44 THE GENERAI^ CHARACTERS OF THE PROTEINS 



Iog 10 cl were plotted as ordinates and abscissae, and a curve drawn. 

 C H 



By means of this curve the value -~ l could be ascertained by each 



experimentally determined value E - E o . 



The following were some of the results obtained : 



From the above table it is clear that the egg-protein combines 

 both with acid and alkali, and it must be conceded that Bugarsky 

 and Liebermann have by this method clearly demonstrated the am- 

 photeric character. The addition of protein to sodium chloride in 

 another form of galvanic cell produced no change in electro-motive 

 force ; the combination took place only with bases and acids. 



A. III. Depression of Freezing-Point Methods. 



Bugarsky and Liebermann also employed this method. They 

 determined the depression of the freezing point caused by the addition 

 of definite quantities of protein to pure water (S). They then added 

 the same quantities to 0*05 N hydrochloric acid, sodium hydroxide 

 and sodium chloride solutions, and determined the depression in the 

 freezing points of these solutions. If D be the depression of the 

 freezing point of these solutions before the addition of protein, and 

 A the observed depression after addition of the protein, it was found 

 in the case of the acid and the base that A was less than D + S. In 

 the case of the salt A = approx. D + 8. This indicated the diminu- 

 tion of the number of molecules in solution, due to the combination 

 of the protein with acids or bases. No combination took place with 

 the salt. These experiments confirm the results obtained by the 

 electric potential method. 



A. IV. Hydrolysis of Cane-Sugar and Esters by Acids and 

 Bases in Presence of Proteins. 



This method was originally employed by Hoffmann for deter- 

 mining the free hydrochloric acid in gastric contents. It has also 

 been employed by O. Cohnheim for estimating the combining powers 

 of various products of protein digestion with hydrochloric acid, and 

 by Hardy for determining the amount of hydrolysis in the hydro- 

 chloric acid compounds of serum-globulin. More recently still it 

 has been applied by B. Moore for investigation of gastric contents 



