66 THE VEGETABLE PROTEINS 



lysis is good evidence that at least two atoms of sulphur must be pre- 

 sent in their molecules. 



A study made by Osborne (316) of the sulphur content of a 

 number of thoroughly purified preparations of seed proteins has shown 

 that it is possible to determine the total sulphur of the protein with a 

 high degree of accuracy. The sulphur content of preparations of 

 edestin obtained from chloride solutions agreed closely with one 

 another and in all cases was less than that of preparations of edestin 

 obtained from sulphate solutions. The preparations from chloride solu- 

 tions consist chiefly of edestin chloride, while those from sulphate 

 solutions are chiefly edestin sulphate. The difference in the sulphur 

 content of these two salts of edestin was almost exactly equal to the 

 sulphur of the combined sulphuric acid as actually determined in the 

 products of neutralisation of the preparations in question. 



It has already been shown that preparations obtained from sodium 

 chloride solutions contain a very small amount of combined sulphuric 

 acid in addition to the combined hydrochloric acid, and in agreement 

 with this fact preparations of pure neutral edestin from which all the 

 combined acid had been carefully removed yielded a little less sulphur 

 than the preparations which still retained their combined acid. The 

 slight differences found between twenty-one preparations of edestin 

 (see p. 67), which amounted to only a few hundredths of a per cent, were 

 undoubtedly caused by differences in the relative proportions of com- 

 bined sulphuric and hydrochloric acids which these preparations con- 

 tained. Other similar determinations of the total sulphur in a number 

 of different proteins led to equally constant results, so there is no doubt 

 that these proteins contained definite quantities of sulphur. Deter- 

 minations, by Schulz' method, of the sulphur of different seed proteins, 

 converted into sulphide by boiling with caustic soda, yielded uniform 

 results which are given in the following table, together with similar 

 results obtained with some animal proteins which are introduced for 

 comparison. 



