for candle making. The oleine separated is superior to that from tallow and palm-oil. For industrial purposes in this country, the oil has about the same value as coeo-nut-oil ; it has been imported into England and France from Calcutta for soap-making. Locally, it is extensively used by Bunniahs and Muhajuns for adulterating ghee; it is also employed in cooking and for burning. The residual cake forms food for man and cattle ; and the timber of the tree is valued (see Timber). Oils from other species of Bassia are Illipi-butter (p. 1392), Phulwara-oil (p. 1408), and Shea-butter (p. 1410).