54 DESTRUCTION OF BACTERIA BY CHEMICALS 



Dioxide of Hydrogen. A 2 per cent, solution of the pure 

 substance will kill anthrax spores within three hours. In 

 20 per cent, solution it kills vegetative bacteria, pus cocci 

 and the like in a few minutes. Its activity depends upon the 

 liberation of free oxygen. It should be kept tightly sealed, 

 since it easily gives up this gas. 



This substance has been widely used in the great European 

 war in the treatment of gas bacillus infection, its beneficial 

 effects being widely commented upon and attributed to the 

 liberation of oxygen in the tissues with bactericidal effect. 

 It seems to me that this cannot be all the reason, as this gas 

 is soon utilized by the tissues. A much more probable expla- 

 nation is that the liberation of bubbles tears the tissues into 

 large webbed meshes and allows other disinfectants free play 

 or permits a penetration of atmospheric oxygen inimical to 

 the anaerobic germs. 



Formaldehyde. This is a gas, but is most commonly seen 

 as a solution ordinarily known under its trade name formalin. 

 This contains from 35 to 40 per cent, of the gas and also some 

 wood alcohol. The gas has an affinity for many organic 

 substances, am6ng them some of the dyes, but fabrics are 

 not affected. Of the metals, iron and steel are attacked after 

 long exposure in the presence of moisture. By reason of its 

 affinity for organic substances it is a good deodorizer and 

 disinfectant chiefly because it forms new insoluble odorless 

 compounds. 



It is not very irritant when taken into the stomach, but 

 its vapors cause considerable annoyance in the eyes, nose, 

 and mouth. The lower animals resist it considerably, but 

 insects are not affected. It is more effective in the presence 

 of moisture and when the temperature is high, up to 120 F. 

 If these conditions cannot be obtained the exposure must be 

 longer. Two and one- half per cent, by volume of the aqueous 

 solution or 1 per cent, by volume of gas are sufficient to des- 

 troy fresh virulent cultures of the common non-spore-bearing 

 bacteria in a few minutes. 



