J125 



cathodicallj polarised beforehand, lines 3 and 4 when this had been done. 

 This activating action of ti)e anodic polarisation still comes to 

 expression in a very pecnliar way in this, that for chi-omi inn on gold 

 a current [lotential line is fonnd with a retrogiessive part. With 

 increasing strength of the cnrrent, the potential descends. 



Snch a cnrrent potential line has been drawn in fignre JO. At 5 itiA 

 the potential is -|-0.94; this descends, on increase of (he strength 

 of the current to 100 niA, to -\- 0.82 V. This pecnliar course is 

 easily accounted for on the ground of what precedes. 



The electrode is activated 

 everv time at the breaking of 

 the current of the commutator, 

 ami that the more strongly as 

 the strength of the cui-rent is 

 the greater. 



In the period of time that 

 the electrode is currentless, the 

 potential is, therefore, niore 

 negative for a great strength of 



L 



potential. 



-0-Ï *a.s 



Fig. 10. 



current than for a small. Now in this method of procedure the 

 potential is not measured during the passage of the current, but 

 shortly after (about -^^ sec). 



That the current potential line is found to be retrogiessive, is 

 therefore again a consequence of the activation after anodic polari- 

 sation. When these considerations are true, this retrogressive line 

 will only be found when we work with a commutator, not when 

 we measure the potential with a siphon during the polarisation. 

 This proved actually to be the case. For chromium of Goldschmidt, 

 which likewise gives a retrogressive current potential line in solutions 

 of KCl, HjSO^ and HCl, when we work according to Lk Blanc's 

 method, a normal line was found when the potential was determined 

 by means of a siphon. 



Two lines have been 

 traced in figure 11 for 

 measurements with com- 

 mutator and with siphon 

 in HCl. The activation by 

 anodic polarisation appears 

 here very clearly. 



At 100 m A 'the potential 

 descends in y^ sec. from 

 4-1.22 V to +0.83 V, 



78* 



with commutator. 



with siphon. 



Fig. 11. 



