Comparative Poiuer of some Disinfectants. 99 



floating about, or resting on walls or other surfaces. On a 

 small scale, and where the conditions approximate those of 

 the experiments just detailed, the ozonic ether may therefore 

 be used with advantage. 



IV. — Experiment with Chlorine. 



The general impression in recent times is that chlorine 

 does not deserve the great reputation it formerly enjoyed as 

 a disinfectant, and, indeed, experiments have tended to show 

 that when the gas is dry it has little or no power as a bleach- 

 ing agent or as a parasiticide. I made one experiment in 

 which the bacterialised paper was exposed, in a wooden box 

 with a loosely-fitting lid, to the gas, evolved in the usual 

 way by adding a few drops of muriatic acid to chloride of 

 lime. The chloride of lime was rather damp, and a good 

 deal of moisture was carried up with the gas. Three pieces 

 of the paper were left suspended in the box for 1, 3, and 4 J 

 hours respectively. The solution containing the 1 hour 

 piece became milky in 4 J days, the other two remaining 

 quite clear. 



It appears then that, used in the manner described, 

 chlorine, though not equal to sulphurous acid, is more 

 powerful than carbolic acid. As ordinarily used, however, 

 it can serve no good purpose, and sprinkling small quanti- 

 ties of chloride of lime on floors and other surfaces, in the 

 hope of aflecting any contagious matters floating in the air, 

 must reaUy be regarded as mere trifling. 



V. — Experiments with Dry Heat of 212° Fahr. 

 These may not have very much value ; but as I have not 

 met with similar ones, they may be given for what they are 

 worth. In the absence of any more elaborate scientific 

 armamentarium, I adopted the following procedure : — Two 

 short, wide-mouthed bottles were carefully washed and then 

 heated strongly in an oven, so as to ensure the removal of all 

 moisture and the destruction of any organisms which they 

 might by chance have contained. When still warm a piece 

 of the bacterialised paper was put into each, and a good 

 plug of baked cotton inserted into the mouth, which was 

 further covered with a cap of the same material. They 

 were then immersed in water, which was kept boiling for 

 noted periods. The paper lying flat on the bottom of the 



