428 UNPUBLISHED FRAGMENTS. 



We may regard -^- - as constant in integrating (for small y D ), which 



i/ ~* i 



gives p _ _^ Af yD 



-P-J-v At M 



At At PM S 



Now -r- - = ,7 = - ! nearly, which gives 



v u HU 



is Raoult > s Law< 

 m 



Raoult found values about 5 per cent, larger than this, which agrees 



At PM 



very well with the fact that - - is somewhat larger than - . It 



*y ~~ i) fft' 



is also to be observed that M D relates to the molecules in the solution, 

 but M 8 to the molecules -in the vapor. Or, with a coexistent vapor 

 phase of the solutum (alone or mixed with other vapors or gases), 

 we have 



41 



M-Q 



At 



B-B M 



~AT M '~ 



* -*- 



which makes 23L constant for the same solvent, solutum, and tern- 

 YD 



perature, according to Henry's Law. 



So for the galvanic cell which you first consider, I should write 



V -V' = a.(ff - /) = . log , 



1VL a ya 



ya> ya being the densities, supposed small, of the cation (a) in the two 

 electrodes, which are supposed identical except for the dissolved (a). 

 Here a a has reference to the solution and M a to the electrodes. It 

 may be more convenient to divide a a into the factors E a , a H , where 

 a H is the weight of hydrogen which carries the unit of electricity, and 

 E a the weight of (a) which carries the same quantity of electricity as 

 the unit of weight of hydrogen. In other words E a is Faraday's 

 " electrochemical equivalent " and a a is Maxwell's " electrochemical 

 equivalent." This gives 



M 

 where a n A is your R and -~ your v, v'* 



* [The valence of the ion]. 



