1873.] Messrs. Gladstone and Tribe on an Air-battery. 249 



Time after 



Expt. I. 



Expt. II. 



Oxygenized. 



Deo-xygenized. 



Oxygenized. 



De oxygenized. 



■ 



1 minute. 



78 



14 



130 



11 



4 minutes. 



72 



9 



90 



8 



12 „ 



G8 



6 



75 



6 



49 „ 







58 



3-5 



The contrast is evident. That the deoxygenized solution does give a 

 deflection at all is due partly to the difficulty of excluding air, and 

 partly, perhaps, at first to the oxygen condensed on the surface of the 

 silver plate. The effect due to the water itself is inappreciable. 



Erom the nature of the reaction it might be expected that the current 

 would gradually diminish on account of the using up of the dissolved 

 oxygen in the neighbourhood of the silver ; such a diminution always 

 does take place, at least after the first few vibrations of the needle. 



It might be expected, too, that when the amount of action has run down 

 considerably, the mere moving of the liquid so as to bring fresh parts of 

 the solution against the silver would augment the currents. It does so. 



The same might be predicted from stirring up the crystals of silver in 

 the tray so as to expose new surfaces. This also was found to be the case. 



And, again, it might be anticipated that if the wire were disconnected 

 for a time so as to allow the oxygen to diffuse itself from other parts of 

 the solution, and the connexion were made, the current would be found 

 as strong, or nearly so, as before. That also is true in fact. 



A cell with the plates connected by a wire was placed under a bell-jar 

 full of air over mercury. The mercury gradually rose inside, as might 

 be expected from the absorption of the oxygen in the air. 



The necessity of oxygen and the avidity with which it is taken up are 

 both illustrated b} r the following experiment : — Two cells with horizontal 

 plates were prepared alike in every respect, except that the first was 

 filled with a solution simply deprived of oxygen, the second with a 

 solution through which a stream of carbonic-acid gas had been passed 

 for some time. The first was placed in the air, the second in a vessel 

 from which the air had been expelled by allowing carbonic-acid gas to 

 flow into it for an hour or two. 



The deflections obtained were as follows, the 1-999 shunt being used 

 and the temperature being 13°'7 C : — 



YOL. XXI. 



x 



