1130 



Jdst as HiTTORF has found, it appeared also in these experiments 

 that chromium is more strongly activated by molten zinc chloride 

 than bj molten KCl + NaCl. 



In molten K, Or, ().. and also glowed at the air, chromium becomes 

 very little activated, but yet it is a little more active than chromium 

 that has not been heated. In molten KCN the metal is perceptibly, 

 though feebly activated, it bore 1.5 uiA without becoming passive. 

 It is remarkable that not always the electrode that has the most 

 negative potential in currentless condition, is made passive with the 

 greatest difficulty. Thus chromium that had been iuimersed in molten 

 KCN presented a potential of — 0,44 V before |)olarisation, after 

 polarisation — 0.58 V. Yet this chromium was less easy to make 

 passive than chromium from molten K, Cr, ()., which showed 

 — 0.56 befoie polarisation, — 0,64 V after polarisation. 



All the electrodes that had been treated with molten salts, were 

 covered witti a layer of green or black oxide. From molten ZnCl, 

 and KCl -|- NaCl the metal generated hydrogen. The chromium that 

 had been glowed at the air, exhibited blue annealing colours. 



The treatment that the chiomium electrode has been previously 

 objected to, is therefore of great influence on the passifiability. 



The same thing applies to the concentration of the solution in 

 which the chromium is examined. 



The metal is very easy to 

 make |>assive in a solution of 

 Na,S()<, not so easy in a solu- 

 tion of KCl. 



In this the strength of current 

 of passivation is the greatei- as 

 the KCl-content of the solution 

 is the greater. Figure 14 repre- 

 sents the line of passivation for 

 a same chromium electrode in 

 a saturated solution of potassium 

 chloride, and in a 0,1 n solution. 

 When an electrode that has 

 bpen activated in molten ZnCl,, 

 is anodically polarized with a sufficient density of current, it becomes 

 passive, and presents potentials which are the same as for an 

 electrode which has lain in nitric acid beforehand for a long time, 

 and has become passive through this. After the current has been 

 broken off, the electrode from ZnC.l, becomes again active after a 

 short time, that from HNO, remains passive. Also an electrode 



Fig. 14. 



