GENERAL CHEMICAL CHARACTERS OF PROTEINS 49 



An edestin preparation, almost neutral to phenol phthalein, was 

 obtained by allowing the crystals to separate from a sodium chloride 

 solution containing sufficient sodium hydroxide solution to neutralise 

 the acid ; the amount necessary was determined by the titration of 

 a small aliquot part of the salt solution in the presence of phenol- 

 phthalein. 1 Portions, each of a gram, of this preparation were sus- 

 pended in 20 c.c. of liquid containing quantities of hydrochloric 



acid varying from 2-14 c.c., in a series of stoppered bottles. After 

 shaking for two hours, and allowing suspended matter to settle, 10 

 c.c. of clear liquid were decanted off, and the amount. of edestin in the 

 solution was estimated ; the acid contents of the solution and residue 

 were also determined, and the distribution of the acid between the dis- 

 solved and undissolved edestin thereby ascertained. Similar experi- 

 ments were carried out with other acids and also with alkalis. The 

 results obtained by this method of experiment may be briefly sum- 

 marised as follows : 



(1) The free base edestin, if suspended in water, requires some- 

 what more than that amount of acid to dissolve it than is necessary 

 to form a dihydrochloride, on the assumption that edestin has the 

 molecular weight 14,500. If the acid be added little by little to the 

 suspension practically no solution takes place till more than half 

 this quantity has been added; the insoluble monohydrochloride is 

 first formed. Somewhat more than the theoretical amount of acid 

 is necessary to produce complete solution owing to the formation of 

 a more basic hydrolysis product being formed, which is insoluble in 

 water (edestan). 



(2) The sulphates of edestin are less soluble than the chlorides, 

 and the existence of definite compounds has not been ascertained ; 

 ten times more sulphuric acid than hydrochloric acid is necessary to 

 dissolve a given quantity of edestin. Acetic acid, on the other hand, 

 dissolves nearly the theoretical amount (2 mol. acid : I mol. edestin), 

 as in this case little of the basic bye-product is formed. Phosphoric 

 acid acts as a monobasic acid, giving salts of the type B' . HoPO^ and 

 B" (H 2 P0 4 ) 2 . 



(3) In addition to acting as a base, edestin can also act as an 

 acid ; for solution of a given quantity of edestin one molecular equi- 

 valent of sodium or potassium hydroxide to one molecular equivalent 

 of edestin is necessary ; the solutions of the sodium and potassium 

 salts readily become turbid, owing apparently to hydrolysis. Rela- 

 tively larger quantities of the carbonates and of ammonium hydroxide 

 are necessary to bring about solution. 



With reference to edestin, the chief points of interest are that the 

 existence of definite salts both with acids and bases can be ascer- 

 tained ; with hydrochloric acid both a mono- and dihydrochloride 

 can be prepared, of which the latter only is soluble in water ; this 

 latter salt as well as the sodium and potassium edestin compounds 

 have a peculiarity, viz^ they are insoluble in the presence of minute 

 quantities of a neutral salt, although they dissolve in more con- 

 centrated solutions ; in such solutions they show the ordinary pro- 

 perty of globulins. 







1 Full details of the preparation of the free edestin are given in the original paper. 



