96 Comparative Power of some Disinfectants. 



paper not disinfected had been put became opalescent, it 

 was evident that the bacteria in it were alive (in the sense 

 that a dried seed is alive) at the time the experiment was 

 carried on. No experiment was held to be satisfactory unless 

 both of these tests were fulfilled. 



The endeavour was made to apply the disinfecting process 

 in such a way as to allow of the results attained being made 

 a guide in the practical use of these agents in every-day life; 

 and in the use of vapours the time required for destroying 

 the bacteria was the point investigated, the concentration 

 being that which could be attained by the usual simple 

 methods. 



I. — EXPEEIMENTS WITH CAEBOLIC AcID. 



A wide-mouthed 8-oz. bottle was used, about a dram of 

 crystallised carbolic acid being put into the bottom of it. 

 The pieces of paper were suspended from a hook on the 

 under side of the cork, which was fixed tightly in, and the 

 whole left at the ordinary temperature of the atmosphere for 

 carefully noted periods. A good deal of time was lost in 

 feeling my way, in the absence of any knowledge at the time 

 of similar observations. 



(1.) Two pieces of the paper were exposed to the carbolic 

 vapour for 9 hours and then introduced into the solution. 

 In both cases opalescence began to appear in 42 hours, show- 

 ing that the bacteria had not been destroyed; though as the 

 phial into which undisinfected paper had been put began to 

 be coloured in 36 hours, it appeared as if some of them had 

 been killed, or at least in some way paralysed. 



(2.) Two pieces exposed to vapour for 19 hours. Both 

 remained clear. 



(3.) One piece each 11 and 14 hours. Both remained clear. 



Suspecting now that the air contained in the bottle had 

 not had time to become saturated with the carbolic vapour 

 in No. 1, which was begun as soon as the crystallised acid 

 had been put into it, and in view of the positive efiect in 

 Nos. 2 and 3, I next tried some shorter periods. 



(4.) One piece each exposed to the vapour for periods of 

 2f, 3J, 5, and 7 hours. The first two became opalescent, 

 whilst the others remained quite clear. This experiment I 

 considered quite conclusive, as the opalescence began to 

 appear in the following order : — With the undisinfected 

 paper in 60 hours, with that exposed for 2| hours in three 



