That which we import from the East Indies comes from Bombay and Calcutta, and is obtained at a very low price. It is exceedingly pure, both in color and taste.
In the West Indies the shrub grows about six feet high. The stalks are jointed, and the branches covered with leaves about eighteen inches in circumference, forming eight or ten sharp-pointed divisions, of a bluish green color, spreading out in different directions. The flowers contain yellow stamina; the seed is enclosed in a triangular husk, of a dark brown color, and covered with a light fur, of the same color as the husk. When the capsule is thoroughly ripened by the sun, it bursts, and expels the seeds, which are usually three in number.
In Jamaica this plant is of such speedy growth, that in one year it arrives at maturity, and I have known it to attain to the height of twenty feet. A gallon of the seed yields by expression about two pounds of oil.
The wholesale price in Liverpool, in October, 1853, was 3d. to 5d. per lb.
It is brought over from the East Indies in small tin cases, soldered together and packed in boxes, weighing about 2 cwt. each.
In Ceylon castor oil is obtained from two varieties of the plant, the white and the red.
The native mode of preparing the oil is by roasting the seed; this imparts an acridity to the oil, which is objectionable. By attending to the following directions, the oil may be prepared in the purest and best form. The modes of preparation are—1. By boiling in water. 2. By expression. 3. Extraction by alcohol. In the first the seeds are slightly roasted to coagulate the albumen, cleaned of the integuments, bruised in a mortar, and the paste boiled in pure water. The oil which rises on the surface is removed, and treated with an additional quantity of fresh water; 10,000 parts of clean seed give by this process (in Jamaica) 3,250 of oil, of good quality, though amber-colored. 2. Expression is the simplest and most usually adopted process; the cleaned kernels are well bruised, placed in cloth bags, and compressed in a powerful lever and screw press. A thick oil is obtained, which must be filtered through cloth and paper to separate the mucilage. In Bengal the manufacturers boil the oil water, which coagulates some albumen, and they subsequently filter through cloth, charcoal, and paper. 3. The extraction by alcohol is practised by some druggists. Each pound of paste is triturated with four pounds of alcohol, specific gravity 8.350, and the mixture subjected to pressure. The oil dissolved by the alcohol escapes very freely: one half is recovered by the distillation of the spirit, the residue of the distillation is boiled in a large quantity of water. The oil separates and is removed, and gently heated to expel any adherent moisture; then filtered at the temperature of 90 deg. Fahrenheit; 1,000 parts of the paste have by this process given 625 of colorless and exceedingly sweet oil.
The cultivation of the Palma christi, and the manufacture of castor oil, is extensively carried on in some parts of the United States, and continues on the increase. A single firm at St. Louis has worked up 18,500 bushels of beans in four months, producing 17,750 gallons of oil, and it is stated that 800 barrels have been sold, at 50 dollars per barrel. The oil may be prepared for burning, for machinery, soap, &c., and is also convertible into stearine. It is more soluble in alcohol than lard-oil.
American castor oil is imported for the most part from New York and New Orleans, but some comes from our own possessions in North America. In the United States, according to the "American Dispensatory," the cleansed seeds are gently heated in a shallow iron reservoir, to render the oil liquid for easy expression, and then compressed in a powerful screw press, by which a whitish oily liquid is obtained, which is boiled with water in clean iron boilers, and the impurities skimmed off as they rise to the surface. The water dissolves the mucilage and starch, and the heat coagulates the albumen, which forms a whitish layer between the oil and water. The clear oil is now removed, and boiled with a minute portion of water until aqueous vapors cease to arise: by this process an acrid volatile matter is got rid of. The oil is put into barrels, and in this way is sent into the market. American oil has the reputation of being adulterated with olive oil. Good seeds yield about 25 per cent. of oil. A large proportion of the drug consumed in the eastern section of the Union is derived by way of New Orleans from Illinois and the neighbouring States, where it is so abundant that it is sometimes used for burning in lamps.
In Jamaica the bruised seeds are boiled with water in an iron pot, and the liquid kept constantly stirred. The oil which separates swims on the top, mixed with a white froth, and is skimmed off. The skimmings are heated in a small iron pot, and strained through a cloth. When cold it is put in jars or bottles for use.