"The chemical reactions that take place in this couple are multiple.
In contact with a sufficiently concentrated solution of hydrate of
potassium or sodium, the chloride of silver, especially if it has been
recently prepared, passes partially into the state of brown or black
oxide, so that the carbon becomes covered, after remaining sufficiently
long in the exciting liquid, with a mixture of chloride and oxide of
silver. When the circuit is closed, the chloride becomes reduced to a
spongy metallic state and adheres to the surface of the carbon. At the
same time the zinc passes, in the alkaline solution, into a state of
chloride and of soluble combination of zinc oxide and of alkali.
"To avoid all loss of silver I cover the carbon with asbestos paper, or
with cloth of the same material, d. My piles are arranged in ebonite
vessels, A, which are flat, as in Fig. 1, or round, as in Fig. 2.
"In Fig 1 there is seen, at e, gutta-percha separating the zinc from the
carbon at the base.
"Under such conditions, we obtain a powerful couple that possesses an
electro-motive power of 1.5 to 1.8 volts, according to the concentration
of the exciting liquid.
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