397 



that a reaction wliicli takes place at tlie hvdiogeii electrode is 

 reversed when Mg is replaced by zinc. 



KisTiAKOwsKY, however, riglifij comes to the following conclusion : 

 "Hieraus fogt iinmittelbar, dass die Mg bzw. Al. Eiectroden die 

 Eigenschaften von Gaselektrode hesitzen nnissen, d.h. ihr Ei, von 

 der Metaliionen-konzeMtration iinabhangig, dafur aber von der H' 

 nnd OH'-Konzentration abhangig sein mnss; ausserdem muss es, 

 wie bei Pt, von den rednzierenden Eigenschaften des Elektrolylen 

 abhangen." 



In this KisTAKOWSKY, however, qnife overlooked thai ilie behaviour 

 of an hydrogen electrode will also be found with any other metal, 

 if the boundary liquid consists of a saturated solution of the melal 

 hj'droxide. 



KisTiAKOwsKY, instead of measuring tiie Mg and H, potentials 

 in the same solution by changing (he Mg concentration, dipped his 

 Mg electrode, besides in a solution of MgSO^ and in a solution of 

 MgCl,, in different other solutions, no! containing Mg, and then 

 obtained results, of course, from which no conclusions al all can 

 be drawn. In iiis opinion, however, his results proved that the Mg- 

 potential is independent of the MgVconcentration. 



Beck ') was the first to demonstrate in his Thesis for the 

 Doctorate the invalidity of Kistiakowsky's views; he has also shown 

 experimentally that Mg never behaves as a hydrogen electrode. All 

 the same electromotive behaviour of Mg in MgSO^-solutions of 

 slight (H'j ) was not yet cleared up, for it appeared to him that the 

 difference in potential between the Mg and H electrodes in these 

 solutions of small H*-concentration increases with the Mg-concen- 

 tration. ') 



Beck found that the Mg electrode does not behave as a 

 hydrogen electrode, but the Mg does not behave as a normal metal 

 electrode either, for it was found tiiat the Mg-eleclrode becomes 

 more negative when the MgSO, -concentration increases. It further 

 appeared that on increase of the H'-concentration the Mg-potential 

 becomes more negative, and that it reaches a maximum negative 

 value for every MgSO^-concentration at a definite H'-concentration. 

 This maximum negative value vaiied with the MgSO, -concentration, 

 at least qualitatively, in a normal way. 



1) Rec. traT. chim. 41, 353 (1922). 



^) All the measurements were carried out by Beck in an atmosphere ot very 

 pure liydrogen, with vigorous stirring of the liquid, the Mg-electrode being at 

 rest If was found, that this way of stirring is much better than stirring by the 

 electrode it self. 



26* 



