1910.] PUBLIC DOCUMENT — No. 31. 137 



In the abseiioe of air, added moisture appeared to have no 

 effect as compared with the check on the unsaturated compounds, 

 while light both with and without moisture prevented oxi<lation 

 to some extent as measured by the iodine number (Table 2). 

 The experiments of Ritsert ^ proved that light, in the absolute 

 exclusion of air, could not produce rancidity, but the preserving 

 action here noted is a peculiar feature worthy of further study. 



Moist air increased the oxidation of the fat, with light and 

 added moisture contributing factors. Light in the presence of 

 moist air was destructive, a marked contrast to its action when 

 air was excluded. 



The hypothesis of Lewkowitsch,- supported by the investiga- 

 tions of Geitel ^ and Duclaux,'* offei*s an explanation of the 

 probable changes that take place in the development of rancidity 

 in oils and fats. The initial change he ascribes to the action 

 of moisture in the presence of fat-splitting enzymes. The free 

 fatty acids resulting from the hydrolysis are oxidized by the air 

 in the presence of light. Ritsert^ asserts that oxygen and light 

 must act simultaneously, neither of the agents alone being able 

 to produce rancidity. 



On the basis of the above assumption the hydrolysis of the 

 check samples must have been due to traces of moisture in the 

 fat and in the air between fat and stopper, and the oxidation to 

 the air and a very limited amount of diffused light. This may 

 be possible, as the changes were not, in themselves, excessive, 

 though rather out of proportion to the conditions prevailing. It 

 fails, however, to explain why similar samples in the light gave 

 less rather than equal or greater changes under conditions which 

 naturally should have been more favorable. The changes in the 

 open samples were not wholly in accord with the theory. Light 

 was a factor in oxidation, as was to be expected, but also in 

 hydrolysis, which is difficult to explain. With many points in- 

 decisive and others unconsidered, the prime object of the experi- 

 ment has been attained in showing that filtered butter-fat 

 samples of normal acidity can be satisfactorily preserved in well- 

 stoppered bottles. The action of high temperatures and sunlight 



' Untersuchungen iiber d. Ranzigwerden der Fette. Inaug. Dissert. Berlin, 1890. 



2 Chemical Technology and Analysis of Oils, Fats and Waxes, 3d Edition, Vol. I., pp. 23, 24. 



3 Journ. f. prakt. Chemie, 1897 (55), 448. 



* Annales de I'lnstitut Pasteur, 1887; Compt. rend. 102, 1077. 



