663 
c=0.001 and a is 6, the limiting current is 0.95 x the limiting 
AE 
current for the same anhydrous ions, and al ; 199° FSG. “thie 
value without hydration. 
Though the determination of the current potential line supplies us 
with a means for the determination of the hydration of the ions, 
this means will only be serviceable when we succeed in carrying 
out the determination of the current potential line very accurately. 
Theoretically this method may be put on a line with the method 
followed by BvcrBöckK'), Wasnsurn*) and others, where the degree 
of hydration is derived from an indirect determination of the 
quantity of water liberated at the cathode. According to equation 
(21) we find here the hydration of the cation alone, whereas 
Bucupéck and Wasxpurn’s method furnishes the difference of the 
products of hydration and mobility of cation and anion. 
When we polarize anodically with a current density equal to the 
cathodic limiting current, we get: 
Mis Sean == Fr EEC). EELT ae ae 
Hence we have 
sek C 
for the value of hydration and concentration assumed above, whereas 
we have c, = 2C without hydration. 
Hence the influence of the hydration appears to be slight also at 
the anode. 
Some special cases present themselves with the anodic polarisation 
when the metal ion can form a sparingly soluble compound with 
one of the present anions as for solutions of the most complex salts, 
for electrolysis of solutions of halogenides with a silver anode ete. 
In some cases it is desirable to prevent the formation of the sparingly 
soluble solution, as in the electrolysis of solutions of complex cyanides, 
in other cases it is desired that the compound is deposited on the anode, 
e.g. in the electrolytical determination of the halogens, and some- 
times too it is desirable that the compound separates in the liquid, 
namely in the method of Lückow ®) for the electrolytical formation 
of metal compounds. 
In virtue of the above considerations it is now possible to give 
the conditions on which the process will take place in one way or 
another. 
1) Z. f. physik. Chemie 55 (1906) 563. 
2) Jahr. d. Radioaktivität 5 (1908) 493, 6 (1909) 69. 
3) Z. f. Elektrochemie 3 (1897) 482, 
