Chemistry. — "On the Electro- Chemical Behaviour of Nickel." By 

 Prof. A. Smits and C. A. Lobry be Bruyn. (Communicated 

 bv Prof. S. Hoogewerff). 



(Communicated in the meeting of June 30, 1917). 



1. Nickel is a metal tliat assumes internal equilibrium exceedingly 

 slowly, and can therefore very easily be disturbed. When nickel, 

 immersed in a solution of NiSO, or Ni(N(),)j is made anode, resp. 

 cathode, a very strong polarisation is found already at very small 

 current densities. Also when attacked by chemical reagents as HNOg, 

 HjSO^ etc. nickel is very easily disturbed in noble direction. 



In a solution of NiSO^, which is in contact with the atmosphere, 

 nickel does not assume the equilibrium potential, simply because 

 the attack to which Nickel is subjected under these circumstances 

 by the air oxygen dissolved in the electrolyte, is sufficient to give 

 rise to a pretty great disturbance of the internal equilibrium in the 

 metal surface. That these small quantities of oxygen exert so great 

 an influence is owing to this that the oxygen is at the same time 

 a negative catalyst for the setting in of the internal equilibrium. 

 What is remarkable is this that not only oxygen but also hydrogen 

 has appeared to be a negative catalyst for this process, so that 

 nickel does not assume the equilibrium potential in a solution under 

 a hydrogen atmosphere either. 



2. These circumstances being unknown, the nickel potential has 

 always been measured in a hydrogen atmosphere or in air and it 

 was thought that in this way the equilibrium potential of this metal 

 was measured. Only Schoch has measured the nickel potential also 

 in vacuum, and found that it differs from that which is found in 

 a hydrogen-atmosphere. 



Led by the new considerations about the internal state and the 

 chemical and electromotive behaviour of metals, we have made some 

 experiments with the result that the behaviour of nickel, which is 

 still much more remarkable than we thought, can be explained in 

 an exceedingly simple way. 



To show this it is necessary to discuss the condition for the 

 hydrogen generation from a solvent containing hydrogen ions by 

 means of a metal (here nickel). 



