38 



DESCRIPTION OF GALVANIC BATTEEIES. 



The remarks upon the economy of the arrangement just described 

 have reference to its use as an instrument, or separate battery, for 

 the deposition of a metal in a separate cell (decomposition cell); but 

 not to the arrangement known in electro-metallurgy as the single cell 

 process, which is simply a modification of one pair of Daniell's 

 arrangement ; a description of which, with its comparative economy, 

 will be given in another part of this treatise. 



Professor Daniell says that any depth of cell may be used accord- 

 ing to the power required, but this cannot be done with equal 

 advantage, for a large surface of zinc in a cell is not the most eco- 

 nomical, when great quantity of electricity is required. 



Grove's Battery. Another battery, constructed upon the same 

 principle as Daniell's, but differing in the arrangement of the metals, 

 and the substances used to excite them, was invented by Mr. GROVE, 

 and is known as Groves Battery. In this arrangement, platinum is 

 used instead of copper, and strong nitric acid instead of the sulphate 

 of copper of Daniell's battery. One pair may be fitted up con- 

 veniently in a tumbler or jelly-pot. A cylinder of zinc is placed 

 inside the tumbler ; within this cylinder is placed 

 a porous vessel, in which is a slip of platinum, 

 either in sheet or foil ; the porous vessel is filled 

 with strong nitric acid, and the tumbler with dilute 

 sulphuric acid : a wire is next attached to each 

 metal, and the battery is complete. When a 

 series of pairs is to be used, the form we have 

 found most convenient is to arrange the metals in 

 the same manner as we have described for Wol- 

 laston's trough (page 31.) The zinc is formed of 

 the same shape as shown by fig. 15. The zinc is placed in the 

 cell of the trough, and the porous vessel which should be flat is 

 placed within the zinc, so that the platinum in it may be connected 

 with the zinc of the neighbouring pair, as represented in figure 16. 



zzz, Are the zinc plates of 

 the form of figure 15. 



aaa, Porous cells filled with 

 nitric acid. 



occ, Plates of platinum united 

 to the zinc at top by binding 

 screws. 



pp, Are partitions. The divi- 

 sions of the battery trough need 

 not be water tight, but merely 

 such as will prevent the zincs 

 from touching one another. 



16. 



15. 



It will be seen that by this means any number of pairs may be 



