Chemical Affinity in terms of Electromotive Force, 267 



formation of solutions of zinc and copper sulphates &c. of dif- 

 ferent densities through "migration of the ions/' thus indica- 

 ting considerable extents of non-adjuvancy. 



In order to obtain further information upon these points, a 

 large number of observations have been made upon various 

 forms of Daniell cell and allied combinations; the general results 

 of which are that, with the normal Daniell combination (zinc, 

 zinc sulphate, or dilute sulphuric acid, copper sulphate, copper), 

 the amount of non-adjuvant energy with suitable plate- surfaces 

 and with feeble rates of current-flow is insensible, but becomes 

 very considerable with more rapid rates of flow, or with certain 

 impure forms of metallic plate-surfaces — the non-adjuvancy 

 being partly due to incomplete development as E.M.F. of the 

 energy due to the solution of the zinc, but more especially to 

 the imperfect development as E.M.F. of that due to the trans- 

 formation of nascent into ordinary copper ; whilst the forma- 

 tion of solutions of densities different from those of the fluids 

 originally employed also contributes to the diminution in the 

 effective E.M.F. of the cell. With certain other forms of cell, 

 more or less non-adjuvancy exists under all circumstances. 

 In the following paper only those experiments referring to the 

 normal Daniell cell are described, the remainder being post- 

 poned to a later occasion. 



Experiments made to determine the total fall in E.M.F. through 

 so-called Polarization, occurring in variously arranged Daniell 

 Cells for definite amounts of increase in the rates of Current- 

 flow. 

 103. A gravity Daniell cell was constructed (fig. 1) with 



two zinc plates, A and B, supported so that 

 their upper surfaces were in the same hori- 

 zontal plane, by means of stout wires passing- 

 through an indiarubber cork, 0, the under 

 surfaces of the plates, and the wires between 

 the cork and plates, being covered with gutta 

 percha. This cork fitted into the lower end 

 of a wide glass tube some 4 or 5 centim. in 

 diameter and 12 or 15 long ; at the other end 

 was a precisely similar cork arrangement, D, 

 carrying two copper plates, E and F, of which 

 only the lower surfaces were uncovered with 

 gutta percha. The plates A and E were each 

 of such size as to expose precisely 2*5 square 

 centim. of surface, whilst the plates B and F 

 each exposed double that area. In order to 

 arrange the cell as a gravity battery, a con- 

 centrated zinc-sulphate solution (sp.gr. nearly 

 1*4) was run into the cell until half full, and 



Fig. 1. 



