Prof. R. Bunsen's Spectral-Analytical Researches, 4<27 



of zinc theoretically required for current-production in the con- 

 nected battery is dissolved in the battery when unconnected, 

 and that only a part of the metal dissolved in the latter case is 

 employed for current-production in the former. These facts are 

 the more worthy of remark when it is remembered that the che- 

 mical processes accompanying the solution of zinc are altogether 

 the same in the open as in the closed battery ; in neither case 

 does polarization take place on the zinc plate. 



These facts are entirely in keeping with the view which regards 

 solution of zinc not as the cause, but as a necessary condition of 

 the current. The numbers in column VI. express, in percent- 

 ages of the total quantity of zinc dissolved per hour, the propor- 

 tion of zinc lost, i. e, not used in current-production. The 

 amount of zinc thus lost, amounting to about 22*5 per cent., 

 remains tolerably constant during the exhaustion of the battery. 

 The amount of nitric acid which passes through the clay cell of 

 the Grove or carbon-zinc battery by endosmotic action is but 

 small; with an amalgamated zinc plate of 156 square centims. 

 surface in contact with sulphuric acid diluted with fifteen times 

 its weight of water, the amount of zinc hourly lost amounted to 

 only 0*3 grm.j in practice this might be overlooked. On the 

 other hand, the best-constructed batteries, made on the above 

 principles, when employed for the production of long-continued 

 currents, show a very considerable consumption of zinc, depen- 

 dent upon the formation of the current, and brought about by 

 the electrolytic carrying over of nitric acid. In order to arrive 

 at a knowledge of the amount of zinc lost in these batteries as 

 compared with the loss in a chromic-acid battery, a small volta- 

 meter was placed in the connecting-circuit of a four-pair carbon- 

 zinc battery : the loss of weight in the voltameter, which was 

 connected with a calcium-chloride tube in order to keep back 

 water vapour, was determined after the mixed gases had been 

 replaced by dry ah*. The level of the nitric acid in the clay 

 cells (which were new and of the best quality) stood somewhat 

 under that of the sulphuric acid in the zinc cells; the capacity 

 of the clay cells was 120 cubic centims., of the zinc cells 250 

 cubic centims., and the active amalgamated zinc surface encom- 

 passing the clay cylinders extended to 156 square centims. 



If w be the amount of water, in milligrammes, decomposed in 

 the voltameter during t seconds of time, z the loss of weight, in 

 milligrammes, suffered by each of the four zinc cylinders during 

 the decomposition, and a the electrochemical equivalent of water 

 = 0*009421, then the mean current-intensity during the experi- 

 ments is found in B.A. units by the equation 



T— w 



J -7t ; 



