1133 



amounted to — 0.7 V in a saturate. KCl. solution, and no passivation 

 took place on anodic polarisation with 1.2 mA. Hence it appears 

 from this that cathodic polarisation activates the chromium less 

 strongly than treatment with hydrochloric acid. It appeared from 

 further experiments that cathodic polarisation J/;?imwAöó' the activity. ^) 

 Thus an electrode which had been in a solution of KCl for two 

 days, and had remained active in it, exhibited a potential of — 0.57 V, 

 On anodic polarisation with 0.3 mA the chromium remained active 

 with a potential of — 0.46 V. Then this electrode was cathodically 

 polarised with 50 mA for I7, hours. The potential was — 0.79 V 

 after interruption of the current, and rose to — 0.192 in V|^ hours. 

 Hence the activity had greatly diminished a/Ver cathodic polarisation, 

 which also appeared from this, that the electrode became passive 

 already on anodic polarisation with 0.01 mA in this case. 



On strong cathodic polarisation other electrodes obtained a much 

 more negative potential, down to — 1.22 V. Notwithstanding such 

 an electrode was strongly active as far as the values of the potential 

 are concerned, it could not withstand anodic polarisation with 0.1 

 mA without becoming passive. After activation in strong hydrochloric 

 acid the electrode easily resisted 0.4 mA, at which the potential 

 was — 0.55. 



4. Summary of the results. 



1. Electrolytic chromium becomes passive in chromous sulphate on 

 anodic polarisation with a sufficiently great strength of current. 

 After breaking of the current the potential of the electrode is more 

 negative than before the polarisation. 



2. When the polarising current is made stronger the potential 

 at first assumes a too positive value, which slowly falls to a more 

 negative value. When the current is made feebler, the same thing 

 takes place in reversed order. 



3. The activation to which chromium is subjected by anodic 

 polarisation, is the stronger as the electrode is polarized more 

 vigorously. 



4. GoLDscHiMDT Chromium, which has been activated by treatment 

 with molten ZnCl, or KCl -|- NaCl, can be anodically polarized in 

 a solution of KCl without becoming passive. The strength of current 

 which the chromium can resist in this, is greater when the current 

 is gradually slrengthened than when the strength of the current is 

 rapidly inci'eased. 



') This appears already from the experiment described on p. 1129. 



