346 GERMICIDAL ACTIVITY Of EUCALYPTUS OILS, ii., 



separate readily, and it is mure efficient than a 1:80 solution of 

 phenol. As it is at least five times inure effective than phenol, and 

 very much cheaper, it should find considerable use in spraying 

 rooms and in disinfecting' clothing ur such materials as are free 

 from oils ur fatty substances, in which the Eucalyptus oil is more 

 soluble than in water. The necessity for the use of water in con- 

 junction with the undiluted uils lias already been emphasised. 



Summary. — The Eucalyptus uils are irregular in their action 

 upon B. coli communis, and duplicate experiments may show a 

 considerable a mount of variation. 



Cineol begins to act in about a minute and a half; phenol acts 

 instantly. 



The curves of cineol and phenol cross in live minutes with a 

 dilution of 1 :75 at 20' J . 



The phenol coefficient of cineol in 15 minutes at 20° is 3-1; it 

 rises to 34 in 30 minutes, and then slowly declines to 2-8 in 1 hours. 



Aromadendral is the most active of the constituents of the oils. 

 The phenol-coefficient is 211 in 30 minutes. 



The next most active is piperitone (41), and possibly phellan- 

 drene. 



Pinene and sesquiterpene are low (0-8 to 0-5). 



The rectified oils of E. cinerea and E. Smithii are more efficient 

 than the crude oils. 



In the case of the oil of E. cinerea, this appears to be due to the 

 hydrolysis of the esters and the subsequent oxidation of the 

 alcohols to aldehydes. 



Treatment with alkali did not reduce the efficiency of the acicl, 

 rectified oil. 



The addition of acetic acid to the crude oil doubled the germi- 

 cidal power in the course of 3^ months. 



The germicidal activity of the rectified and crude oils of E. 

 cinerea is proportional to the starch-iodide reaction, and not to 

 the acidity, but this does not hold for the oils as a class. 



The rectified oil of E, polybractea is less efficient than the crude 

 oil. 



