DISINFECTION, STERILIZATION AND ANTISEPSIS. 255 



of the disinfectant, owing to the formation of the more ener- 

 getic sulphurous acid. 



For the destruction of insects, such as mosquitoes, this agent 

 is superior to formaldehyde. Its application for this purpose 

 is important in preventing the spread of ' yellow fever and 

 malaria. 



In practice, at least three pounds of sulphur per looo cubic 

 feet should be used, and moisture must be present. This latter 

 requirement can be fulfilled by evaporating several quarts of 

 water within the tightly closed room just prior to generating 

 the gas. In using powdered or flowers of sulphur, the neces- 

 sary amount is placed on a bed of sand or ashes in an iron pot, 

 which should be supported on some bricks in a pan or other 

 vessel containing an inch or two of water. The sulphur is 

 ignited by means of some glowing coals, or by moistening with 

 alcohol and applying a match. Difficulty is often experienced 

 in keeping the sulphur burning, and for this reason it is surer 

 and more convenient to use the so-called sulphur candles now 

 on the market. In operating with these, a sufficient number 

 are placed on bricks in a pan of water and the wicks lighted. 

 Liquefied sulphur dioxide may be used, and can now be ob- 

 tained in convenient tin receptacles containing a sufficient 

 quantity for the disinfection of an ordinary room. The can is 

 opened by cutting through a soft metal tube "projecting from 

 the top. The fluid vaporizes at the room temperature, and it 

 is simply necessary to place the pan in a convenient porcelain 

 dish and allow the fluid to evaporate. 



Sulphur dioxide is objectionable on account of its lack of 

 power when dry, and on account of its corrosive action on 

 metal and its bleaching effect on hangings and draperies in 

 the presence of moisture; it is, therefore, preferable to use 

 formaldehyde when possible. 



Chlorine. — A very active gaseous disinfectant, particularly 

 in the presence of moisture. An atmosphere containing i per 



