1127 



acts more strongly activating than sulphuric acid, with the same 

 concentration about three times as stronglj. Accordingly besides the 

 hydrogen ions, also the chlorine ions hav^e an activating action. 

 This follows also from this, that the strength of current of passivation 



Fig. 12. 



in hydrochloric acid to which potassium chloride has been added, 

 is greater than in hydrochloric acid alone. In two experiments this 

 amounted in O.J n HCl + n KCI to 14.5 and 16.5 mA, in 0.1 n HCl 

 to 5 and 7 mA. By making the concentration of the chlorine ions 

 ten times greater, the activating action is increased two and a 

 half times. 



The chlorine ions, however, do not act here independently of the 

 hydrogen ions, for in 1 n KCI without hydrochloric acid chromium 

 already becomes passive under ordinary circumstances with the 

 smallest strength of current. 



In the second place the anodic behaviour was investigated of 

 chromium that had been activated by placing it in melted salts. 

 The activating action of molten NaCl -f- KCI may appear from the 

 following experiment. 



A piece of chromium of Goldschmidt in a saturated solution of 

 KCI gave a potential of — 0.47 V, and already becanie passive at 

 0.1 mA. ^) After this electrode had been for half an hour in molten 

 NaCl + KCI, the potential was — 0.640. Now the electrode bore a 

 current of 8 mA without becoming passive on slow increase of the 

 strength of the current. 



1) These and the following experiments were not carried out with a commu- 

 tator, but the polarisation voltage was measured by means of a siphon, hence 

 during the polarisation. 



