THEORY OF CONCENTRATED SOLUTION: 



H5 



must give a rough measure of the stability of the compound 

 formed. But the relative stability of a series of acid salts in the 

 presence of excess of water should be proportional to the 

 " strength " of the different bases. Hence the order of stability 

 of the bisulphates should be KHSO,, NaHSt) 4 , NH 4 HS0 4 , 

 Mg(HS0 4 )» Zn(HS0 4 ),„ Cu(HS0 4 ) a . It will be observed that 

 this is precisely the order of stability as deduced from the curves 

 given by Holmes and Sageman. [See Fig. 6.] 



Putting the number of mols of bisulphate proportional to 

 the expansion ( 8), on mixing we have 



x — p h 

 and substituting in the mass action equation for x we obtain 

 For y = 0.25 (0.25— .269 p) ( 0.75 — .269 p) = A." X (0.269/-'/). 

 For y = 0.5 (0.5— .394/O (-5— -394 P) = ^X (0.394) Y 

 From these two equations p = 0.82 



Similarly the experimental expansions for other values of y 

 can be used to obtain a value of p. Were there no experimental 

 errors p would always have the same value. The value of p as 

 deduced from all the measurements given for the system under 

 consideration is not quite constant, but very nearly so. The 

 mean value of /> is very near 



p = 0.80 



Substituting for p we obtain the following values for K : — 



y = 0.2 0.25 0.33 0.5 0.67 0.75 

 K = 0.29 0.40 0.34 0.34 0.32 0.29 



Mean K = 0.33. 



When one considers the cumulative effect of any experi- 

 mental error on the value of K the constancy attained above is 

 quite satisfactory. It shows that the process causing the expan- 

 sion on mixing, whatever its nature, is governed by the law of 

 mass action in the form set down. 



Taking the mean value of K, and re-calculating x for the 

 different mixtures, we obtain the following numbers : — 



Fraction mols 



K.,SO i in the 



mixture 



Fraction 



mols 

 KHSO, 



Calculated Expan- ' , 



„:,._ „ Holmes experimental 



multiplied by 

 30400 



/ah 



for the Expansion 



