PASSAGE INTO SOLUTION 



283 



have had occasion to comment upon the fact (Cf. Chap. V) 

 that dry casein will not pass into solution in dilute acids, although 

 wet, flocculent, freshly precipitated casein will do so; never- 

 theless, acid is taken up from the solution and bound by the 

 casein (103). It appears probable, as I indicated in Chap. V, 

 that in this case soluble casein salts are formed but that they 

 are prevented, by the grossness of their molecules, from passing 

 out through the pores of the casein particles into the body of 

 the solvent. 



The influence of neutral salts upon the rate of solution of 

 casein by dilute sodium hydroxide has been investigated by 

 Robertson and Miyake (89) who find that even in the presence 

 of high concentrations of these salts the relationship between 

 the time and the amount of casein dissolved is expressed by the 

 relation x = Kt"^. The presence of the salts retards the solu- 

 tion of the casein, however, the retardation due to alkaline 

 earth chlorides being about one hundred times as great as that 

 which is brought about by chlorides of the alkalies. The degree 

 of retardation increases with increase of the concentration of 

 salt employed. 



The amount of casein which is dissolved, in a given period of 

 time, by a solution of KOH is, within the limits of accuracy of 

 the determinations, directly proportional to the concentration of 

 the KOH solution. This is very clearly shown in Table IV, in 

 which r denotes the ratio of the number of grams of casein dis- 

 solved to the number of equivalent gram molecules (multiplied 

 by 100) of KOH present in 100 cc. of solvent employed. It will 



TABLE IV 



* Average of two determinations at 26.5 degrees and 18 to 20 degrees, respectively. 



