electrical and chemical changes. 393 
tain and influenced by the state of the condenser and the 
atmosphere. 
IV. On the electrical and chemical effects exhibited by combinations 
containing single metals and one fluid. 
I know of no class of phenomena more calculated to give 
just views of the nature of electro-chemical action than those 
presented by single metals and fluids ; and as their results 
are, with one or two exceptions, entirely new, I shall describe 
them with some degree of minuteness. When two pieces of 
the same polished copper, connected with the platinum wires 
of the multiplier, were introduced at the same time into the 
same solution of hydro-sulphuret of potassa, there was no 
action ; but if they were introduced in succession, there was 
a distinct and often, if the interval of time was considerable, 
a violent electrical effect — the piece of metal first plunged in 
being negative, and the other positive. 
This result depends upon the circumstance of the produc- 
tion of a new combination, which is negative with respect to 
the metal ; for after the formation of the sulphuret of copper, 
the plate of copper that has been first plunged into the solu- 
tion exhibits the same negative state with respect to polished 
copper, whether introduced into saline solutions, or alkaline 
or acid menstrua. The electrical effect therefore does not 
depend on so simple a condition as would at first appear, 
and it may be in fact referred to the combinations containing 
two metallic substances and one fluid. 
The grey sulphuret of copper is negative, in solutions of 
hydro-sulphuret, to clean copper, and the superficial coating 
has apparently similar electrical powers to this substance. 
