688 



tliiosiilphate, and then the potential fell to — 0,04 V., which was 

 about tlie initial ^•ahle. If we now compare the behaviour of the 

 Ni-electrode with this behaviour, we notice that the addition of the 

 ürst qiiantitj' of bromine has a smaller influence than foi' the bromine- 

 electrode, and that the addition of more bromine has a much greater 

 influence here than for the bromine-electrode. 



While the potential of the bromine electrode no longer changes 

 on further addition of Bromine up to 3 cm^, it increased for the 

 nickel-electrode by an amount of 0,34 V., so that the total rise 

 amounted to 0,95 V. 



And we see further that wliile the addition of KBr brought about 

 a decrease of only 0,04 Y. for the bromine-electrode, it came to 

 four times the amount, viz. to 0,16 V. for the nickel-electrode. 



All this suggests that the nickel-electrode does not behave at all 

 as a bromine-electrode in the experiments mentioned here, which is, 

 indeed, not astonishing, as the Br pretty strongly attacks the Ni-electrode. 



It is, therefore, clear that we have to do liere with a very parti- 

 cular behaviour of the metal itself, and that the explanation, as was 

 already surmised, must be this that during the action of bromine 

 on nickel a disturbance of the internal equilibrium takes place in 

 the meta! surface, in the nobler sense, and that this disturbance is 

 counteracted by addition of Br-ions, from which follows that bromine 

 ions execute a positively catalytic action. The result is that we have 

 observed here a great disturbance of the internal equilibrium in the 

 metal surface caused by chemical action, which proceeds continuously, 

 in the same direction as was found in case of anodic polarisation. 

 The electrolytical solution of metals is. however, very certainly the 

 most efficient means to disturb the internal equilibrium in the metal, 

 and thus in this way an anodic polarisation of 1 ,88 V. was observed 

 for Ni, v/hich after the current had been broken off still amounted 

 to 0,95 v., a value which is in fairly good agreement with that 

 found now. The disturbance brought about by Br during the rinsing 

 of the electrode with water being again neutralized, the previous 

 etching experiments with Br had a negative result. 



Chromium. 



Of all the metals which we have investigated up to now, chro- 

 mium is nearest akin to Ni. 



The following table represents the result obtained when bromine 

 was added to a rotating chromiumelectrode immerged in a Vio 

 N.OrClj-solution. 



