152 DR. B. D. STEELE, DR. D. McINTOSH AND DR. F, H. ARCHIBALD 



This is the case, for example, in an aqueous solution of ammonia, to which reference 

 will be made later. 



If, however, we assume that two or more molecules of AB unite to form a compound 

 which undergoes ionic dissociation, AB itself being unable to conduct the current, 

 then the molecular conductivity may decrease with dilution whether the solvent 

 enters into the composition of the electrolytic compound or not. 



If we consider the two cases : 



(1) A compound of n molecules of solute with m molecules of solvent is formed 

 according to the equation 



n (AB) +m (CD) ^ (AB). (CU) mf 

 the active masses being 



a b and c. 



Then, if we again consider sufficiently dilute solutions, b may be regarded as 



constant, and 



ka n = k'c or c = Ka". 



If ionic dissociation occurs so that a* of the compound is ionised, then, as before, 

 the ionic concentration = pa.c = paKa*. 

 The specific conductivity 



K = pVaKa" = aK'a" (2). 



The molecular conductivity 



a = - = aKV- 1 . 



a 



and since the dilution 



V = - 



a' 



K = aK'V-", 

 or 



cV- = aK'. 



* In the development of this relation no .assumption has been made us to the nature of the ionisation 

 of the electrolyte. 



If we consider the second case, for example, there are a number of ways in which the compound A,,B,, 

 can ionise. 



Thus Q 



(1) A n B, t 7-*- ABn-i + B. 







(2) AA-^Att + 

 and generally 



(3) A n B n -^-AA 



If dissociation takes place according to the first of these equations, 2 ions result from the dissociation 

 of 1 molecule of the electrolyte. 



If according to the second equation, the number of ions is (n+1), and, generally, the number is (r+l). 



Now whatever value r may have, the number of ions present is given by a (r+l) and is therefore 

 proportional to a. 



