84 



GERMICIDAL ACTIVITY Of EUCALYPTUS OILS,!.. 



them more toxic. A preliminary experiment with acetic, pro* 

 pionic, isobutyric, and valeric acids, gave a certain amount of 

 promise that the addition of acetic acid would increase the bac- 

 tericidal properties of the oils, and a further test was made. In 

 this, acetic acid* did, in some cases, increase the toxicity, but the 

 higher acids were without effect upon the rectified oil of E. 

 polybractea. The results are shown in the following Table. 



Table iv. — .'/. aureus. 



Oil and date of acidi- 

 fication. 



Bactericidal percentage dilution, 

 2 hours at 20°. 



5 



Oineol 11/7 ... ... 000 



Essential oil 11/7 ... 95 



E. dives, crude 26/7 ... 50 

 E. cinerea, crude 29/7 000 

 K polybractea, reel. 29/7 000 

 E. polybractea, rect. 12/8 01 M.I 

 E. dives, crude 12/8 ... 50 



16/7 



26/7 



29/7 



(Mill 

 90 



5/8 12/8 22 8 



50 4(1 

 30 



000 — 



70 60 



— (MMI 



— 40 



100 

 60 



000 

 4(1 



4/9 



oil 



(MM) 



50 



000 



Mi 



IllMI^ inactive. 



An increase in the bactericidal power, as indicated by the 

 reduction in the lethal percentage of oil, was obtained with the 

 crude Essential Oil purchased from the druggist, with E. dives, 

 crude, and in one test with E. pul ybractea, rect. E. cinerea, 



'"' This is the most pronounced acid in the Eucalyptus oils. It is derived 

 largely from the acetic acid esters they contain, and also from the oxida- 

 tion of the corresponding aldehyde. Practically all Eucalyptus oils con- 

 tain low boiling aldehydes which arc more pronounced in the oils of some 

 species than in others Butaldehyde and valeraldehyde are quite com- 

 mon, and in many oils of one class, the ester, butylbutyrate, is a common 

 constituent. The oxidation of the aldehydes to acids and the alteration 

 of the esters are responsible for the presence of the acids in the oils, and, 

 naturally, the older the oils the more acid they become 



