266 DR. FARADAY'S EXPERIMENTAL RESEARCHES IN ELECTRICITY. 



1128. An acid was prepared consisting of 200 parts water, 4J 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 containing ten 

 pairs of plates with double coppers four inches square, were charged. These two bat- 

 teries were then used in succession, and the action of each was allowed to continue 

 for twenty or thirty minutes, until the charge was nearly exhausted, the connexion 

 with the volta-electrometer being carefully 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 decomposed in the volta-electrometer 

 only from 2 to 2*5 equivalents of zinc were dissolved from each plate. In four ex- 

 periments 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 con- 

 sumption at each plate were 3*54, or 141*6 for the whole battery. In a perfect vol- 

 taic 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, arranged 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 equivalents 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 1 10 from the whole : to obtain this conclusion, two experiments 

 were struck out, which were much against the porcelain troughs, and in which some 

 unknown deteriorating influence was supposed to be accidentally active. In all the 

 experiments, care was taken not to compare new and old plates together, as that 

 would have introduced serious errors into the conclusions (1146.). 



1 130. 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 com- 

 mon construction, in a porcelain trough, the zinc oxidized was, upon an average,^ 

 15*5 equivalents each plate, or 155 for the entire trough. 



1 131 . 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 coppers may 

 therefore be dispensed with ; and it is that circumstance which principally permits of 

 such other alterations in the construction of the trough as gives it its practical ad- 

 vantages. 



1132. The advantages of this form of trough are very numerous and great, i. It 

 is exceedingly compact, for 100 pairs of plates need not occupy a trough of more 

 than three feet in length, ii. By Dr. Hare's plan of making the trough turn upon 

 copper pivots which rest upon copper bearings, the latter afford fixed terminations ; 

 and these I have found it very convenient to connect with two cups of mercury, 

 fastened in the front of the stand of the instrument. These fixed terminations give 



