490 Prof. H. P. Weber's Research 



es on 



was a very constant Daniel! possessing the electromotive force 

 1 1*02 x 10 lu [mgr.imm.§sec.~ 2 ] and the resistance 098 mer- 

 cury unit. The measuring-wire was a homogeneous one of 

 German silver 1 metre in length and with a resistance of 2*22 

 mercury units. In the circuit which included the measuring- 

 wire and the Daniell's element, there was moreover a rheostat 

 resistance amounting to 110 m. u.: so that the total resistance 

 of this circuit was 113*20 m. u. If \ denote the length of the 

 measuring-wire that must be inserted in order to effect com- 

 plete compensation, by the Daniell's element, of the electromo- 

 tive force E of the combination employed, then, under the 

 circumstances above described, the following equation holds 

 good: — 



E=\x 216-1 xlO 4 . 



The following values of \ were found: — For the combina- 

 tion of solutions 



A. 



Land n {S} 805 - 2 



La " dm {lui}'^ 



I. and IV. • {toIo} 794 - 5 



II. and III ( ?™'° !-288 



(288 

 II. and IV 1455"? 5- 



V 



>-a 



I 490 

 III. and IV il? 5 'i !>194 



88-9 \ 

 90-1 J 



f 195-11 

 1 194-0 J 



•o 



•o 



These observed values can be quite satisfactorily expressed, 

 through the concentrations z 2 and z 1} which appear at the ca- 

 thode and anode respectively of the combination employed, 

 by the parabolic formula 



\ = a[z 2 -z,][l + b(z 2 + z l )]. 



If, for example, we select the combination of solutions I. and 

 III. and that of solutions III. and IV., and calculate from the 

 values of A, found for these combinations, and from the respec- 

 tive concentrations, the constants a and b, we get 



a = 371-57, 



6= 0-782. 



From these we get, for the remaining four combinations, the 

 values of A: — 



304-5, 789-3, 290-5, 485-0, 



