1851 



ions and if it had remained so, the potential would have followed 

 the eui\e ABC, but now the iron is, indeed, in a liquid layer thai 

 is poorer in feni-ions than the li(|iiid outside the i)0undarj layer, 

 but the ferrions present prevent the iron from assuming internal 

 equilibrium, hence the potential cannot reach such a great negative 

 value as when the ferri-ious were present, as in the fust experinienl. 



Besides continually more feni-ions dilfuse into the boundary layer, 

 which causes the disturl)ance of the iron lo increase again and in 

 consequence of which the potential becomes again less negative. 

 When we imagine fig. 10 placed under fig. 2 of I he former publi- 

 cation, we get the schematic figure indicated jusi now. 



In this way the phenomenon for iron must be explaineil, and 

 very probably it will have lo be explained in the same way foi' 

 nickel and chromium. 



That for iro)i the minimum appears sooner and is more |)ronounced, 

 must be attributed to the great rapidity with which iron, so long as 

 it is not yet passive, tries to le-eslablish equilibrium after a disturb- 

 ance. Nickel is much more inert in a NiS04-solulioji than in a 

 NiCl, -solution, and this shows itself also again in this phenomenon '). 



3. When it now appears on continued research, as is to be 

 expected, that the discussed phenomenon can also be made to dis- 

 appear for nickel and chromium by beforehand heating the electro- 

 lytes with the metals in the form of powder for a long time in a 

 current of hydrogen, then it is sure that the solutions of nickel 

 sulphate and chromo-sulphate used up to now contain a second kind 

 of ions, and this in a concentration different from thai prevailing in 

 the liquid that coexists with the metal which is in internal equilibrium. 



For nickel we are theji confronted by the interesting question 

 what is the second nickel-ion here. 



Thus it will probai)ly appear that llie found [)henomenon furnishes 

 an excellent expedient lo decide whether a solution contains different 

 kinds of ions of a same elenient or wiiether it does not. 



In conclusion I will point out that it is very well possible that 

 as it were the refiected image of the found phenomenon can present 

 itself after calhodic polarisation; this has, however, not been found 

 by us as yet. The results published by Rahtkut would prove this 

 |)Ossibility for nickel, but in our opinion these results are not correct. 



Laboralory of General Anonj. CkeniUtry 

 of the (university. 



Amsterdam, March 27, 19Jy. 



') This will clearly appear in u folluwing communication. 



