624: Mr. Bernard Cavanagh on 



Or if the lowest possible integers v l9 v 2 , ■ . • . be chosen 

 so' that 



Bnj : Sn 2 : 8n 3 : = v^ : v 2 : v 5 : 



we obtain, (for perfect solutes) from (57) 



2* a {<k— R[log c s - log (1 + m Q t Cl ) ] } =0, 



w 



hence 



lv s log c s - (%v s ) log (1 + m 2ci) =' ~ 2v s 5 



R 



= logK, . . . (59) 

 whereas the ordinary " mass-action equation " has been 



Xvslogc s = logK' (60) 



We see therefore that 



logK' = logKf (2v,)log(l + ™ 2<>i) . . (61) 

 or 



K'=K(1 + %£?!)**; . ... {62) 



or as long as m %Ci is small 



K / = K(l-hm Xc l tv s ) (63) 



We thus find that, except when Xv s is zero, the equilibrium 

 constant as hitherto written down should depend linearly 

 upon the total concentration o£ solutes present (whether 

 taking part in the reaction or not) if the participants in the 

 reaction are behaving as perfect solutes. 



The magnitude of the relative variation of K' is seen to 

 depend upon the magnitude of Wi^c^Vs compared with 

 unity. 



Now supposing for simplicity that the probable relative 

 error in the experimental determination of each of the 

 concentrations c s is uniformly equal to x, then the " probable 

 error ,} in K' is of course 



so the possibility of detecting the variation which we are 

 expecting in K' depends on the magnitude of 



2M 



(64) 



Since, as we have seen, for molar aqueous solution m^Ci is 

 probably at least '04, we find that evidence of the variation 

 we are considering will, in easily chosen cases, become 

 decisive as soon as the experimental error is reduced much 

 below one per cent. 



