76 PLANT COMPOUNDS 



oxidation process, resulting in the formation of a hard, resin- 

 ous compound, and not a desiccation which is the case in 

 true drying. Non-drying oils may be used as lubricants, 

 but drying oils are not suited for this purpose, since the 

 "drying" would make them lose their lubricating qualities. 



69. Some Common Fixed Oils. — (a) Castor Oil is a thick, 

 viscous, transparent, colorless or slightly yellow oil of dis- 

 agreeable taste. It is pressed from the seeds of the castor 

 bean which contain about 50 per cent, of oil, and is composed 

 of small amounts of stearin but principally of ricinolein, the 

 latter being the glyceride of ricinoleic acid, a hydroxy-acid 

 with one double bond, G/H32OH.COOH. It is used in 

 medicine; for making soap; and as a lubricant for heavy 

 machinerv, since it is verv viscous and does not "drv" 

 appreciably. 



(b) Corn Oil is a pale yellow, fluid oil, with a smell of 

 corn meal. It is composed mostly of olein and linolein 

 and is a semi-drying oil. It is derived by pressing the germs 

 which have been removed from corn kernels previous to 

 the manufacture of starch (Fig. 5). It is used largely in 

 making soap, oil-cloth, and as an adulterant of edible oils. 

 The press cake is an excellent cattle food. 



(c) Cottonseed Oil, when purified, is a straw colored, 

 pleasant tasting oil, composed of palmitin, stearin, olein, 

 and linolein. It is made from husked or decorticated cotton 

 seeds by pressure when hot, and the resulting oil, IS per cent, 

 yield, is clarified. By cooling below 12° C. the solid fats, 

 palmitin and stearin, separate out and can be obtained by 

 pressing. "Cottonseed stearin" is used in making butter 

 substitutes, such as oleomargarine. The original oil is used 

 as a substitute for olive oil and to adulterate olive oil, 

 but principally in soap making. The press cake is used for 

 cattle food. 



(d) Linseed Oil is obtained by cold pressing or hot press- 

 ing the seeds of the flax plant (Fig. 26 shows a field of flax 

 in blossom). The seeds contain from 30 to 40 per cent, of 

 oil. The cold pressed product is clear and yellow, containing 

 less solid glycerides and hence is a better drying oil. It 

 is also used as a food in some countries, whereas the hot 



