78 GERMICIDAL ACTIVITY OF EUCALYPTUS OILS,!., 



Group iv. — The oils never contain more than 30% of cineol, 

 the other constituents being pinene and aromadendral. 



Group vi«. — The oils never contain more than 30) of cineol. 

 The chief constituent is pliellandrene, and there is some pipcri- 

 tone. 



Group vi^/. — Cineol is almost absent. The chief constituents 

 are pliellandrene and piperitone. 



Some of the oils were, at first, tested several times to determine 

 the accuracy of the method, and it was found to be quite trust- 

 worth}' when the dilutions were made in steps of 10, i.e., falling 

 by 10% progressively from the undiluted oil through 90%, 

 80%, and so on to a 10% dilution. 



Several samples of the same kind of oil gave the same toxicity- 

 numbers, and it was afterwards learned that they had been taken 

 from one original specimen. The rectified oil of E. cinerea is a 

 case in point; the identity of the toxicity and the acidity-numbers 

 brings this out clearly. 



The oils of E. australiana were extensively tested, because it 

 was one of the first to be examined, and the high toxicity of the 

 first sample compared with the other oils and with the crude oil 

 led to the belief that the disinfecting power might be due to a 

 constituent which accompanied the cineol during rectification, 

 and which might prove to be more efficient than phenol. A 

 second specimen of the rectified oil dispelled the idea. E. aus- 

 traliana was once known as E. amygdalina, but, owing to the 

 difference from the Tasmanian tree bearing this name, it was 

 renamed by Baker and Smith. The quality of the oil differs 

 according to the location of the tree. When growing on the 

 ridges of the Dividing Range at a high altitude, the quality of 

 the oil is poor compared with that obtained from trees growing 

 at a lower elevation.* 



The cineol had been obtained by freezing the rectified oil 



* In the latter case, the phellaiidrene (which is in fair amount in the oil 

 from the species growing at the higher altitudes, such as the Braidwood 

 district), lias practically disappeared, and the cineol has correspondingly 

 increased. The alteration in the percentage amount of the constituents 

 is only shown between the cineol and the pliellandrene. 



