BY R. i.KEK. SMITH. 3H) 



the three crude oils oi' the same species have their phenol-eoeffici- 

 euts inversely as their iodide of starch times. The acidities do not 

 show any such order. But when we take the oils as a whole, we 

 find that there is no relation, indeed in view of the high germicidal 

 power of aromadeudral, we are driven to the conclusion that the 

 chemical constituents of the oils, exclusive of any oxidising body, 

 are the sources of the germicidal substances, and determine the 

 disinfecting efficiency. The hydrolysis of the esters and the oxida- 

 tion of the resulting alcohols is undoubtedly the reason for the 

 enhanced efficiency of the older oils. 



As disinfectants, the rectified oils do not appear very promising. 

 The older oils of E. cinerea are certainly good, but those recently 

 distilled are not. The rectified oil of E. pplybractea is compara- 

 tively poor, while E. Smithii is good. 



With regard to the crude oils, the question of the price comes 

 in. Mr. If. G. Smith informed me that at the end of the year 1918, 

 the oils of E. cneorifolia, E. polybractea, and E. cinerea cost 

 from Is. to Is. 3d. per II). at the still. The oil of E. australiana, 

 Jst hour, cost fs. to fs. 2d., and of E. dice* and E. australiana 

 (Braidwood), 7d. to 8d. Rectification would add about 2d. per lb. 

 to these figures. Thus the two most effective crude oils, E. cneori- 

 folia and E. australiana (Braidwood) cost about fs. 3d. and 7^d. 

 each per lb. respectively. E. australiana (Braidwood) is thus the 

 cheaper, and, at the same time, the better disinfectant, ft is quite 

 a pleasant oil to work with, and, although containing phellandrene, 

 it has not the sticky character of the oil of E. dices. 



On account of the difficulty of maintaining an emulsion with 

 water, these oils will probably not displace the tar-products, which 

 are more easily emulsified when in strong dilutions. But there 

 are situations in which the use of the Eucalyptus oils would 

 be preferable. The disinfection of the walls of a room, for 

 example, by spraying, is a case in which a Eucalyptus oil, such as 

 E. australiana (Braidwood) could be recommended. The oil has 

 a phenol-eoellicient of 5 8, and a dilution of l:t>00, destroys B. c<>/{ 

 communis in half-an hour. An emulsion of, say, 1 :4(J(J does not 



