OF VITAL PHENOMENA 147 



The toxicity of the strong bases depends on the hydroxyl ion 

 concentration. These are seldom used for disinfection because 

 they are neutralized by the C0 2 of the air. Quick lime is used 

 more for its drying power and the toxicity of the Ca ions, than 

 for the toxicity of the OH ions. 



The weak bases are similar to the weak acids in that their 

 power of reducing the surface tension of water must be con- 

 sidered. Some of them, such as quinine and strychnine, are 

 especially destructive to certain protozoan parasites. 



Solutions of soap are alkaline, due to hydrolysis. Soap lowers 

 the surface tension of water enormously and has a marked 

 cytolytic action. It destroys the free forms of many bacteria. 



We may summarize some of the disinfectants as follows: 



Anesthetics. Alcohol, 50-70%. Phenol 5%, 24 hrs. ; Cresol 



5%, 2 hrs. 

 Oxidizers. H 2 2 1%, 30 min. Cl 2 ; Br 2 ; I 2 . 

 Reducers. Formaldehyde, S0 2 . 



Strong acids. 0.1 normal 15 minutes. 

 Weak acids. Acetic, concentrated. 

 Strong bases. Ca(OH) 2 (dehydrating). 

 Weak bases. Quinine. 

 Soaps. 

 Heavy metals. HgCl 2 ; Cacodylic acid AgNO s Argyrol; CuS0 4 ; 



Salvarsan. 



