i86 Sterilization and Disinfection 



market. The "formalin," or 40 per cent, aqueous solution 

 of the gas, when fresh and tightly corked, is fatal to most 

 bacteria in dilutions of from 1:5000 to 1:25,000. Formal- 

 dehyd cannot be employed upon the skin or mucous mem- 

 branes because of its marked irritating effect. Care must 

 also be exercised that the hands do not become wet with 

 the concentrated formaldehyd solution, as it hardens the 

 skin and deadens sensation. 



It can be employed with advantage to spray the walls 

 and floors of rooms from a large atomizer, though Rosenau* 

 finds that unless the spray discharged be very fine its action 

 is uncertain. 



The original method of disinfection consisted of the evolu- 

 tion of the gas from methyl alcohol by volatilizing it in a 

 steam apparatus, and passing the vapor over a heated metal 

 plate. Shortly many efficient forms of apparatus were 

 placed upon the market for the evolution of the gas, or for 

 discharging it from the solution. 



The gas has enormous bactericidal powers, is not injurious 

 to man, and has no destructive effect upon furnishings. 

 Its penetrating powers are, however, limited, and its activity 

 greatly enhanced by moisture. 



It is not always necessary to use a special apparatus in 

 order to disinfect with formaldehyd; one can, in an emer- 

 gency, hang up a number of sheets saturated with the 40 per 

 cent, solution in the room to be disinfected. 



The number of sheets must vary with the size of the 

 room, as each is able to evolve but a certain amount of the 

 gas, and the quantity necessary for disinfection varies with 

 the size of the room. 



A better method of evolving the gas for purposes of 

 disinfection is to combine the solution with permanganate 

 of potassium, when an almost explosive liberation of the gas 

 takes place. 



The discovery of the efficiency of permanganate of potas- 

 sium for this purpose was made by Frankforter,t who found 

 that the best method of escaping the undesirable features of 

 the gaseous evolution was to mix the powder of permanganate 

 of potassium with an equal volume of sand. This brought 

 the formaldehyd solution more slowly into contact with 



* "Disinfection and Disinfectants," Philadelphia, 1902. 

 f "Reports and Papers of the American Public Health Association," 

 vol. xxxn, part 11, p. 114, 1906. 



