DISINFECTANTS AND ANTISEPTICS. 20I 



Results of the earlier investigations seemed to show that for- 

 maldehyde possessed remarkably high germicidal properties, 

 but later experiments have failed to corroborate these. In solu- 

 tions of i-iooo an exposure of twenty-four hours is necessary 

 to destroy the Staphylococcus pyogenes aureus, while 1-5000 

 is sufficient to restrain its growth (Slater and Rideal). Its use 

 in a gaseous form as a house-disinfectant is by far the most im- 

 portant application at the present time. 



Harrington's investigations have shown that an atmosphere produced by 

 vaporizing 435 c.c. of formaUn (40 per cent, aqueous solution of the gas) in 

 1000 cubic feet of air space, equivalent to i quart to a room 15 feet square and 

 10 feet high, will destroy all exposed organisms in half an hour; when protected 

 by one fold of cotton-cloth, an exposure of one and one-half hours is necessary. 

 In a perfectly dry atmosphere the gas penetrates slightly, and will disinfect 

 through one layer of cotton-cloth; in a moist atmosphere no penetration can 

 be obtained. 



In vaporizing the gas many methods have been employed. 

 Simple evaporization of solutions without heat cannot be rcHed 

 upon, for the sohd, polymerized paraformaldehyde is easily 

 formed under these circumstances. Better results can be ob- 

 tained with the aid of heat, although polymerization is apt to 

 occur unless evaporation is rapid. To produce the best results 

 it has been found necessary to use special forms of lamps or 

 generators for its production, a few of which are mentioned 

 below. 



Sanitary Construction Company's Lamp. — This lamp consists 

 of a tank to hold the formaldehyde solution, and a spiral tube 

 by which the solution is slowly conducted through a flame and 

 vaporized. The necessary amount of solution is placed in the 

 tank and the apparatus started, outside the room, the gas being 

 conducted through the keyhole by a suitable tube. 



Trillat Autoclave. — This apparatus consists of a small silver- 

 Hned pressure-boiler, fitted with lamp, safety-valve, pressure- 

 gauge, thermometer, and escapement-tube. The necessary 

 amount of formaldehyde solution is placed within the apparatus. 



