The rendering of these couples is considerable; the small cells shown
in Figs. 1 and 2 give about two amperes in short circuit; the large
one gives 16 to 20 amperes. Two of these elements can replace a large
Bunsen cell. They are remarkably constant. We may say that with a
depolarizing surface double that of the zinc the battery will work
without notable polarization, and almost until completely exhausted,
even under the most unfavorable conditions. The transformation of the
products, the change of the alkali into an alkaline salt of zinc, does
not perceptibly vary the internal resistance. This great constancy is
chiefly due to the progressive reduction of the depolarizing electrode
to the state of very conductive metal, which augments its conductivity
and its depolarizing power.

The peroxide of manganese, which forms the base of an excellent
battery for giving a small rendering, possesses at first better
conductivity than oxide of copper, but this property is lost by
reduction and transformation into lower oxides. It follows that the
copper battery will give a very large quantity of electricity working
through low resistances, while under these conditions manganese
batteries are rapidly polarized.

The energy contained in an oxide of copper and potash battery is very
great, and far superior to that stored by an accumulator of the same
weight, but the rendering is much less rapid. Potash may be employed
in concentrated solution at 30, 40, 60 per cent.; solid potash can
dissolve the oxide of zinc furnished by a weight of zinc more than
one-third of its own weight. The quantity of oxide of copper to be
employed exceeds by nearly one-quarter the weight of zinc which enters
into action. These data allow of the reduction of the necessary