24 THE VEGETABLE PROTEINS 



From these figures it is seen that most of the substance formed by 

 neutralising this preparation of edestin consisted of potassium salts 

 of mineral acids containing 73 per cent, of the potassium used for 

 neutralisation. It is thus evident that on precipitating edestin by 

 dialysis from a faintly acid solution in the presence of sodium chloride 

 and of the organic and inorganic salts extracted from the seed, this 

 protein combines with some of each of these acids according to the 

 concentration in which the several acid substances were present in the 

 solution at the time of precipitation, and that the crystalline precipitate 

 of edestin consists not of the free protein but of a mixture of its salts. 

 If such a precipitate of crude edestin, as was used for the experiment 

 just described, is recrystallised from a solution of pure sodium chloride, 

 it still contains a similar quantity of acid, but the inorganic salts which 

 result on neutralising contain a larger proportion of potassium chloride. 

 The composition of the salts obtained in such an experiment were as 

 follows : 



Per cent. 



Potassium carbonate yj 



Potassium sulphate 6*5 



Potassium chloride 73-9 



Sodium chloride 7-4 



Undetermined and loss 6-5 



These figures show that the proportion of potassium chloride is 

 greatly increased by thus recrystallising the edestin ; that the organic 

 acids from which the potassium carbonate originated, as well as the 

 sulphuric acid, are greatly diminished and that the potassium phos- 

 phate has entirely disappeared ; a result which would be expected if 

 the relative concentration of the different anions in the solution from 

 which the edestin was recrystallised is taken into consideration. 



Edestin extracted from the seed with ammonium sulphate instead 

 of sodium chloride yields, on neutralising, chiefly potassium sulphate 

 instead of chloride, as is shown by the following analysis of the salts 

 obtained in this way : 



Per cent. 



Potassium carbonate 18*98 



Potassium sulphate 77'34 



Potassium chloride 2'6i 



Undetermined and loss . . . 1*07 



lOO'OO 



In this case over 75 per cent, of the recovered potassium was in the 

 form of sulphate and less than 3 per cent, in that of chloride. 



If the neutralised edestin obtained in the last experiment, which 



