50 DESTRUCTION OF BACTERIA BY CHEMICALS 



Copper Sulphate. This chemical is potent against 

 typhoid in water in the presence of little organic 

 material in the strength of 1 to 400,000 in twenty- 

 four hours. 



Sodium Hydroxide (caustic soda). This substance is 

 very destructive to fabric and to the skin, but kills, 

 in the strength of 1 to 100, vegetative bacteria in a 

 few minutes, or spores are destroyed by 4 per cent, 

 solution in forty-five minutes. 



Sodium Carbonate. This chemical, advantageous for 

 boiling instruments, kills vegetative forms in 5 per 

 cent, solution very quickly, or spores in boiling water 

 in about five minutes. 



" Chloride of Dme" (chlorinated lime). This chemical 

 is also known as bleaching powder. There is a differ- 

 ence of opinion as to its composition. Its power de- 

 pends upon the liberation of free chlorine gas. It is 

 destructive to fabrics. It quickly degenerates and is 

 therefore to be used fresh. A 1 per cent, solution will 

 kill all non-spore-bearing organisms in five minutes, 

 and a 5 per cent, solution destroys spores in one hour. 

 Cakium hydroxide, made by adding water to quick- 

 lime, is efficient against typhoid bacilli in feces when 

 a 20 per cent solution is added to thoroughly mixed 

 feces in equal parts and exposed one hour. 



Acids. The strong mineral acids are not practical 

 disinfectants, but nevertheless, very efficient. Boric 

 acid kills the less resistant organisms in a 2 per cent, 

 solution, but only after some hours' exposure. 



Gaseous Disinfectants. There are only three of 

 practical value. They are sulphur dioxide, oxygen 

 from hydrogen dioxide and formaldehyde. Chlorine 



