1906.] 



Action on Bacteria of Electrical Discharges. 



71 



apparent discrepancies in some of our results must be partly attributed. 

 For with variation in the amplitude of the electric current, which frequently 

 occurred in the course of our experiments, it was not possible to keep the 

 temperature of the emulsions at a constant point ; the most that we succeeded 

 in doing was to ensure by cooling arrangements that the temperature did 

 not rise to a point at which the direct germicidal effect of heat would come 

 into action. 



VI. — The Influence, on Bacteria Suspended in Water, of Nitrous and 

 Nitric Acids resulting from the Action of the Electrical 

 Discharge on the Am and taken up in Solution. 



We next proceeded to test the germicidal action of sterile distilled water 

 which had been exposed to discharges from the high-frequency apparatus 

 whilst contained in tubes under conditions similar to those which prevailed 

 in the experiments detailed in Table I. 



On adding iodide of potassium to distilled water which has been exposed 

 to the action of the discharge for a few minutes, a considerable amount of 

 iodine is set free, and further tests show the presence of nitrous and nitric 

 acids in solution. 



The immediate products of the action of the discharge on ordinary air 

 probably include ozone, hydrogen peroxide, nitrogen peroxide, and perhaps 

 other oxides of nitrogen. A certain amount of the substances thus formed 

 are taken up in solution by the water, and the ozone and hydrogen 

 peroxide are probably rapidly decomposed by reaction with the other 

 products present, nitric oxide being converted to nitrogen peroxide, and 

 nitrous to nitric acid. 



The nitrogen peroxide which is formed reacts with water to form nitrous 

 and nitric acids according to the equation 



2N0 2 + H 2 = HN0 2 +HN0 3 . 



Under the conditions of the experiment a part of the nitrous acid decom- 

 poses into nitric acid, nitric oxide, and water, 



3HN0 2 = HN0 3 + 2NO + H 2 0, 



and the nitric oxide would probably again be converted into nitrogen 

 peroxide and nitrous and nitric acids. 



Our experiments were carried out as follows : — After each tube had been 

 exposed to the action of the discharge for a given time the resulting acidity 

 was estimated in terms of nitric acid, and the germicidal action of the 

 solution was tested on a single species of bacterium. For the latter purpose 

 two loopfuls of growth from a culture on agar were rubbed up into an 



