INTERPRETATION 263 



solutions of KCl in mixtures of alcohol and water, but that the 

 quotient — decreases somewhat with increasing dilution. 



a^alc. H2O 



In the accompanying table (page 264) the values of — ll£^ ^j-e 



a^alc. H2O 



given for solutions of potassium caseinate (containing 80 X 10~^ 

 equivalents of base per gram, Cf. Table I) containing each of the 

 proportions of alcohol to H2O employed. 



It will be observed that the values of — ^^^ are appreciably 



a^alc. H2O 



constant, for each proportion of alcohol to water, for the solu- 

 tions containing to 60 per cent of alcohol, but that in the solu- 

 tions containing 75 per cent of alcohol the value of this ratio 

 does not even approximate to constancy but decreases rapidly. 

 There is, it is true, a slight but regular diminution in the value 

 of this ratio even in the solutions containing to 60 per cent of 

 alcohol, in passing from an equivalent concentration of neutral- 

 ized KOH of 0.0250 to 0.0016, but, except in the solutions con- 

 taining 75 per cent of alcohol, the diminution is not more than 

 a few per cent. 



We have seen (equations (ii) to (ix)) that the Ostwald dilution- 

 law, in the form expressed in equation (i) holds good, at any 

 rate for solutions of potassium caseinate in alcohol-water mix- 

 tures containing to 60 per cent of alcohol. 



From the symmetry of the equation: 



^ 1.037 X 10-^ 1.075 X 10-^ 2 



it would follow, were A strictly constant for all dilutions, that 

 the proportions of alcohol to water employed as solvent for the 

 caseinate affects only u -\- v, i.e., the migration- velocities of the 

 ions, and not the dissociation-constant (= K) or the number of 

 equivalents of caseinate resulting from the neutralization of one 

 molecule of KOH (= p).* Since the alteration in A with dilu- 

 tion of the potassium caseinate is so small for solvents containing 



* For, since x appears in one term of the equation as the first power, and 

 in the second as the square, if the ratio of — is constant any other 



^alc. H2O 



factor in the equation which is affected by the presence of alcohol must also 

 appear in the one term of the equation as the first power and in the other as 

 the square. 



