be taken that no substance be
present that can act chemically on the gold. Although I used the metal
very carefully washed, and diffused through dilute sulphuric acid, yet
in the first instance I obtained gold at the negative pole, and the
effect was repeated when the platina poles were changed. But on
examining the clear liquor in the cell, after subsidence of the
metallic gold, I found a little of that metal in solution, and a
little chlorine was also present. I therefore well washed the gold
which had thus been subjected to voltaic action, diffused it through
other pure dilute sulphuric acid, and then found, that on subjecting
it to the action of the pile, not the slightest tendency to the
negative pole could be perceived.

547. In support of these arguments, it may be observed, that as yet no
determination of a substance to a pole, or tendency to obey the electric
current, has been observed (that I am aware of,) in cases of mere mixture;
i.e. a substance diffused through a fluid, but having no sensible chemical
affinity with it, or with substances that may be evolved from it during the
action, does not in any case seem to be affected by the electric current.
Pulverised charcoal was diffused through dilute sulphuric acid, and
subjected with the solution to the action of a voltaic battery, terminated
by platina poles; but not the slightest tendency of the charcoal to the
negative pole could be observed, Sublimed sulphur was diffused through
similar acid, and submitted to the same action, a silver plate being used
as the negative pole; but the sulphur had no tendency to pass to that pole,
the silver was not tarnished, nor did any sulphuretted hydrogen appear. The
case of magnesia and water (495. 533.), with those of comminuted metals in
certain solutions (546.), are also of this kind; and, in fact, substances
which have the instant before been powerfully determined towards the pole,
as magnesia from sulphate of magnesia, become entirely _indifferent to it_
the moment they assume their independent state, and pass away, diffusing
themselves through the surrounding fluid.

548. There are, it is true, many instances of insoluble bodies being acted
upon, as glass, sulphate of baryta, marble, slate, basalt, &c., but they
form no exception; for the substances they give up are in direct and strong
relation as to chemical affinity with those which they find in the
surrounding solution, so that these decomp