322 



GERMICIDAL ACTIVITY OP EUCALYPTUS OILS, 11., 



aromadendral and piperitone are like cineol in this respect, but 

 the Eucalyptus oils generally are different, their curves usually 

 showing a more sustained rise. While theoretically the real 

 coefficient should be the highest, practically we want to know 

 the maximum efficiency in the shortest time so that there might 

 be a minimum of risk in the disinfection of infectious material. 

 The half-hour interval is clearly indicated for cineol and, as we 

 shall see later, for aromadendral and piperitone, as well as for 

 the pinene and sesquiterpene oils. 



The question of the choice of cineol as a disinfectant will 

 depend upon circumstances. While phenol forms clear solutions 

 with water in dilutions of 1 : 20 and weaker, cineol, according to 

 the data of Earle,* would at 20" give a clear solution with 1 :270. 

 The strongest clear solution of cineol destroys B. coli communis 

 in 15 minutes at 20°, while the strongest clear solution of phenol 

 kills it instantly. On the other hand, a 1 : 270 dilution of 

 phenol would not destroy the bacillus within a reasonable time. 

 In dilutions stronger than 1 : 270, cineol forms milky emulsions 

 which throw oil globules to the surface upon standing for a few 

 minutes, and on this account it does not give what is termed an 

 elegant preparation. 



The oil of E. cinerea. — The crude oil of E. cinerea usually con- 

 tains over 50% of cineol, the remainder being pinene, with a 

 comparatively large amount of esters and some sesquiterpene. 

 The first specimen to be examined was that which gave the high 

 toxicity numbers when tested in oil. It had an acidity of 95°, 

 and, judging by this, some time, probably some years, had passed 

 since its preparation. Two and a half months after the first 

 set of tests, the oil was treated with dry sodium carbonate for 

 two days and dilutions were made by two methods, the mass and 

 the droplet. The idea was to test the two methods, and at the 

 same time to slightly vary the conditions of the experiment. So 

 far as the method is concerned, it appears to be immaterial 

 which is used, as a, b, c, and e were made by the droplet and d 

 by preparing a bulk dilution of 1 : 200 and making the other 

 dilutions from that. 



* Journ. Soc. Chem. Incl., 1918, 274T. 



