water having suffered decomposition.

975. Sulphate of soda in solution was then experimented with, for the
purpose of ascertaining with respect to it, whether a certain electrolytic
intensity was also required for its decomposition in this state, in analogy
with the result established with regard to water (974). The apparatus was
arranged as in fig. 85; P and Z are the platina and zinc plates dipping
into a solution of common salt; _a_ and _b_ are platina plates connected by
wires of platina (except in the galvanometer _g_) with P and Z; _c_ is a
connecting wire of platina, the ends of which can be made to rest either on
the plates _a, b_, or on the papers moistened in solutions which are placed
upon them; so that the passage of the current without decomposition, or
with one or two decompositions, was under ready command, as far as
arrangement was concerned. In order to change the _anodes_ and _cathodes_
at the places of decomposition, the form of apparatus fig. 86, was
occasionally adopted. Here only one platina plate, _c_, was used; both
pieces of paper on which decomposition was to be effected were placed upon
it, the wires from P and Z resting upon these pieces of paper, or upon the
plate _c_, according as the current with or without decomposition of the
solutions was required.

976. On placing solution of iodide of potassium in paper at one of the
decomposing localities, and solution of sulphate of soda at the other, so
that the electric current should pass through both at once, the solution of
iodide was slowly decomposed, yielding iodine at the _anode_ and alkali at
the _cathode_; but the solution of sulphate of soda exhibited no signs of
decomposition, neither acid nor alkali being evolved from it. On placing
the wires so that the iodide alone was subject to the action of the current
(900.), it was quickly and powerfully decomposed; but on arranging them so
that the sulphate of soda alone was subject to action, it still refused to
yield up its elements. Finally, the apparatus was so arranged under a wet
bell-glass, that it could be left for twelve hours, the current passing
during the whole time through a solution of sulphate of soda, retained in
its place by only two thicknesses of bibulous litmus and turmeric paper. At
the end of that time it was ascertained by the decomposition of iodide of
potassium at the second place of action, that the current was passing and
had passed for the twelve hours, and yet no tr