STERILIZATION OF OILS 51 



probably some ferment or similar product contained in the cell 

 is modified by the rays and that thereby the cell is poisoned. 



With the innovation of lipovaccines, the question of an ade- 

 quate method of sterilizing the oil which serves as a vehicle for 

 the antigen has taken new form. Apparently it is difficult to 

 sterilize such oils as olive or cotton seed oil contaminated with 

 spore forming organisms without carrying the oil to a higher 

 temperature than is usually employed for sterilization. Again, 

 such oils heated for a time at high temperatures are found to be 

 irritating when injected subcutaneously (Le Morgine and Pinoy, 

 1916), probably due to the toxicity of the fatty acids and alde- 

 hydes split from the oil in the process of sterilization. Free 

 fatty acids (from butyric acid and upwards in molecular weight) , 

 in so far as they are soluble in water, and aldehydes, are poisonous. 



Because of the bactericidal properties of ultra violet rays, the 

 experiments detailed herein were made, with the view of testing 

 the applicability of rays of this type to the sterilization of cer- 

 tain oils. The oils employed in these experiments were (1) 

 sweet almond oil, (2) cottonseed oil of a grade known as Wesson 

 Oil, and (3) olive oil (Lucca Cream) . These oils as received were 

 usually very slightly opaque and contained a small amount of 

 water. As an emulsion of oil and water is opaque to ultra 

 violet rays, and as the presence of water in the oil is objection- 

 able in the preparation of lipovaccines since it causes autolysis 

 of the bacteria, the oils were dried and filtered. The principal 

 drying agents used were calcium chloride and anhydrous sodium 

 sulphate. Of these two the latter is quite satisfactory for 

 routine work. 



The dried oil after filtration was purposely inoculated with 

 various spore forming bacteria or molds and exposed to the ultra 

 violet rays. Portions of inoculated oil exposed in petri dishes at 

 various distances from the source of ultra violet radiation and 

 for various lengths of time established the fact that oil could 

 be completely sterilized by an exposure of 3-5 minutes at a 

 distance of 10 cm. The inoculated oil was chilled throughout 

 the exposure by floating the Petri dish on ice water. 



