CONCENTRATION OF ALCOHOL 



259 



computed are observed to be appreciably constant and equal 

 to ten times the log to base 10 of A in the above equation. The 

 average value of A for all of the determinations enumerated in 

 Table I (omitting, in the computation, the solutions containing 

 75 per cent alcohol) is 1.0265. For the various concentrations 

 of potassium caseinate the values of A are as follow : 



TABLE III 



In the accompanying table (Table IV) the experimental values 

 of X and those computed from the formula 



Xo 





are compared. Two "calculated" values of Xy are given, the 

 first calculated value of Xy being computed from the average 

 value of A for the given concentration of caseinate, the second 

 being computed from the average value of A for all the deter- 

 minations enumerated in Table I, with the omission, of course, 

 of those for the solvent containing 75 per cent of alcohol. 



The same relation also holds good for solutions of ''neutral" 

 potassium caseinate, that is, for solutions which contain 50 X 10~^ 

 equivalents of base per gram and are neutral to litmus instead 

 of, as in the experiments cited above, 80 X 10~^ equivalents of 

 base per gram (neutral to phenolphthalein). Two and a half 

 per cent solutions of casein in 0.0125 N KOH were prepared, 

 containing 0, 10, 20, 50, and 75 per cent of alcohol respectively 

 The relation as we shall see, does not hold good for the solution 

 containing 75 per cent alcohol and so, in computing the value 

 of A for these solutions, we must omit the determination for the 

 solution containing 75 per cent alcohol. The average difference 

 in logio Xy for 10 per cent increase in y is computed by adding 



