DISINFECTANTS AND ANTISEPTICS. 209 



room should then be made as nearly airtight as possible; this 

 can be accomplished by pasting strips of paper over registers, 

 cracks, spaces between window-sashes and the Hke. Form- 

 aldehyde gas is then passed through the keyhole into the room 

 (or it may be generated by formaldehyde candles) in sufficient 

 quantity to destroy the infectious element. The room should 

 be sealed for at least twelve hours, after which time it may 

 be opened and aired. The process is completed by washing 

 all exposed surfaces in the room with i-iooo bichloride of 

 mercury. This latter requirement is not essential if the gas- 

 eous disinfection has been complete, but since we have no 

 absolute knowledge on this point, the secondary washing should 

 be carried out. This method can be considered reliable for 

 surface disinfection, but for the interior of mattresses and 

 stuffed furniture-cushions it is not certain. In all cases where 

 absolute disinfection is demanded, such articles must be ripped 

 apart and loosely exposed to the gas. They may be disposed 

 of by fire or steriHzed by steam under pressure. The latter 

 method must necessarily be a matter of municipal control, 

 and can be carried out only by means of suitable apparatus 

 in the hands of a municipal disinfecting corps. Instead of 

 formaldehyde, sulphur dioxide may be used for room disin- 

 fection, but in the light of present knowledge the formaldehyde 

 method is superior. 



