118 Dr. Faraday’s Experimental Researches in Electricity. 
also nearly pure, and one cubical inch dissolved 108 grains of 
marble. These were always mixed with water by volumes, 
the standard of volume being a cubical inch. 
1128. An acid was prepared consisting of 200 parts water, 
41 parts sulphuric acid, and 4 parts nitric acid ; and with this 
both my trough, containing forty pairs of three-inch plates, 
and four porcelain troughs, arranged in succession, each con- 
taining ten pairs of plates with double coppers four inches 
square, were charged. These two batteries were then used 
in succession, and the action of each was allowed to continue 
for twenty or thirty minutes, until the charge was nearly ex- 
hausted, the connexion with the volta-electrometer being care- 
fully preserved during the whole time, and the acid in the 
troughs occasionally mixed together. In this way the former 
trough acted so well, that for each equivalent of water decom- 
posed in the volta-electrometer only from 2 to 2°5 equivalents 
of zinc were dissolved from each plate. In four experiments 
the average was 2°21 equivalents for each plate, or 88°4 for the 
whole battery. In the experiments with the porcelain troughs, 
the equivalents of consumption at each plate were 3°54, or 
141°6 for the whole battery. In a perfect voltaic battery of 
forty pairs of plates (991. 1001.) the consumption would have 
been one equivalent for each zinc plate, or forty for the whole. 
1129. Similar experiments were made with two voltaic 
batteries, one containing twenty pairs of four-inch plates, ar- 
ranged as I have described (1124.), and the other twenty pairs 
of four-inch plates in porcelain troughs. The average of five 
experiments with the former was a consumption of 3°7 equiva- 
lents of zinc from each plate, or 74 from the whole: the average 
of three experiments with the latter was 5°5 equivalents from 
each plate, or 110 from the whole: to obtain this conclusion, 
two experiments were struck out, which were much against 
the porcelain troughs, and in which some unknown deteriorat- 
ing influence was supposed to be accidentally active. In all 
the experiments, care was taken not to compare zew and old 
plates together, as that would have introduced serious errors 
into the conclusions (1146.). 
1130. When ten pairs of the new arrangement were used, 
the consumption of zinc at each plate was 6°76 equivalents, or 
67°6 for the whole. With ten pairs of the common construc- 
tion, in a porcelain trough, the zinc oxidized was, upon an 
average, 15°5 equivalents each plate, or 155 for the entire 
trough. 
1131. No doubt, therefore, can remain of the equality or 
even the great superiority of this form of voltaic battery over 
the best previously in use, namely, that with double coppers, 
in which the cells are insulated. The insulation of the cop- 
