CHAPTER IV 

 INFLUENCE OF ELECTRICITY 



The influence of elecrticity upon microorganisms is much less than 

 one might perhaps expect, if the electriticy as such is considered. A 

 direct electric current passing through a nutrient medium will, of course, 

 cause electrolysis which is usually manifested by the formation of acid 

 on the positive pole and of alkaK on the negative pole. The acid and 

 alkali will kill microorganisms, as is discussed in the chapter on chemical 

 influences. In this case, it is not the electricity itself that destroys the 

 bacteria. It is also possible to kill bacterial cultures by passing an 

 alternating current through the medium for some time. No electrolysis 

 takes place in this case, still it is not the direct action of the current that 

 acts upon the organisms, but rather the heat produced by the current 

 passing through a medium of high resistance. If the culture is cooled 

 properly the influence of the current is insignificant if at all noticeable. 

 Whenever electricity is applied against microorganisms the effect is con- 

 sidered electrochemical. 



The electrical current is used in a very small way in the purification 

 of sewage. The sewage passes between two iron plates which represent 

 the two poles of a strong current. The electrical sterilization of milk 

 has been,patented. Wines are improved by electricity. The steriliza- 

 tion of drinking water by ozone is also an application of electricity, 

 though of course the ozone once formed by the current acts as a chem- 

 ical compound independently of its source, and the same effect would 

 be produced if the ozone were manufactured chemically. 



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