1906.] Action on Bacteria of Electrical Discharges. 81 



Table VII. 



Cultures taken from 

 the bacterial emul- 



Quantity of peroxide of hydrogen in solution after exposure to 

 the discharge for 60 minutes. 



I. — One part in 15,000 (approxi- 

 mately) . 



II.— One part in 10,000. 



15 mins. 



30 mins. 



60 mins. 



15 mins. 



30 mins. 



60 mins. 





+ 



+ 



+ 



+ 



+ 



+ 





+ 



+ 



+ 



+ 



+ 









+ 



+ 



+ 















The results of these last experiments showed that when the discharge was 

 sparked on to distilled water through an atmosphere of hydrogen under con- 

 ditions similar to those prevailing in the experiments of Table V, except that 

 the platinum disc brush was used instead of the twisted wire brush, peroxide 

 of hydrogen was taken up in solution to the amount of 1 in 15,000, and 

 bacteria, which were subsequently immersed in the solution for as long as 

 60 minutes, were not apparently affected in any way. But when the dis- 

 charge was sparked on to the water whilst hydrogen was passing continuously 

 through it, under conditions similar to those prevailing in the experiments 

 of Table VI, the amount of hydrogen peroxide taken up in solution increased 

 to 1 in 10,000, and B. typhosus and B. coli communis were destroyed after 

 immersion in the solution for 15 and 60 minutes respectively. We were 

 unable to detect any change in the chemical composition of the water other 

 than that due to the presence of peroxide of hydrogen, and it was to the 

 presence of this substance that we attributed the germicidal action of the 

 solution. 



In comparing the results of the experiments of Tables VI and VII it must 

 be remembered that, as in the similar experiments with nitrous compounds, 

 the germicidal action of peroxide of hydrogen is most active when the sub- 

 stance is in the nascent condition. Thus Bonjean* found that the nascent 

 hydrogen peroxide liberated from calcium peroxide completely sterilised the 

 notoriously foul Seine water in four hours when acting in a dilution of 1 in 

 14,285, whilst a dilution of 1 in 3445, when obtained by means of a com- 

 mercial solution of hydrogen peroxide, did not sterilise the same polluted 

 water until it had acted for six hours. In the experiments of Table VI, 



* ' Comptes Eendus de l'Academie des Sciences,' vol. 140, p. 50, 1905. 

 VOL. LXXVIII. — B. G 



