1897.] Newly Prepared Gases. 369 



electrometer scale per minute. It did not vary in sign like the 

 charge on the hydrogen. 



(28) It is probable that the remarkable change of sign that 

 occurs in the charge carried by the hydrogen is due more to the 

 absorption of chlorine gas by the carbon electrode, than to the 

 presence of chlorine gas in the electrolyte ; for if the platinum 

 electrodes were used the hydrogen was given off with a large 

 positive charge and did not change when the chlorine got dissolved 

 in the electrolyte. 



It is improbable that the effect is due merely to the change 

 from platinum to carbon, as there was no corresponding change 

 when similar experiments were performed with sulphuric acid ; 

 the positive charge on the hydrogen evolved being large whether 

 platinum or carbon terminals were used and no change occurred 

 by running the current for half an hour, except a gradual increase 

 in the charge which can be shown to be due to a rise in tempera- 

 ture. It was also found that the charge on the hydrogen was 

 increased by using a new carbon electrode, instead of that used 

 with the hydrochloric acid. 



(29) In the case of direct electrolysis where no secondary 

 action takes place, or other chemical effects at the electrode, con- 

 siderations of polarization would lead us to expect that gases 

 would come off carrying with them a charge of the same sign, as 

 that which they carry in the electrolyte. Thus in the case of 

 polarization due to a layer of hydrogen with a positive charge 

 surrounding the electrode it is conceivable that, when the evolu- 

 tion of hydrogen takes place, some of the gas composing this layer 

 would come off without losing its charge. 



(30) In seeking to explain the chaDges of sign that occur, as 

 in the case of the hydrogen evolved from hydrochloric acid, it must 

 be remembered that, once the gas has acquired a charge, only a 

 small quantity of electricity is lost by bubbling through liquids, so 

 that causes which influence the sign of the charge should most 

 naturally be sought for at the place where the gas is being 

 evolved, and may be due to the state of the electrode or to 

 impurities in the electrolyte in the immediate vicinity of the 

 electrode. 



(31) There are some well known phenomena which point to 

 an explanation of the results obtained with hydrochloric acid, 

 namely: the electrification of gases by glowing metals*. The 

 typical effects of this kind are, the positive electrification of 



* J. J. Thomson, Phi J. Mag., Dec. 1896. 



