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LXXIII. On the Constant Voltaic Battery. By J. F. Danieia, 



Esq., For. Sec. U.S., Prof. Chem. in King's College, London ; 

 in a Letter addressed to R. Phillips, Esq., F.R.S., Sj-c. 



My dear Sir, 



IT appears from Professor Grove's letter, published in the 

 last Number of the Philosophical Magazine, that I was 

 under a misconception in supposing that he had derived his 

 battery from principles announced by me ; and that my me- 

 mory was treacherous in suggesting that I had heard him, at 

 a very crowded meeting of the members of the London Insti- 

 tution, admit (with a compliment which was impressive, but 

 doubtless much greater than the occasion required) that it 

 was in following up my train of reasoning that he was led to 

 the construction of the instrument whose wonderful powers 

 he was then about to illustrate. But waving this point of re- 

 collection, the error is certainly excusable, inasmuch as the 

 nitric acid battery exactly resembles the constant battery in 

 every particular except the substitution of platinum and ni- 

 tric acid for copper and sulphate of copper ; and an experi- 

 mentalist might, very obviously, have been led to the change 

 by following up the principle of diminishing contrary elec- 

 tromotive powers and resistances to a current originating with 

 the zinc. Professor Grove, however, states (although he 

 " cannot at this distance of time well describe what effect my 

 experiments had upon his mind ") that he cannot acquiesce 

 in the assertion that he was so guided ; but that the idea 

 which immediately led to the construction of his battery is 

 distinctly stated in the Phil. Mag. for 1839. The experiment 

 referred to, with two strips of gold leaf in nitric and hydro- 

 chloric acids, separated by a porous diaphragm, showing that 

 upon contact of the two strips the gold in the hydrochloric acid 

 was dissolved, is certainly a most beautiful one ; but the origin 

 of the force must be admitted to be at the junction of the two 

 acids; which, when a path for its circulation is opened, 

 react upon one another, and transfer by their polarization 

 chlorine to one electrode, and hydrogen to the other; the 

 former being taken up by the gold, and the latter by the nitric 

 acid. What this has to do with the nitric acid battery, in 

 which the two acids in contact are the nitric and sulphuric, 

 I really cannot perceive. The origin of the force in this case 

 has always appeared to me to be the action of the zinc upon 

 the dilute sulphuric acid, but Professor Grove may possibly 

 consider it to be still the contact of the two acids. He has, 

 however, stated that he was so led to the construction of his 

 battery, and X can have nothing more to say upon the subject. 



