278 REPoRT OF THE CHEMIST OF THE 
THE HYDROLYSIS OF THE SODIUM Sais 
OP SCA Daa 
1. In determining the amount of alkali neutralized by casein, 
different indicators give cifferent results. Phenolphthalein has 
been in most common use in such work, giving higher results than 
other indicators. The object of the work presented was to de- 
termine the neutral point by means of conductivity measurements 
in comparison with the use of phenolphthalein and alkali. Our 
results indicate that the sodium salts of casein hydrolyze so readily 
that titration with alkali does not give the true equivalent weight 
of the proteid. An excess of casein, as of phosphoric acid, is re- 
quired to overcome the alkalinity of the hydrolizing normal salt. 
The point at which the alkalinity is overcome is indicated by the 
attainment of minimum conductivity and corresponds roughly with 
the point neutral to phenolphthalein. Because of the extreme 
weakness of its acid properties, markedly greater excess of casein 
is required to give an acid reaction with less delicate indicators. 
In determining the amount of alkali that is neutralized by casein, 
the results obtained by the use of different indicators do not agree. 
Thus, more alkali is required with litmus than with methyl orange 
and still more with phenolphthalein.t The amount of alkali which 
casein neutralizes, with the use of phenolphthalein as indicator, has 
been chosen somewhat arbitrarily as representing the true result. 
It was on the basis of results thus obtained that Laqueur and 
Sackur? made their determination of the equivalent weight of casein. 
The desirability of a method of measuring the neutral point in 
such cases, independently of indicators, is apparent. It was hoped 
that the determination of electrical conductivity would furnish this. 
It is well known that when an acid is added to a solution of a strong 
base, the conductivity of the solution decreases until the neutral 
— —-—___ —_—_. 
*Reprint of Part 11, Technical Bulletin No. 3. 
*So6ldner Landw. Vers.-Stat., 353351. 1888. 
Courant. Arch. Physiol. [Pfliiger], 50:109. 18o0T. < 
Laqueur. Beitr. Chem. Physiol. u. Path., 7:273. 1905. 
* Beitr. Chem. Physiol, u. Path., 3:197. 1903. 
