36 , GENERAL SCIENCE 



caustic may also be used. This method of sterilizing 

 is called cauterization. The hot iron is the cauter. 



(B) Germs and Chemicals. Besides sunshine, heat, 

 and air, man has learned to use a great number of chemical 

 compounds to fight his tiny enemies, the germs, which 

 are always ready to attack him at every opportunity. 

 More persons are killed in the fight with germs than in 

 all other wars, even if man does employ many weapons. 

 Some of the common disinfectants, or substances which 

 will kill germs, are: lime (unslaked), chloride of lime, 

 carbolic acid, sulphur, formalin or formaldehyde, mercuric 

 chloride or corrosive sublimate. Most of these are rank 

 poisons and must be used with care and caution. 



Air-slaked lime is of no value as a disinfectant, for it 

 will not kill germs. Lime slaked in water forms the 

 caustic lime which will destroy decaying matter as well 

 as bacteria. It can be used as a whitewash for barns, 

 animal pens, and outhouses, and when put on by a spray 

 pump will find the germs in all the cracks and corners. 

 As it is very cheap it can be used to disinfect wet places 

 and outhouses by scattering it about on the ground. 

 Carbolic acid can easily be mixed with the whitewash, 

 making it destructive to lice and other insects. 



Chloride of lime is a comparatively cheap disinfectant 

 because a small quantity can be made effective over a 

 very large area. A few pounds in a large street-sprinkling 

 tank will kill all the germs in the dust touched by the 

 water while sprinkling. It is also very effective in 

 garbage cans and water-closets. It has a strong odor of 

 chlorine, for chlorine gas is liberated when the chloride of 

 lime, or bleaching powder, is acted on by mild acids or 

 when it is exposed to the air. It destroys disease germs 

 by indirect oxidation. 



