SOURCE OF ELECTRICITY IN THE VOLTAIC PILE. 
127 
the perpetual motion also be true ; and it would not be at all difficult, upon the first 
given case of an electric current by contact alone, to produce an electro-magnetic 
arrangement, which, as to its principle, would go on producing mechanical effects 
for ever. 
Royal Institution, 
December 26, 1839. 
Note. 
2074. In a former series (925, &c.) I have said that I do not think any part of the 
electricity of the voltaic pile is due to the combination of the oxide of zinc with the 
sulphuric acid used, and that I agreed so far with Sir Humphry Davy in thinking 
that acids and alkalies did not in combining evolve electricity in large quantity when 
they were not parts of electrolytes. 
This I would correct; for I think that Becquerel’s pile is a perfect proof that when 
acid and alkali combine an electric current is produced*. 
I perceive that Dr. Mohr of Coblentz appears to have shown that it is only nitric 
acid which amongst acids can in combining with alkalies produce an electric cur- 
rent -f-. 
For myself, I had made exception of the hydracids (929.) on theoretical grounds. 
I had also admitted that oxyacids when in solution might in such cases produce small 
currents of electricity (928. and Note .) ; and Jacobi says that in Becquerel’s im- 
proved acid and alkaline pile, it is not above a thirtieth part of the whole power which 
appears as current. But I now wish to say, that though in the voltaic battery, de- 
pendent for its power on the oxidizement of zinc, I do not think that the quantity of 
electricity is at all increased or affected by the combination of the oxide with the acid 
(933. 945.), still the latter circumstance cannot go altogether for nothing. The re- 
searches of Mr. Daniell on the nature of compound electrolytes^ ties together the 
electrolyzation of a salt and the water in which it is dissolved, in such a manner as to 
make it almost certain that, in the corresponding cases of the formation of a salt at 
the place of excitement in the voltaic circuit, a similar connection between the water 
and the salt formed must exist : and I have little doubt that the joint action of water, 
acids, and bases, in Becquerel’s battery, in Daniell’s electrolyzations, and at the 
zinc in the ordinary active pile, are, in principle, closely connected together. 
* Bibliotheque Universelle, 1838, xiv. 129. 171. Comptes rendu, i. p. 455. Annales de Chimie, 1827, 
xxxv. 122. 
t Philosophical Magazine, 1838, xiii. p. 382; or Poggendorf’s Annalen, xlii. p. 76. 
1 Philosophical Transactions, 1839, p. 97. 
