818 



n$.z. 



circumstances as above the current efficiency was here SO'/o- The 

 metal had a greater tendency to scale off than that from chromic 

 acid and chromic sulphate. 



These electrodes were cemented into glass tubes, and six of them 

 were brought in a i-ul)ber stopper on tube A in figure 2. Tube A 

 was connected with lube D by means of a siphon 6', and tube D 

 by a siphon E with a saturate solution of potassium chloride, and 



further with a normal electrode. 

 The siphon E was closed on both 

 ends by a stopper of filtering 

 paper, and could further be en- 

 tirely closed by a cock. Through 

 the stopper of tube D passed a 

 bent capillary F, the lower end 

 of which was under mercury. 

 This gave an opportunity to the 

 liquid in A and D to expand. 

 The tubes A and D were quite 

 filled with a solution ofchromous 

 sulphate, and then closed by the 

 stopper-. In this way the solution 

 in A was perfectly shut off from 

 the air, and yet in conductive 

 cormection with the calomel 

 ''^ electrode. Altogether four tubes A 



were connected with D, which each contained six electrodes. 



6. Measurements of the Potential. 



Each of the tubes A contained two electrodes of chromium 

 according to Goldschmidt (1 and 2), two electrodes of electrolytic 

 chromium from chromic sulphate and chromic acid (3 and 4), and 

 two ot electrolytic chromium from chromic chloride (5 and 6). All 

 the potentials were measured with respect to a normal calomel 

 electrode. The solutions contained about 0.3 mol. Cr. SO. per L. 



On the whole the potentials presented the following course. When 

 the electrodes had been brought in contact with the' solution, the 

 values of the potential at first diverged greatly. When the solution 

 was feebly acid, the potential was about — 0.7 to — 0,8 Volt. In 

 neutral solution the potentials were mostly smaller negative, espe- 

 cially for the chromium according to Goi.uschmidt. Here the potential 

 was generally from — 0,2 to — 0,0. After a few days all the electrodes 

 of electrolytic chromium (3, 4, 5, and 6) reached, however, an 



