taic
arrangement, there is an enormous waste of that power which it is the
object to throw into the form of an electric current; a consequence which
is put in its strongest point of view when it is considered that three
ounces and a half of zinc, properly oxidized, can circulate enough
electricity to decompose nearly one ounce of water, and cause the evolution
of about 2100 cubic inches of hydrogen gas. This loss of power not only
takes place during the time the electrodes of the battery are in
communication, being then proportionate to the quantity of hydrogen evolved
against the surface of any one of the zinc plates, but includes also _all_
the chemical action which goes on when the extremities of the pile are not
in communication.

998. This loss is far greater with ordinary zinc than with the pure metal,
as M. De la Rive has shown[A]. The cause is, that when ordinary zinc is
acted upon by dilute sulphuric acid, portions of copper, lead, cadmium, or
other metals which it may contain, are set free upon its surface; and
these, being in contact with the zinc, form small but very active voltaic
circles, which cause great destruction of the zinc and evolution of
hydrogen, apparently upon the zinc surface, but really upon the surface of
these incidental metals. In the same proportion as they serve to discharge
or convey the electricity back to the zinc, do they diminish its power of
producing an electric current which shall extend to a greater distance
across the acid, and be discharged only through the copper or platina plate
which is associated with it for the purpose of forming a voltaic apparatus.

[A] Quarterly Journal of Science, 1831, p. 388; or Bibliotheque
Universelle, 1830, p. 391.

999. All these evils are removed by the employment of an amalgam of zinc in
the manner recommended by Mr. Kemp[A], or the use of the amalgamated zinc
plates of Mr. Sturgeon (863.), who has himself suggested and objected to
their application in galvanic batteries; for he says, "Were it not on
account of the brittleness and other inconveniences occasioned by the
incorporation of the mercury with the zinc, amalgamation of the zinc
surfaces in galvanic batteries would become an important improvement; for
the metal would last much longer, and remain bright for a considerable
time, even for several successive hours; essential considerations in the
employment of this apparatus[B]."

[A] Jameson's Edinburgh Journal, October 1828.