FORMALDEHYDE 51 



is not included here because it is seldom used in its 

 pure state since it is highly poisonous and destructive. 

 It is eminently efficient. 



Sulphur Dioxide. Sulphur dioxide is used for hos- 

 pitals, apartments, and ships. It is more efficient 

 when there is considerable moisture in the air. When 

 conditions are suitable for disinfection, anthrax bacilli 

 in the vegetative condition are destroyed in thirty 

 minutes when there is 1 volume per cent, of the gas 

 in the given space. "Four pounds of sulphur burned 

 for each 1000 cubic feet will give an excess of gas/ 5 

 Some water should be sprayed in the room or an open 

 vessel containing water should be there. It has been 

 suggested that the sulphur candles of commerce be 

 burned resting on a brick in a bucket of water. 



Dioxide of Hydrogen. A 2 per cent, solution of the 

 pure substance will kill anthrax spores within three 

 hours. In 20 per cent, solution it kills vegetative 

 bacteria, pus cocci and the like in a few minutes. Its 

 activity depends upon the liberation of free oxygen. 

 It should be kept tightly sealed, since it easily gives 

 up this gas. 



Formaldehyde. This is a gas, but is most commonly 

 seen as a solution ordinarily known under its trade 

 name formalin. This contains from 35 to 40 per cent, 

 of the gas and also some wood alcohol. The gas has 

 an affinity for many organic substances, among them 

 some of the dyes, but fabric is not affected. Of the 

 metals, iron and steel are attacked after long exposure 

 in the presence of moisture. By reason of its affinity 

 for organic substances it is a good deodorizer and 



