26 THE VEGETABLE PROTEINS 



phenolphthalein such protein salts show a less degree of acidity. 

 Edestin, even before it becomes neutral to phenolphthalein, when 

 dissolved in sodium chloride solution gives an alkaline reaction with 

 litmus which is undoubtedly caused by the edestin itself and not by 

 organic salts of the alkali, for such preparations yield less than 0x35 

 per cent, of ash which is neutral to litmus or phenolphthalein. To- 

 ward lacmoid edestin reacts distinctly alkaline, even when its solution 

 is noticeably acid toward litmus. It is therefore important, in deter- 

 mining the acidity of a protein solution, to use an indicator which 

 marks the reaction of the protein in question when that substance is 

 perfectly free from both bases and acids. 



As has been already stated, many preparations of edestin, which 

 are obtained by extracting hemp-seed with sodium chloride solution, 

 when washed with water dissolve to a greater or less extent. Deter- 

 minations of the proportion of acid combined with the water-soluble 

 edestin show its amount to be greater than that which is combined 

 with the part which does not dissolve, thus indicating the existence of 

 two different salts of edestin, one of which, soluble in water, contains 

 more combined acid than the other which is insoluble in water. This 

 difference in solubility is due to the proportion of combined acid, for, 

 when this is removed from either the soluble or the insoluble part, 

 no difference can be detected between the neutralised products which 

 result. 



If I gramme of pure neutral edestin is suspended in water and 

 a quantity of decinormal solution of hydrochloric acid which is just 

 sufficient to dissolve it all is added, it will be found that the amount 

 of acid required corresponds closely with the amount of acid contained 

 in I gramme of the water-soluble part of edestin preparations, and this 

 amount is just twice as great as the amount of acid combined with 

 I gramme of the insoluble part. This proportion, of two to one, 

 strongly suggests the existence of two different chlorides, one of 

 which contains twice as much acid as the other, although each yields 

 crystalline products of apparently the same form. The importance of 

 recognising the existence of such protein salts having different 

 solubility relations is manifest, for the evidence presented by differ- 

 ences in solubility would indicate that most of our edestin preparations 

 contained at least two different protein substances. Too much em- 

 phasis, therefore, cannot be laid on the existence of such protein salts ; 

 and the possibility of their occurrence should be kept constantly in 

 mind. 



That edestin forms no exception in its behaviour towards acids 



