l8o CHEMICAL INFLUENCES. 



it changes readily to H 2 O+ O, and this oxygen atom in the nascent state 

 is quite effective as an oxidizing agent. For an antiseptic, it must be used 

 in at least a i per cent solution, and for an absolutely reliable disinfectant 

 a still higher concentration is required. It loses its disinfecting property 

 easily because it is decomposed readily by the peroxidases of tissues and 

 organic liquids as blood, milk and pus. It is used in the preservation of 

 milk. Hydrogen peroxide is slowly decomposed by the katalase of milk 

 thus disappearing completely. 



Chlorine in its gaseous form is not used as a disinfectant, though its 

 germicidal power is quite strong. The so-called "chloride of lime," 

 manufactured by absorbing chlorine in slaked lime, gives in water 

 hypochlorite and free chlorine; these substances are good germicides 

 and chloride of lime is used in the disinfection of privy vaults, and other 

 places in which it may be employed without injury. 



Potassium permanganate is only incidentally used as a disinfectant. 

 Its chemical qualities prevent an ordinary use. 



Sulphurous acid, or sulphur dioxide (SO 2 ) was for a long time a 

 standard disinfectant and is still used occasionally for fumigating rooms, 

 stables, barns and out-buildings though it is substituted more and more by 

 formaldehyde which can be applied almost as easily. The burning of 

 sulphur is an extremely simple process, but it requires a moist air to dis- 

 infect properly, and under these circumstances it will attack metal, dyes 

 of clothing and even the fiber itself. 



