252 Messrs. Gladstone and Tribe on an Air-battery. [Apr. 3, 



the suboxide deposited on the silver was found to be equivalent to 

 0*398 grin, of metallic copper. This deposit of suboxide, though it soon 

 forms apparently a complete covering to the silver, does not greatly- 

 dimmish the action ; it is probably porous, besides being itself a conductor 

 of electricity. In some cases we have found it deposited in crystals 

 sufficiently large to be seen by the naked eye, and which are shown by a 

 magnifying-giass to be regular octaheclra. 



The internal resistance of this battery, as might be expected, is small. 



The electrolytic power of the current was examined. One cell, the 

 plates of which were about two inches in diameter, was found sufficient 

 to decompose such metallic salts as the nitrates of copper, silver, or lead, 

 copper sulphate or stannous chloride, in aqueous solution, when platinum 

 was used for the negative electrode, and for the positive the same metal 

 as existed in the salt experimented on. Six cells were sufficient to 

 decompose dilute sulphuric acid slowly and dilute hydrocloric acid pretty 

 quickly, copper electrodes being employed. 



The theoretical interest of this battery lies mainly in the fact that it 

 differs essentially from every other galvanic arrangement, inasmuch as 

 the binary compound in solution is incapable of being decomposed either 

 by the positive metal alone or by the two metals in conjunction ; it 

 cannot serve, in fact, as the liquid element of the circuit without the 

 presence of another body ready to combine with one of its constituents 

 when set free. 



Grove's gas-battery is essentially different from ours if the oxygen 

 and hydrogen condensed on the platinum plates play the part of the two 

 metals ; but it closely resembles ours if hydrogen acts the part of the 

 positive and platinum that of the negative metal ; the dilute sulphuric 

 acid, a hydrogen compound, will then be decomposed on account of the 

 simultaneous presence of the oxygen, which can combine with the 

 liberated hydrogen. Viewed in this manner Grove's gas-battery is only 

 a special case of the general reaction which we have described in our 

 previous paper ; and the formula will be : — 



Before contact, 



wPt + + H 2 S0 4 + ^H; 



after contact, 



mPt+H 2 + H 2 S0 4 + (n-2)H. 



The practical interest of our arrangement lies in the fact that it is 

 an approximation towards a constant air-battery. Should it ever come 

 into use elsewhere than on the lecture-table, it will probably be in the 

 form of a combination of zinc and copper, with an aerated solution 

 of zinc chloride ; for that arrangement has an electromotive force six 

 times that of the arrangement w T e have more particularly studied, and 

 about three quarters that of a Daniell's cell. The numbers representing 

 the difference of potential between the two metals, which were actually 



