62 COLLOID CHEMISTRY OF THE PROTEINS 



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The natural explanation of these relations is that with low 

 content of albumin at constant acidity the behaviour of the 

 H- and Cl' ions approaches that which obtains in presence of 

 excess of acid, whereas when much albumin is present the 

 behaviour is akin to that of complete combination of the acid. 

 When the same series of determinations is made at higher con- 

 centrations of acid, the divergence of the curves is displaced in 

 the direction of the higher concentration of albumin (Fig. 12). 

 At the same time these investigations lead to the observation 

 that the measurements of Bugarsky and Liebermann give too 

 high a value for the free H- ions, and consequently the figures 



for combined acid are 

 too low (compare Fig. 12 

 and Fig. 9). 



The maximum ionisa- 

 tion of albumin chloride 

 implies a maximum of 

 positively charged albu- 

 min particles, and an 

 investigation of the 

 migration of acid 

 albumin by Pauli and 

 Samec * goes to prove 

 this. With constant 

 difference of potential 

 the quantity of albumin moving towards the cathode falls off 

 again when the concentration of acid rises above 0-05 N. 



Previous to the more recent electrometric measurements given 

 above, the behaviour of acid albumin on ionisation and the 

 existence of a maximum value for the ionisation were deduced 

 from observations on the viscosity of such mixtures. The work 

 of Pauli and Handovsky f showed that when hydrochloric acid 

 is added to albumin (e.g., a i percent, serum albumin solution), 

 a considerable rise in viscosity occurs. A maximum value is 

 obtained between 0-017 N and 0-02 N acidity, further addition 

 of acid causing a decrease in viscosity (Table 21, Fig. 13). 



* Not yet published. 



j Biochem. Zeitsch., 1909, 18, 340. 



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FIG. 12. Combination with variable protein 

 concentration. 



