EFFECT OF LARGE AND SMALL PLATES—SLMULTANEOUS DECOMPOSITIONS. 273 



power or electricity can pass. If in a particular case the most effectual number of 

 plates is known (1 151.), then the addition of more zinc would be most advantage- 

 ously made in increasing the size of the plates, and not their number. At the same 

 time, large increase in the size of the plates would raise in a small degree the most 

 favourable number. 



1155. Large and small plates should not be used together in the same battery : the 

 small ones occasion a loss of the power of the large ones, unless they be excited by 

 an acid proportionably more powerful ; for with a certain acid they cannot transmit 

 the same portion of electricity in a given time which the same acid can evolve by 

 action on the larger plates. 



1156. Simultaneous decompositions. — When the number of plates in a battery much 

 surpasses the most favourable proportion (1151 — 1153.), two or more decompositions 

 maybe eifected simultaneously with advantage. Thus my forty pairs of plates (1124.) 

 produced in one volta-electrometer 22*8 cubic inches of gas. Being recharged exactly 

 in the same manner, they produced in each of two volta-electrometers 21 cubical 

 inches. In the first experiment the whole consumption of zinc was 88*4 equivalents, 

 and in the second only 48*28 equivalents, for the whole of the water decomposed in 

 both volta-electrometers. 



1157. But when the twenty pairs of four-inch plates (1129.) were tried in a similar 

 manner, the results were in the opposite direction. With one volta-electrometer 52 

 cubic inches of gas were obtained ; with two, only 14-6 cubic inches from each. The 

 quantity of charge was not the same in both cases, though it was of the same 

 strength ; but on rendering the results comparative by reducing them to equivalents 

 (1126.), it was found that the consumption of metal in the first case was 74, and in 

 the second case 97, equivalents for the whole of the water decomposed. These results 

 of course depend upon the same circumstances of retardation, &c., which have been 

 referred to in speaking of the proper number of plates (1151.). 



1158. That the transferring, or, as it is usually called, conducting, power of an elec- 

 trolyte which is to be decomposed, or other interposed body, should be rendered as 

 good as possible*, is very evident (1020. 1120.). With a perfectly good conductor 

 and a good battery, nearly all the electricity is passed, i. e. nearly all the chemical ^ 

 power becomes transferable, even with a single pair of plates (867.) • With an inter-^ 

 posed non-conductor none of the chemical power becomes transferable. With an 

 imperfect conductor more or less of the chemical power becomes transferable as the 

 circumstances favouring the transfer of forces across the imperfect conductor are ex- 

 alted or diminished : these circumstances are, actual increase or improvement of the 

 conducting power, enlargement of the electrodes, approximation of the electrodes, 

 and increased intensity of the passing current. 



1159. The introduction of common spring water in place of one of the volta-elec- 

 trometers used with twenty pairs of four-inch plates (1156.) caused such obstruction 



* Gay-Lussac and Thenard, Recherclies Physico-Chimiques, torn. i. pp. 13, 15, 22. 



2 n2 



