KINETICS OF CERTAIN SILVER SALTS 279 



a galvanometer with direct reading. The Clark's cell being 

 introduced in the proper direction, it is well known that a 

 suitable resistance R may be introduced by means of the box, 

 which will put the galvanometer at rest at the point; when 

 this is effected, we have for the electrical intensity of the main 



E 



current i = >E denoting the electromotive force of the stand- 

 R 



ard Clark's cell. As the intensity of the current changed but 

 little and very gradually during the four or five hours which 

 were usually occupied by an electrolysis, we were satisfied 

 with making this measurement, which required but a few 

 seconds' attention, every ten minutes. The total amount 

 of electricity could then be integrated with sufficient cer- 

 tainty. 



Special experiments showed that, when resistance-box and 

 [111] Clark's cell were at a temperature of 18 C., the quan- 

 tity / of precipitated silver could be found by the formula, 



/ =^92.69, 



where T represents the duration of the electrolysis in minutes, 

 while r denotes the resistance which would have been neces- 

 sary to keep the galvanometer at 0, provided that amount 

 of electricity which actually passed through the apparatus 

 had done so in a current which remained constant throughout 

 this interval. Whenever the resistance-box and the cell were 

 at any other temperature, t, the above expression must be 

 multiplied with the factor 1-0.0012 (Z-18). This coefficient 

 of temperature, 0.0012, is derived from that of the cell, 

 -0.0008, and that of the box, +0.0004. 



Our battery consisted of 38 Leclanche cells, with a com- 

 bined electromotive force of about 40 volts and an internal 

 resistance of about 120 ohms. It furnished a current which 



