'2 Faraday's Researches

ifo ^eil^t^1' Still there were great variations in degree; thus
acM \ri S^on& ac*d was oruy a little positive to silver in weak

u.cid' r *r°n *n wea>k ac^ was very Pos^ve to s^ver m strong

])o *"* . nerau7 the metal, usually called positive, was most

ositive in the weak acid; but that was not the case with lead,

tln> and zinc.

.
^W0 meta^s in strong and weak nitric acid. — Here the

Rree of change produced by difference in the strength of the
« cid was so great as to cause not merely difference in degree,

I lnversions of tne order of the metals, of the most striking
nature. Thus iron and silver being in tube No. 2 (962), which-
ever metal was in the weak acid was positive to the other in the
**rong acid- It was merely requisite to raise the one and lower
™ other metal to make either positive at pleasure (963).
Copper in weak acid was positive to silver, lead, or tin in strong
acid. Iron in weak acid was positive to silver, copper, lead,
2inc, or tin in strong acid. 'Lead in weak acid was positive to
coppery silver, tin, cadmium, zinc, and iron in strong acid.
Silver in ^weak acid was positive to iron, lead, copper, and,
though slightly, even to tin in strong acid. Tin in weak acid
was positive to copper, lead, iron, zinc, and silver, and either
neutral or a little positive to cadmium in strong acid. Cadmium
in weak acid is very positive, as might be expected, to silver,
Copper, lead, iron, and tin, and, moderately so, to zinc in the
strong acid. When cadmium is in the strong acid it is slightly
positive to silver, copper, and iron in weak acid. Zinc in weak
acid is very positive to silver, copper, lead, iron, tin, and
radmium in strong acid: when in the strong acid it is a little
positive to silver and copper in weak acid.

985. Thus wonderful changes occur amongst the metals in
circuits containing this acid, merely by the effect of dilution;
*o that of the five metals, silver, copper, iron, lead, and tin, any
one of them can be made either positive or negative to any other,
with the exception of silver positive to copper. The order of
these five metals only may therefore be varied about one
hundred different ways in the same acid, merely by the effect
of dilution.

986. So also zinc, tin, cadmium, and lead; and likewise zinc,
tin, iron, and lead, being groups each of four metals; any one
of these metals may be made either positive or negative to any
other metal of the same group, by dilution of this acid.

987. But the case of variation by dilution may, as regards thefferent order from that which they have in acid uniform