EFFECT OP CHEMICAL ENVIRONMENT 145 



ine. Eventually the chlorine goes into combination with 

 various bases and disappears in this form. The hypochlor- 

 ites are therefore disinfectants which act for a short period 

 of time only, after which their potency disappears. This 

 makes them exceptionally valuable for certain purposes, 

 but unreliable for others. The spore-producing bacteria are 

 relatively resistant to sterilization with hypochlorites. 

 Alkaline solutions of hypochlorites have also been used for 

 wound disinfection. Such, for example, is the Dakin's 

 solution used extensively in the sterilization of badly 

 infected war wounds. Potassium permanganate by its 

 direct oxidizing activity will completely destroy micro- 

 organisms in a comparatively short period of time. 



Essential Oils. — The essential oils of many spices and 

 other plants have considerable antiseptic power. Among 

 them may be mentioned oil of cloves, oil of cinnamon, oil of 

 mint and especially oil of eucalyptus. 



Stimulation of Disinfection.— The disinfecting action of 

 disinfectant in some cases may be materially increased by 

 the addition of other substances. For example, the addition 

 of alcohol to a solution of phenol materially increases the 

 rapidity with which it destroys microorganisms. Hydrogen 

 ions frequently increase the speed of disinfection. On the 

 other hand disinfecting action may be materially reduced 

 by the addition of certain substances. Sodium chloride, for 

 example, when added to mercuric chloride, decreases ioniza- 

 tion and correspondingly the rate at which microorganisms 

 are destroyed. 



Autogenic Products. — Substances produced by the 

 growth of microorganisms in culture media frequently not 

 only eventually stop their growth, but determine, in part at 

 least, the rate at which they die off. In short, bacteria are 

 usually eventually killed by products of their own growth. 

 In some cases this is due to the development of acids or 

 alkalies, but in many cases the substances produced are not 



