DISINFECTANTS AND ANTISEPTICS. 203 



Formaldehyde Candles. — Mixtures of paraformaldehyde and 

 paraffin or other combustibles, which may be moulded into 

 candles, each enclosed in a tin case, make a convenient ap- 

 paratus to generate formaldehyde gas for room disinfection. 

 The candle is placed in a suitable fireproof dish, it is then ig- 

 nited, and generation of the gas is allowed to proceed in the 

 tightly closed room. 



Sulphur Dioxide. — This substance is used extensively for 

 house disinfection, and is usually prepared by burning sulphur. 

 Much difference of opinion exists regarding the value of it 

 as a disinfectant. The spores of anthrax are not killed by 

 several days' exposure to the liquefied gas. Anthrax and other 

 bacilli are destroyed in thirty minutes when exposed on moist 

 threads in an atmosphere containing one volume per centum of 

 the gas. An exposure of twenty-four hours in an atmosphere 

 containing four volumes per centum of the gas will destroy the 

 organisms of typhoid fever, diphtheria, cholera and tubercu- 

 losis. The presence of moisture greatly enhances the activity 

 of the disinfectant, owing to the formation of the more energetic 

 sulphurous acid. 



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

 is superior to formaldehyde. Its appUcation for this purpose 

 is important in preventing the spread of yellow fever and 

 malaria. 



In practice, at least 3 pounds of sulphur per 1000 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 necessar}' 

 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 con- 

 taining 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 



