SOLUBILITY OF VEGETABLE PROTEINS 31 



B. Solubility in Saline Solutions. 



As already stated, a large proportion of the different seed proteins 

 are soluble in neutral saline solutions from which they are precipitated 

 by removing the salt by dialysis or by abundant dilution. Proteins 

 having such solubility have been found in small or large proportion in 

 all the seeds thus far examined, and in a majority of them they con- 

 stitute the greater part of the reserve protein. The concentration of 

 the neutral salt solution required to dissolve these globulins varies very 

 widely, not only with the nature of the salt but also with that of the 

 protein. Some of the seed globulins are but slightly soluble at the 

 room temperature in sodium chloride solutions when these contain less 

 than 2 per cent, of this salt, while others are readily soluble in solutions 

 containing only a few tenths of I per cent. The degree of solubility 

 of many seed globulins depends much on the temperature of the solu- 

 tion and increases rapidly at about 30. 



The solubility of these proteins in solutions of various salts has 

 been studied by Osborne and Harris (357) with edestin. As this pro- 

 tein is entirely insoluble in water, the solvent effects of the addition of 

 various quantities of different salts- were determined in the following 

 manner. Portions of 2 grammes each of pure crystallised edestin were 

 suspended in sufficient water to make a final volume of 20 c.c. with 

 the different quantities of molar solutions of the several salts which 

 were afterwards added, the edestin being in each case in excess of the 

 amount dissolved. After agitating for some time, the solutions were 

 filtered, nitrogen was determined in 10 c.c. of each, and the amount of 

 edestin dissolved was calculated from the nitrogen in solution. It was 

 thus found that the amount of dissolved edestin was closely propor- 

 tional to the concentration of the salt solution. Its solubility in solu- 

 tions of sodium, potassium or caesium chlorides was nearly the same. 

 In solutions of magnesium, calcium, strontium or barium chloride its 

 solubility was twice as great as it was in the solutions of the chlorides 

 of the monovalent bases, with the exception of lithium chloride, in 

 solutions of which it did not dissolve as abundantly as in those of the 

 chlorides of the other monovalent bases. The sulphates of potassium, 

 sodium, lithium and magnesium had a solvent power corresponding 

 closely with that of the chlorides of the divalent bases. 



Bromides and iodides did not behave like chlorides, for sodium and 

 potassium iodides had a solvent power twice as great as that of the 

 corresponding chlorides, agreeing in this respect with the chlorides of 

 the divalent bases. The bromides were less energetic solvents than the 



