1146. New and old plates.—­I have found voltaic batteries far more powerful when the plates were new than when they have been used two or three times; so that a new and an used battery cannot be compared together, or even a battery with itself on the first and after times of use.  My trough of twenty pairs of four-inch plates, charged with acid consisting of 200 water, 4-1/2 oil of vitriol, and 4 nitric acid, lost, upon the first time of being used, 2.82 equivalents per plate.  When used after the fourth time with the same charge, the loss was from 3.26 to 4.47 equivalents per plate; the average being 3.7 equivalents.  The first time the forty pair of plates (1124.) were used, the loss at each plate was only 1.65 equivalent; but afterwards it became 2.16, 2.17, 2.52.  The first time twenty pair of four-inch plates in porcelain troughs were used, they lost, per plate, only 3.7 equivalents; but after that, the loss was 5.25, 5.36, 5.9 equivalents.  Yet in all these cases the zincs had been well-cleaned from adhering copper, &c., before each trial of power.

1147.  With the rolled zinc the fall in force soon appeared to become constant, i.e. to proceed no further.  But with the cast zinc plates belonging to the porcelain troughs, it appeared to continue, until at last, with the same charge, each plate lost above twice as much zinc for a given amount of action as at first.  These troughs were, however, so irregular that I could not always determine the circumstances affecting the amount of electrolytic action.

1148. Vicinity of the copper and zinc.—­The importance of this point in the construction of voltaic arrangements, and the greater power, as to immediate action, which is obtained when the zinc and copper surfaces are near to each other than when removed further apart, are well known.  I find that the power is not only greater on the instant, but also that the sum of transferable power, in relation to the whole sum of chemical action at the plates, is much increased.  The cause of this gain is very evident.  Whatever tends to retard the circulation of the transferable force, (i.e. the electricity,) diminishes the proportion of such force, and increases the proportion of that which is local (996. 1120.).  Now the liquid in the cells possesses this retarding power, and therefore acts injuriously, in greater or less proportion, according to the quantity of it between the zinc and copper plates, i.e. according to the distances between their surfaces.  A trough, therefore, in which the plates are only half the distance asunder at which they are placed in another, will produce more transferable, and less local, force than the latter; and thus, because the electrolyte in the cells can transmit the current more readily; both the intensity and quantity of electricity is increased for a given consumption of zinc.  To this circumstance mainly I attribute the superiority of the trough I have described (1134.).