84 



Mr. A. G. R Foulerton and Dr. A. M. Kellas. [Mar. 30, 



solution in considerable quantities after the exposure of the emulsion for as 

 short a period as 15 minutes. It is probable that under the action of the 

 discharge carbon dioxide is decomposed into carbon monoxide, oxygen,* and 

 possibly other products, and the hydrogen peroxide is then formed by the 

 action of the oxygen in nascent condition on the water vapour present. Some 

 other substance, which rapidly liberated iodine from iodide of potassium, was 

 also present in the solution, but starch iodide papers suspended in the tubes 

 above the emulsion gave no indication of the presence of ozone. 



It is perhaps worth mentioning that the colour of the discharge spark in an 

 atmosphere of carbon dioxide alters in appearance after the experiment has 

 been in progress for a few minutes. At first the spark presents a peculiar 

 green colour, but after a few minutes the appearance alters to that of a 

 combination of green with a very pale violet colour, so that often whilst the 

 upper part of the spark is of a distinct green colour the lower part appears to 

 spread out in the form of a fine network of violet rays. 



Experiments in an Atmosphere of Carbon Monoxide. 



One series of experiments in which the discharge from the alternator was 

 sprayed through an atmosphere of carbon monoxide on to emulsions containing 

 B. pyocyaneus and B. pvodigiosus respectively was carried out. 



The carbon monoxide was prepared by acting on sodium formate with con- 

 centrated sulphuric acid, and the gas was passed slowly from the gasholder 

 to another through tubes of the emulsions as they were being subjected to the 

 action of the discharge. In every experiment of this series the non-sporing 

 bacteria were destroyed after an exposure to the discharge for 30 minutes, 

 the current supplied to the motor driving the alternator being 5 amperes, and 

 the potential difference being 100 volts. In all these experiments, again, 

 peroxide of hydrogen was found to be present in some quantity after the 

 emulsion had been exposed to the action of the discharge for as short a period 

 as 10 minutes. According to Berthelot,f carbon dioxide and other products 

 are formed when a silent electrical discharge is passed through carbon 

 monoxide. 



Experiments in an Atmosphere of Nitrogen. 



Two series of experiments in which B. pyocyaneus and B. prodigiosus were 

 exposed to the action of the discharge in an atmosphere of nitrogen were 



* Compare results obtained by Collie on sparking carbon dioxide in vacuum tabes 

 (' Chem. Soc. Trans.,' 1901, p 1063). Also compare Berthelot (' Compt. Kend.,' 1898, 

 vol. 126). 



+ Loc. cit. 



