370 Mr Townsend, Electrical Properties of [Nov. 22, 



oxygen when a metal is being oxidized, and the negative electrifi- 

 cation of hydrogen when blown past a hot oxidized metal ; the 

 metal in the former case uniting more readily with the negative 

 oxygen atoms, and the oxygen in the latter uniting more readily 

 with the positive hydrogen atoms. The only necessity for the 

 high temperature of the metal is to break up some of the 

 molecules of the gas into atoms, but in the cases we are dealing 

 with the gases, at the electrode, are already in the atomic state. 

 We should therefore expect somewhat similar effects to take place 

 when the gases which are evolved can form chemical compounds 

 with the electrode, or with bodies either dissolved in it, or in its 

 immediate vicinity. 



(32) If the above principles are applied to the case of hydro- 

 chloric acid we should expect, when the gases are evolved by 

 electrolysis, that the hydrogen would carry a positive charge, and 

 the chlorine a negative charge. The subsequent change from 

 positive to negative, in the case of the hydrogen, can be explained 

 by supposing a small quantity of hydrochloric acid to be formed 

 at the negative electrode, due to the action of the nascent 

 hydrogen on the chlorine, and that the positive hydrogen atom is 

 more active in forming a compound with chlorine than the nega- 

 tive. A similar explanation would apply to the change which 

 occurs from negative to positive in the charge carried by the 

 chlorine when platinum is used instead of carbon for an electrode, 

 since a chloride of platinum is formed. 



(33) The charged hydrogen given off from a platinum elec- 

 trode, in the electrolysis of hydrochloric acid, has the same 

 property of forming a cloud when bubbled through water as the 

 highly charged gases obtained by other methods. The chlorine 

 however has only a small charge, and moreover contains a quantity 

 of hydrochloric acid vapour which would be difficult to remove, 

 without making the charge too small to form a visible cloud. 

 The hydrogen was treated in the following manner, in order to 

 get rid of the acid vapour which would form a cloud when bubbled 

 through water. The delivery tube from the cell was connected to 

 the tube T^ which dipped into a strong solution of caustic potash 

 contained in a flask H x , and the gas then passed along a tube 

 containing glass wool soaked in caustic potash before it bubbled 

 through the water in a flask H 2 . The hydrogen which was 

 evolved from the platinum electrode, after passing through this 

 apparatus, was led into an insulated inductor connected to the 

 electrometer and, with 10 amperes through the electrolyte, the 

 spot of light on the electrometer scale was deflected 37 divisions 

 per minute, and with 14 amperes, 62 divisions per minute, the 



