SOLUBILITY OF VEGETABLE PROTEINS 33 



Neutral edestin and " edestin monochloride " have the same solubility, 

 but are more soluble than " edestin dichloride ". 



The results obtained with sodium sulphate, which in sufficient con- 

 centration precipitates edestin, are of interest, for, while solutions of 

 this salt up to a certain degree of concentration dissolve edestin in the 

 same proportion as do solutions of a corresponding molecular concen- 

 tration of potassium, lithium or magnesium sulphates, the solvent power 

 of more concentrated solutions diminishes with increasing concentration, 

 until by a molar solution of this salt practically no edestin is dissolved. 

 The curve showing the solubility of edestin in solutions of different 

 concentrations of potassium sulphate is the same as that of correspond- 

 ing solutions of sodium sulphate up to the point of saturation of the 

 solution with potassium sulphate. 



The solubility of potassium sulphate is so small, however, that molar 

 solutions cannot be made, but if sodium sulphate is added to the satu- 

 rated solution of potassium sulphate in such quantity that the solution 

 contains as many molecules of the two sulphates as does the corre- 

 sponding solution of sodium sulphate alone, the solubility of edestin in 

 the solution of these mixed sulphates is the same as that in a solution 

 containing only sodium sulphate. 



C. Solubility in Acids and Alkalies. 



As the solubility of the isolated proteins in acids and alkalies has 

 already been discussed in dealing with their basic and acid properties, 

 and will be further considered in other aspects in connection with the 

 question of denaturing and also in describing the properties of the 

 group of glutelins, it need not be dealt with here further than to men- 

 tion the fact that zein, the alcohol-soluble protein of maize, can be dis- 

 solved in boiling glacial acetic acid without undergoing apparent change 

 (308), for on pouring the acetic acid solution into water and treating the 

 resulting precipitate atoncewfa 70 per cent, alcohol, it dissolves in the 

 same manner as does zein similarly precipitated from an alcoholic solu- 

 tion \cf. also Kjeldahl (190)]. 



D. Solubility in Alcohol. 



The seeds of cereals, with the exception of rice, contain much pro- 

 tein soluble in alcohol of from 70 to 90 per cent. In this respect these 

 proteins show a marked contrast in their solubility to all the other pro- 

 teins of animal or vegetable origin. They dissolve in alcohol of suffi- 

 cient strength in all proportions, so that their solutions, under proper 

 conditions, can be concentrated to thick syrups, from which the protein 



3 



