as 2.11, or for the
whole battery 84.4, equivalents. Similar results were obtained with my
battery of twenty pairs of four-inch plates (1129.). Hence it is evident
that the nitric acid was of great service when mingled with the sulphuric
acid; and the charge generally used after this time for ordinary
experiments consisted of 200 water, 4-1/2 oil of vitriol, and 4 nitric
acid.

1140. It is not to be supposed that the different strengths of the acids
produced the differences above; for within certain limits I found the
electrolytic effects to be nearly as the strengths of the acids, so as to
leave the expression of force, when given in equivalents, almost constant.
Thus, when the trough was charged with a mixture of 200 water and 8 nitric
acid, each plate lost 1.854 equivalent of zinc. When the charge was 200
water and 16 nitric acid, the loss per plate was 1.82 equivalent. When it
was 200 water and 32 nitric acid, the loss was 2.1 equivalents. The
differences here are not greater than happen from unavoidable
irregularities, depending on other causes than the strength of acid.

1141. Again, when a charge consisting of 200 water, 4-1/2 oil of vitriol,
and 4 nitric acid was used, each zinc plate lost 2.16 equivalents; when the
charge with the same battery was 200 water, 9 oil of vitriol, and 8 nitric
acid, each zinc plate lost 2.26 equivalents.

1142. I need hardly say that no copper is dissolved during the regular
action of the voltaic trough. I have found that much ammonia is formed in
the cells when nitric acid, either pure or mixed with sulphuric acid, is
used. It is produced in part as a secondary result at the cathodes (663.)
of the different portions of fluid constituting the necessary electrolyte,
in the cells.

1143. _Uniformity of the charge._--This is a most important point, as I
have already shown experimentally (1042. &c.). Hence one great advantage of
Dr. Hare's mechanical arrangement of his trough.

1144. _Purity of the zinc._--If pure zinc could be obtained, it would be
very advantageous in the construction of the voltaic apparatus (998.). Most
zincs, when put into dilute sulphuric acid, leave more or less of an
insoluble matter upon the surface in the form of a crust, which contains
various metals, as copper, lead, zinc, iron, cadmium, &c., in the metallic
state. Such particles, by discharging part of the transferable power,
render it, as to the whole battery, local; and so diminish the effect. As
an