VOLTAIC EXCITEMENT AFFECTED BY DILUTION. 
Ill 
2001. These, therefore, are jinally cases of such an inversion (1999.) ; but as the 
iron in the strong nitric acid acquires a state the moment after its immersion, which 
is probably not assumed by it in the weak acid (1843. 1951. 2033.), and as the action 
on the iron in its ordinary state may be said to be, to render it positive to the silver 
or copper, both in the strong or weak acid, we will not endeavour to force the fact, 
but look to other metals. 
2002. Silver and nickel being associated in weak nitric acid, the nickel was posi- 
tive ; being associated in strong nitric acid, the nickel was still positive at the first 
moment, but the silver was finally positive. The nickel lost its superiority through 
the influence of an investing film (1918.) ; and though the effect might easily pass 
unobserved, the case cannot be allowed to stand, as fulfilling the statement made 
(1999.). 
2003. Copper and nickel were put into strong nitric acid ; the copper was positive 
from the first moment. Copper and nickel being in dilute nitric acid, the nickel was 
slightly but clearly positive to the copper. Again, zinc and cadmium in strong nitric 
acid ; the cadmium was positive strongly to the zinc ; the same metals being in dilute 
nitric acid, the zinc was very positive to the cadmium. These I consider beautiful 
and unexceptionable cases (1999.). 
2004. Thus the nitric acid furnishes a most wonderful variety of effects when used 
as the electrolytic conductor in voltaic circles ; and its difference from sulphuric acid 
(1995.) or from potassa (1994.) in the phenomena consequent upon dilution, tend, in 
conjunction with many preceding facts and arguments, to show that the electromotive 
force in a circle is not the consequence of any power in bodies generally, belonging 
to them in classes rather than as individuals, and having that simplicity of character 
which contact force has been assumed to have, but one that has all the variations 
which chemical force is known to exhibit. 
2005. The changes occurring where any one of four or five metals, differing from 
each other as far as silver and tin, can be made positive or negative to the others 
(1997. 1998.), appears to me to shut out the probability that the contact of these 
metals with each other can produce the smallest portion of the effect in these voltaic 
arrangements ; and then, if not there, neither can they be effective in any other ar- 
rangements ; so that what has been deduced in that respect from former experiments 
(1829. 1833.) is confirmed by the present. 
2006. Or if the scene be shifted, and it be said that it is the contact of the acids or 
solutions which, by dilution at one side, produce these varied changes (1874. 1982. 
1991. 2014. 2060.), then how utterly unlike such contact must be to that of the 
numerous class of conducting solid bodies (1809. 1867.); and where, to give the 
assumption any show of support, is the case of such contact (apart from chemical 
action) producing such currents ? 
