EFFECT OF VICINITY OF THE PLATES— FIRST IMMERSION— NUMBER. 271 



being 37 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, 217, 

 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. 



1 147. 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. Ficinity of the copper and zinc. — The importance of this point in the con- 

 struction 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, ac- 

 cording 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.). 



1149. The superiority oi double co/?/?er^ over single plates also depends in part upon 

 diminishing the resistance offered by the electrolyte between the metals. For, in fact, 

 with double coppers the sectional area of the interposed acid becomes nearly double 

 that with single coppers, and therefore it more freely transfers the electricity. Double 

 coppers are, however, effective, mainly because they virtually double the acting sur- 

 face of the zinc, or nearly so ; for in a trough with single copper plates and the usual 

 construction of cells, that surface of zinc which is not opposed to a copper surface is 

 thrown almost entirely out of voltaic action, yet the acid continues to act upon it and 

 the metal is dissolved, producing very little more than local effect (947. 996.). But 

 when by doubling the copper, that metal is opposed to the second surface of the zinc 

 plate, then a great part of the action upon the latter is converted into transferable 

 force, and thus the power of the trough as to quantity of electricity is highly exalted. 



MDCCCXXXV. 2 N 



