Chemical Force Affected by Dilution 285

version of the current took place.1 In 1828 De la Rive carried
these and similar cases much further, especially in voltaic com-
binations of copper and iron with lead.2 In 1827 Becquerel3
experimented with one metal, copper, plunged at its two ex-
tremities into a solution of the same substance (salt) of different
strengths; and in 1828 De la Rive4 made many such experi-
ments with one metal and a fluid in different states of dilution,
which I think of very great importance.

958. The argument derivable from effects of this kind ap-
peared to me so strong that I worked out the facts to some
extent, and think the general results well worthy of statement.
Dilution is the circumstance which most generally exalts the
existing action, but how such a circumstance should increase
the electromotive force of mere contact did not seem evident to
me, without assuming, as before (862), exactly those influences
at the points of contact in the various cases which the prior
results, ascertained by experiments, would require.

Fig. 72.

Fig 73-

959. The form of apparatus used was the bent tube already
described (903), fig. 70. The precautions before directed with
the wires, tube, etc., were here likewise needful. But there
were others also requisite, consequent upon the current produced
by combination of water with acid, an effect which has been
described long since by Becquerel,5 but whose influence in the
present researches requires explanation.

960. Figs. 72 and 73 represent the two arrangements of
fluids used, the part below m in the tubes being strong acid,
and that above diluted. If the fluid was nitric acid and the
platinum wires as in the figures, drawing the end of the wire
D upwards above m} or depressing it from above m downwards,
caused great changes at the galvanometer; but if they were
preserved quiet at any place, then the electro-current ceased,
or very nearly so. Whenever the current existed it was from
the weak to the strong acid through the liquid.

1 Annales de Chimie, 1823, xxii. p. 361. 2 Ibid. 1828, xxxvii. p. 234.
3 Ibid. 1827, xxxv. p. 120. 4 Ibid. 1828, xxxvii. pp. 240, 241.

5 Tratie de I'Electricite, ii. p. 81. and QErsted