00 Dr. Beetz on the Electromotive Force of Gases. 



20*13 Platinum. Metals which do not decom- 



pose water. 

 '' 19'60 Sulphiiret of carbon. Camphor, volatile oils. 

 'i; 18*36 Olefiant gas. Olefiant gas. 



;. / ^ther, alcohol, sulphur. 



16*06 Phosphorus. Phosphorus. 



13*02 Carbonic oxide gas. Carbonic oxide gas. 

 3*82 Copper, 

 3'05 Sulphuretted hydrogen. 



Hydrogen. Hydrogen. 



+ 19*68 Zinc. Metals which decompose 



water. 

 The above results settle the question of dispute between 

 Grove* and Schoenbeinf, as to whether, in an oxy hydrogen 

 gas battery, the hydrogen alone, or both gases are active. The 

 opinion of the latter author is that the hydrogen alone produces 

 the current ; the presence of the oxygen would only then be 

 of use in lessening the charge of the free plate of platinum 

 produced by the current. Grove's experiments show that the 

 presence of air is necessary for the continuance of the current ; 

 for when the gas battery remained enclosed under a globe 

 filled with air, from which the oxygen was removed by 

 the combustion of phosphorus, the intensity of the current 

 sunk to 0, and on the admission of fresh air it gradually in- 

 creased. This experiment, which corresponds perfectly with 

 my experiments J upon ordinary hydrogen batteries. Grove 

 considers an argument against Schoenbein's view, and he is 

 certainly correct. That the increase in the current caused 

 by the oxygen is attributable to a diminution of the charge 

 is indisputable ; but it does not thence follow that the oxygen 

 exerts no electromotive action. According to the expe- 

 riments detailed above, the electromotive force of platinum 

 and hydrogen is =20*13; of platinum and oxygen =3*85; 

 the oxygen therefore contributes directly to the electric exci- 

 tation, but certainly much less than the hydrogen. Air, ni- 

 trogen, and nitrogenous compounds act with oxygen still more 

 feebly. The depolarizingaction of the oxygen cannot be taken 

 into consideration here, as the closure of the circuit is merely 

 momentary. 



As regards the situation of the electric excitation in the gas 

 battery, this was found by Grove § to be at the point of contact 

 of the platinum, gas and liquid. When the platinum did not 



* Philosophical Transactions, 1843, p. 98. [Phil. Mag., vol. xxiv. p. 346.] 



t Phil. Mag., vol. xxii. p. 165. 



X Poggendorff's Annalen, vol. Ixiv. p. 381. 



§ Philosophical Transactions, 1843, p. 97- [Phil. Mag., vol. xxiv. p. 276.] 



