•iJUtoAr. 



THE ^J 



LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[SIXTH SERIES.]/ -./ •»$ ^ 



MARCH 1907. 



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XXII. Chemical Effects of the Electric Discharge in rarefied 

 Hydrogen and Oxygen. By Rev. P. J. Kirkby, Fellow of 

 New College, Oxford*. 



IN the Philosophical Magazine for January 1905 1 described 

 the chemical effect o£ passing electricity through a mix- 

 ture of hydrogen and oxygen at low pressures and between 

 electrodes whose distance apart varied between *25 cm. and 

 1*5 cm. I explained the results by the hypothesis that the 

 gaseous ions as they pass from their origin to the electrodes, 

 break up into uncharged atoms those molecules of the gas 

 which they strike under favourable conditions, and thus set 

 the atoms free to group themselves afresh into molecules of 

 water-vapour. The experiments showed that when the cir- 

 cumstances of the discharge were constant, the number of 

 molecules of water was proportional to the quantity of elec- 

 tricity that passed and so to the number of ions which 

 reached either electrode, and was independent of the size 

 and material of the electrodes. The formula which approxi- 

 mately symbolized the results seemed to indicate that the 

 chemical combination was most intense within the region of 

 the cathode fall of potential, and that it went on to a smaller 

 extent elsewhere, though the discharge was too short to throw 

 this latter effect into relief. 



These conclusions were partly confirmed by some experi- 

 ments made with an apparatus wjiich will be described at the 



* Communicated by the Author. 

 Phil. Mag. S. 6. Vol. 13. No. 75. March 1907. Y 



