OXIDISING SUBSTANCES 767 



There is some ground for connecting the disinfectant 

 action of metallic salts with a reducing action on some 

 forms of protoplasm, as pointed out by Loew. 



The permanganates have considerable germicidal power 

 when in strongly acid or alkaline solution, but the readi- 

 ness with which they are affected by organic substances 

 makes them unsuitable for practical use. Peroxides and 

 ozone are open to the same objection, arid have less disin- 

 fectant power. Hydrogen peroxide is much used in 

 surgery, also in the Budde process for sterilising milk 

 (p. 740), and ozone has been practically applied in the 

 sterilisation of water-supplies (p. 724), and attempts 

 have been made to utilise it for the disinfection of 

 wounds. Acetozone also slowly liberates ozone. 



Organic substances. The methane and the aromatic 

 series furnish the disinfectants which are most important 

 in practice. 



Alcohol itself possesses some disinfectant power for 

 sporeless organisms, but only when absolute or in very 

 strong solution. 



Formaldehyde is by far the most important of the 

 methane group. It can be applied either as a solution 

 (formalin) or as gas. The gas can be produced by the 

 incomplete combustion or oxidation of methyl alcohol, 

 by the evaporation, with or without pressure, or spraying, 

 of formalin, either alone or mixed with calcium chloride 

 or glycerin, by the depolymerisation by heat of the solid 

 polymer paraformaldehyde, or by mixing this substance 

 with potassium permanganate. Many forms of apparatus 

 have been designed for the production of formaldehyde gas 

 for disinfection. In an^ form the gas seems to give little 

 more than superficial disinfection, and to require precau- 

 tions to ensure diffusion throughout the atmosphere of a 

 room.. The conditions desirable for disinfection by form- 

 aldehyde gas are saturation of the air with moisture, 



