40 



THE VEGETABLE PROTEINS 



the usual methods, has the same properties as the edestan which results 

 from the action of acids on the unchanged edestin, for if preparations of 

 edestin, made by the commonly employed methods, are treated with 

 water and the solution of the soluble part is precipitated by the addi- 

 tion of a little sodium chloride, the precipitate produced, when treated 

 with a larger proportion of sodium chloride, leaves an insoluble residue 

 which in all respects is the same as that obtained by the action of acids 

 on the unchanged edestin. 



The ultimate composition of edestan differs little, if at all, from that 

 of edestin, as is shown by the following analyses of three samples of 

 edestan made under somewhat different conditions and also by an 

 analysis of a sample of unchanged edestin. Preparation I. was made 

 by suspending 10 grammes of crystallised edestin chloride in water 

 and gradually adding 30 c.c. of a decinormal solution of hydrochloric 

 acid. After the clear solution which resulted had stood at 20 for 

 about two hours it was made neutral to phenolphthalein with 38 c.c. 

 of decinormal potassium hydrate solution, and the precipitate produced 

 was washed with I o per cent, sodium chloride solution until all of the 

 unchanged edestin was removed, and then with water until free from 

 chlorine. After dehydrating with absolute alcohol, the preparation 

 was dried at 110. Preparation II. was made in the same way, 

 except the acid solution was kept at a temperature below 10 for 

 about twenty hours, when 50 c.c. of decinormal potassium hydrate 

 solution was added. Although this excess of alkali was more than 

 sufficient to dissolve the entire quantity of the precipitate produced by 

 neutralisation, had this been unchanged edestin, nevertheless very little 

 protein matter was dissolved by it. Preparation III. represents the 

 insoluble edestan which was obtained directly from a preparation of 

 edestin and is the insoluble substance which is commonly found in 

 such preparations. 



It is to be noticed that the amount of nitrogen found in the three 

 samples of edestan is very constant and slightly less than that found 



