STERILIZATION OF OILS 



53 



In another series of experiments, ten tests were made with 0.3 

 cc. of dried oil containing B. subtilis. The time of exposure was 

 two minutes in one case, four minutes in one case, five minutes 

 in one case and three minutes in the other seven cases. Agar 

 plates made after treatment were all sterile while control plates 

 were crowded. 



In these experiments the inoculated oil after exposure to the 

 ultra violet radiation was emulsified with beef infusion agar, 

 plated and incubated for periods up to forty hours. These re- 

 sults indicated that three minutes exposure at a distance of five 

 centimeters was sufficient to sterilize the oil effectively. Further 

 experiments were made with B. subtilis, in order to test the effect 



TABLE 2 

 B. subtilis in dried and filtered oil 



of the ultra violet rays upon the spores, since this is an important 

 test of the efficiency of the method of sterilizing oils. The re- 

 sults were as follows, exposure of the oil inoculated with B. 

 subtilis being always for three minutes; in eighteen tests made 

 with one emulsion (the voltage being 60 in six cases and 90 in 

 twelve cases) and in twelve tests made with a second emulsion 

 (the voltage being 60 in three cases and 90 in nine cases) all 

 plates were sterile after 16 to 40 hours. 



The results of another series of tests in which dried and 

 filtered oil was used are shown in table 2. 



The results obtained above in sterilizing oil that had been 

 inoculated with B. subtilis indicated that an exposure of the oil 

 for three minutes at a distance of five centimeters was sufficient 



