STERILIZATION OF OILS 63 



CHEMICAL CHANGES PRODUCED IN THE OIL BY EXPOSURE TO 

 ULTRA VIOLET RAYS 



The effect of the ultra violet rays on the oil itself was carefully 

 studied with the view of detecting the extent of the changes pro- 

 duced. The oils used were almond, cotton seed and olive. The 

 quantitative examination included the determination of the acid 

 value, the iodine value, Reichert-Meissl value, saponification 

 value, soluble acids, density, viscosity and refractive index. 

 These analytical values were obtained in each case with (a) the 

 raw oil, (b) oil that had been dried and filtered, and (c) dried and 

 filtered oil that had been exposed to ultra violet rays sufficiently 

 long to ensure sterilization. 



No significant change was noted in any of the above cases. 

 The two constants that would most likely be affected by ultra 

 violet rays are the iodine absorption number and the acid number. 

 If there were any tendency towards polymerization or resinifi- 

 cation, as is found to be the case with some unsaturated organic 

 compounds under the action of light, the iodine number would 

 be decreased. Oxidation would produce the same effect. If 

 the ultra violet rays affected the glycerol esters, causing them to 

 split into free fatty acids and glycerol, the acid value would be 

 markedly increased. As a matter of fact no significant change 

 in the oil could be detected by means of any of the constants 

 determined. In spite of these results, however, it is not reason- 

 able to say that ultra violet rays are wholly without action on 

 the oil. There is always a slight bleaching action and oil that 

 has suffered long exposure to ultra violet rays acquires a rancid 

 odor and taste. The bleaching action is probably due to the 

 action of the rays on carotin, the unsaturated hydrocarbon to 

 which certain oils owe their color (Gill, 1917). We can only 

 state that this action is without measurable effect when the oils 

 are exposed for the short periods of time necessary for their ster- 

 ilization. For all practical purposes the oil has all the properties 

 of the raw oil in the case of almond, cottonseed and olive oils 

 after this length of exposure. 



