CASTOK-OIL INDUSTRY. 35 



USES OF CASTOR OIL. 



Castor oil has properties which serve to differentiate it very mark- 

 edly from all other vegetable oils. This fact is no doubt attrib- 

 utable to the predominating influence of its characteristic acid 

 radical of ricinoleic acid. The striking properties of this acid are due 

 to the fact that it is a hydroxy acid, a condition which is only approxi- 

 mated in nature in the case of grape-seed oil. This hydroxylated 

 condition is probably the property which serves to render it so valu- 

 able in the industries, for it is apparent that when other oils are 

 treated so as to increase their acetyl number and their viscosity they 

 more nearly take on the properties of castor oil. Thus, when an oil 

 is oxidized (blown) it becomes less soluble in gasoline, audits viscosity 

 and acetyl value increase. In fact, the hydroxylation of acids 

 normally soluble in gasoline renders them insoluble in gasoline. 

 Sulphonated oils are insoluble in gasoline. Since hydrolyzing a 

 sulphonated oil is said to yield hydroxylated oils, efforts have ac- 

 cordingly been made in this and other laboratories to produce such an 

 oil, using peanut and cottonseed oils, but without success thus far. 



For ordinary lubrication, the viscosity of castor oil is its great asset. 

 Before the application of mineral oils for such purposes castor oil was 

 very largely used as a cylinder oil, but the production of high-grade 

 mineral cylinder oil has greatly displaced it except in the Tropics, 

 where it is still used for lubricating heavy machinery. However, in 

 gas engines, which are lubricated by spraying the lubricant into the 

 cylinder along with the gasoline (notably the rotary air-cooled types), 

 it has been found that castor oil is absolutely necessary. The prop- 

 erty of the solubility of mineral oils in gasoline is stated to be the 

 reason that they can not be so used as a lubricant, owing to the lower- 

 ing of their viscosity and "body" by solution in such a medium. 1 

 The insolubility of castor oil in such products is given as the cause 

 for its specific advantages in such cases. Some authorities assert 

 that castor oil is preferable to mineral oil because gasoline does not 

 wash it out of the crank case so readily, which is, of course, a corol- 

 lary of the above. However, mixtures of cylinder mineral oil and 

 castor oil treated so as to maintain their homogeneity are stated 

 after direct trial to be the more satisfactory, although such mixtures 

 are perfectly soluble in gasoline. Castor oil, of course, can be used 

 as a lubricant in other types of motors, but as the supply has been 



1 Although the literature almost universally states that castor oil is insoluble in gasoline, attention is 

 caOedtothefactthatthisqualitativestatementshould be restricted to refer only to conditions obtaining 

 at ordinary temperatures. A gentle heating effects ready solution; in fact, extraction of castor-press 

 cake pomace with gasoline is the industrial method for obtaining the lower grade oil, leaving a pomace 

 with about 2 per c3nt of oil. In view of the high temperature conditions obtaining in engines lubricated 

 with castor oil, itis apparent that this oilreadily dissolves in gasoline: consequently, its specific advan- 

 tage for lubrication under such conditions would not appear to reside in its insolubility in gasoline -but 

 rather to the fact that solutionin gasoline leavesit with a viscosity higher than that obtaining with other . 

 oils similarly treated. 



