The fresh seeds when shelled afford a large quantity of oil, amounting even to 60 per cent. by weight. In India, this is extracted in the following manner. The mature seeds are gathered, and beaten with a small wooden hammer or similar instrument, to separate the shell from the kernel ; the latter is then cut into slices, sun-dried, and triturated in the common country mill. The result is a yield of about 33 per cent. of a dirty, dark-green, disagreeably odorous oil, the thick ness and depth of colour augmenting with the age of the seed. No method of refining ie attempted. The cake is used as fuel, and sometimes for illuminating, but is not consumed as cattle-food, nor applied as a manure. It is said that, in the Calcutta market, this oil cannot compete with castor oil for industrial purposes in its present crude condition, though in Burma it fetches about 4 times the Calcutta price of castor-oil. Doubtless it might be very much improved by extracting it by means of simple hydraulic pressure, instead of subjecting it to the friction of the mill. In the Society Islands, the kernels are exposed to the sun for about two months, reduced to powder, and pressed in linen sacks. When the oil ceases to run, the cakes are broken up, exposed to a gentle heat to coagulate the albumen, and again put under the press. Thus a second flow of oil is induced. The first exudation would be much facilitated by warming the powder, but the product then becomes much more quickly rancid. The usual results of the operation are stated thus : 100 lb. of entire nuts give 39 lb. of kernels ; 100 lb. of kernels give 41 lb. of oil by the first expression, and an additional 40 lb. by the second, or a total of 81 per cent. In Fiji, the mature fruits are allowed to fall to the ground, and lie until the fleshy covering has rotted. The remain ing kernels in their shells are baked on hot stones ; the shells are then broken, and the kernels are ground to powder. The macerated mass is then placed in an exceedingly rough kind of filter press, made of the fibre of one or more species of Hibiscus (see Fibrous Substances, pp. 961-2), and thus a portion of the oil is extracted. The pressure is quite inefficient, and much of the oil is thereby wasted. It will be noticed that preliminary heating of some sort is common to all the processes, probably indicating that the oil does not exist ready formed in the kernels, but is deve loped by heat.
The oil varies in colour from greenish-yellow to deep-green, possesses a peculiar disagreeable flavour, and an odour which is described as fragrant by some but unpleasant by others. These qualities are all ascribed to the resin wINch it holds in solution. The oil may be separated from this resin by treatment with alcohol, the resin being dissolved by this agent, while the oil remains insoluble. The latter is also insoluble in ether and chloroform. Treating with 2 per cent. of sul phuric acid, and subsequently washing with hot water, is perhaps a simpler and cheaper method of purifying the oil. The sp. gr. of the oil is Its congealing-point and boiling-point are not known ; it is liquid at ordinary temperatures, begins to thicken when cooled below 10° (50° F.), but is said not to be solid at —4° (25° F.). Locally, the oil has a great reputation as a remedial agent in rheumatism and similar affections ; it is also employed for ointments, and largely as an illumin ator, but not for culinary purposes. As regards its future utility, experiments show that, when freed from the resin, it makes an excellent, coloured, aromatic soap ; it mixes readily with pigments, and, applied as paint, whether previously boiled or not, dries completely within 12 hours. For merly there was a considerable export of the oil from Madras, the shipments in 1847-8 having been 3871 gal. of the oil and 508 cwt. of the seed, to Ceylon and the Straits.
The tree further affords a resin (see Resinous Substances—Tamanu).
The seeds of the Indian species C. Walkeri [decipiens] of S. India and Ceylon, and C. Wightianum [spurium, decipiens] of the mountains on the W. coast of the W. Peninsula, yield oils differing but little from that obtained from C. inophyllum, and are probably the sources of the oil erroneously referred to C. Calaba, which is not an E. Indian tree. Other species afford Calaba- and Keenatel oils (see pp. 1379, 1392), the former in the W. Indies, the latter in Ceylon.
Dogwood-oil.—The berries of the dogwood (Cornus sanguinea), in Italy, Siberia, and Cashmere, are utilised for their oil. It is extracted by crushing the entire berries, boiling them, and skimming off the oil as it rises : the albumen is then removed by boiling the crude oil in water strongly acidulated with sulphuric acid. Properly prepared, it is edible, and said to be so applied in Italy more usually it is applied as a lamp-oil ; it also makes good soap. In Germany, an illuminating oil is obtained from another so-called " dog wood-" or skewerwood-tree (Euonymus europceus).
Gamboge-butter.—The seeds of the Garcinia pictoria (see Pigments—Gamboge), a good-sized tree, common in the forests of Coorg and W. India generally up to 3500 ft., afford a yellow-coloured semi-solid fat, which is used by the better natives as a lamp-oil, and by the poorer as a substitute for ghee. It is extracted by pounding the seed in a mortar, and boiling the paste until the oil rises to the surface.
Gingelly-, Sesame-, Til-, or Benn4-oil (Fa., Huile de Sesame ; GER., Sesamol).—Gingelly oil, whose name is variously spelt, is obtained from the :seeds of Sesatnum indicum [orientale], an annual plant 2-4 ft. high, indigenous to India, but long since propagated by cultivation in almost all tropical and sub-tropical countries, and now found nowhere in the wild state. There appears to be only one true species, but Indian cultivators distinguish two varieties—a white-seeded, called suffed-til; and a black-seeded, called kala-til. The two kinds are by them never sown together, but each is grown as a mixed crop with other plants. The white-seeded, commonly called " second sort," is sown in June, and ripens in August ; the black-seeded, or " first sort," which is much the more common, is sown in March, and ripens in May. The mode of cultivation usually adopted is sufficiently simple. Ploughing is commenced towards the end of February, and is com pleted before the middle of March. If no rain has fallen some time previously, the field is irrigated ; it is then ploughed three times, the seed being sown broadcast immediately before the 3rd ploughing, by which it is covered. Sometimes manuring and weeding receive attention, and occasionally a second irrigation is given. The soil preferred is red loam, but sand is also suitable. The crop is generally considered exhausting. It is commonly reckoned that an acre requires A bush. of seed, and yields 11-2 bush., occupying the land for about 3-4 months. When ripe, it is cut down, and stacked for 7 days ; it is then sun-dried for 3 days, being collected into a heap at night, and kept in heap on alternate days between the sun-drying. This causes the bursting of the pods and the liberation of the seed. The latter is subjected to frequent washings in cold water, and subsequent exposure to the sun, with the object of bleaching it, and the oil is extracted by pressure. In India, the common yield is 2 qt. of oil from 9 lb. of seed ; it may be said to range between 45 and 50 per cent. by the,00mmercial processes in vogue, though it is present to the extent of 56 per cent. and upwards.