CASTOJi OIL SEED. 



407 



capsules, are submitted to a gentle heat, not greater than can be borne 

 by the hand, which is intended to render the oil more fluid, and 

 therefore more easily expressed. The whitish oily liquid thus ob- 

 tained is boiled with a large quantity of water, and the impurities 

 skimmed off as they rise to the surface. The water dissolves the 

 mucilage and starch, and the albumen is coagulated by the heat, 

 forming a layer between the oil and water. The clear oil is now 

 removed, and boiled with a very small quantity of water, until 

 aqueous vapour ceases to rise, and a small portion of the oil taken out 

 in a phial remains perfectly transparent when cold. The effect of 

 this operation is to clarify the oil, and to get rid. of the volatile acid 

 matter. Great care is necessary not to'carry the heat too far, as the 

 oil would thus acquire a brownish colour and acid taste. 



In the West Indies the oil is obtained by decoction, but none of it 

 appears in commerce in this country. 



In Calcutta it is thus prepared : The fruit is shelled by women ; 

 the seeds are crushed between rollers, then placed in hempen cloths, 

 and pressed in the ordinary screw or hydraulic press. The oil thus 

 obtained is afterwards heated with water in a tin boiler until the 

 water boils, by which means the mucilage and albumen are separated. 

 The oil is then strained through flannel and put into canisters. 



Two principal kinds of castor seeds are known, the large and the 

 small ; the latter yields the most oil. The best East Indian castor 

 oil is sold in London as "cold drawn." In some parts of Europe 

 castor oil has been extracted from the seeds by alcohol, but the 

 process is more expensive, and yields an inferior article. 



Castor oil is a viscid oil, generally of a pale yellow colour, a 

 nauseous smell and taste. Its specific gravity, according to Saussure, 

 is 0*969 at 53° Fah. The acid taste which it sometimes possesses 

 may be removed by magnesia (Gerhardt). At about 6° Fah. it 

 forms a yellow, solid, transparent mass. By exposure to the air, it 

 becomes rancid, thick, and at last dries up, forming a transparent 

 varnish. It dissolves easily in its own volume of absolute alcohol ; 

 castor oil and alcohol exercise a mutual solvent power on each other. 

 It is also soluble in ether. 



There are chiefly three sorts of castor oil found in the London 

 market ; viz. the oil expressed in London from imported seeds, East 

 Indian oil, and the American or United States castor oil. Castor oil 

 is imported in tins, barrels, hogsheads, and duppers. It is purified 

 by decantation and filtration, and bleached by exposure to sunlight. 



It is not quite decided how many kinds of fats castor oil contains ; 

 according to Gerhardt several, but Saalmuller says only two. It is, 

 however, principally composed of ricinoleine, with perhaps a little 

 stearine and palmatine, and an acid resin. Its ultimate composition 

 is shown by the following comparative analyses : 



Carbon 

 Hydrogen 

 Oxygen . 



74-00 

 10-29 

 15-71 



74-18 

 11-03 

 14-79 



74-35 

 11-35 

 14-30 



Total 



100-00 



100-00 



100-00 



