755 



over the whole volume of the solution, w^e get 



V 



m r 



p RT a' 



^0 + - + — (1 + log c) - RTc + - 

 Q m m 



.(Zt-f 



tiVi . n . 



p RT a 



V'o + - 4- {I +logc) - RTc H- - 



da . 



When we take n again as constant, we get : 



ÖW, = 



771 . 71 e 



, 1 l\ RT c, 



^01 - ^'o. + P ( r - r 1 + — % - - RT{c,~c,) 



m 



when we denote the quanlilies referring to the anode hy the index 

 1, those referring to the catliode by the index 2. 

 We may further write : 



or, because 



^0 2 = Vol + ('' 



Ölpoi 



-^':) 



Ö. ' 



dv 



= —p, 



/I 1 



V%. = i?'oi +P 



VCi 9. 



There remains finally 



rf¥^ 



mil e 



.-.RT 



k 6 



'I c, 



(24) 



From the well known theorem for the free energy 

 we get with the aid of (10), (16), (20), and (24) : 



4:jr .X r 

 E=~^j {I-I,)dB- 



k.e 



TP - 







7n . n 

 k . s 



(25) 



RT . 



log {C, — C,) 



in which A is the electrochemical equivalent of iron. 



Hence the potential difference consists of two parts, \iz. one part 

 (the first two terms), which depends on the magnetic field, and a 

 second part, which depends on the concentrations at the electrodes. 

 The second term of the first part will increase proportional to the 

 second power of the external intensity of the field, the first term, 

 too, in case of small intensities of the field, where we may replace 

 (16) by (15); at great intensities of the field, however, ƒ will reach 



