3 * 
Mr. Davy's Lecture on some 
VII. On the general Principles of the chemical Changes produced 
by Electricity 
The experiments of Mr. Bennet had shown, that many 
bodies brought into contact and afterwards separated, exhibited 
opposite states of electricity ; but it is to the investigations of 
Volta that a clear developement of the fact is owing; he 
has distinctly shown it in the case of copper and zinc, and 
other metallic combinations ; and has supposed that it also 
takes place with regard to metals and fluids. 
In a series of experiments made in 1801,* on the construc- 
tion of electrical combinations by means of alternations of 
single metallic plates, and different strata of fluids, I observed 
that when acid and alkaline solutions were employed as ele- 
ments of these instruments, the alkaline solutions always 
received the electricity from the metal, and the acid always 
transmitted it to the metal ; thus, in an arrangement of which 
the elements were tin, water, and solution of potash, the 
circulation of the electricity was from the water to the tin, 
and from the tin to the solution of potash ; but in an arrange- 
ment composed of weak nitric acid, water, and tin ; the order 
was from the acid to the tin, and from the tin to the water. 
These principles seem to bear an immediate relation to the 
general phenomena of decomposition and transference, which 
have been the subject of the preceding details. 
portion of oxygene and nitrogene gases : but neither of the foreign products, the 
nitrogene gas in the one case and the nitrogene and oxygene gases in the other, 
formed as much as 3% part of the volume of the gases ; and there is every reason 
to suppose that they were derived from the extrication of common air, which had 
been dissolved in the water. This result, which when I first obtained it in 1803, 
appeared very obscure, is now easily explained ; the alternate products must have 
been evolved at the points of the dissipation of the electricity. 
* See Phil. Trans. Vol. XCI. page 397. 
