152 COLLOIDS IN BIOLOGY AND MEDICINE 



Acid Albumin. 



There is a marked change in the properties of amphoteric albu- 

 min when acid is added to it. It migrates to the cathode as though 

 it were the basic portion of a salt; it loses its coagulability by heat 

 and alcohol, its internal friction is greatly increased and its surface 

 tension diminished. If an excess of acid is added, coagulability by 

 acids and alcohol is restored and its viscosity diminishes. 



SJOQUIST* was of the opinion that albumin formed with acids 

 strongly hydrated (swollen) ionized salts. This assumption was con- 

 firmed by the researches of ST. BUGARSZKY and L. LIEBERMANN* and 

 of K. SPIRO and PEMSEL.* It was finally established by MAUABE 

 and J. MATUTA by extremely accurate measurements on the ioniza- 

 tion constants of acid albumin. W. PAULI and M. HIRSCHFELD then 

 established that albumin was polybasic, i.e., behaved like a tri- or 

 tetra-amino acid, and that the salts were subject to the normal hydro- 

 lytic dissociation, characteristic of weak bases. S. ODEN and W. 

 PAULI conclude from the rise in migration velocity with increasing 

 fixation of acid that polyvalent protein ions are formed. 1 



In a solution containing about 1 per cent albumin, the maximum 

 internal friction is reached at 0.016 normal HC1, and falls with 

 greater concentrations of acid. Such a maximum is also found with 

 other acids (oxalic acid, sulphuric acid), while with others (acetic 

 acid, citric acid) a continual rise in internal friction accompanies the 

 concentration of the acid. 



Precipitability by alcohol runs parallel with the increase or decrease 

 in the internal friction (K. SCHORR). 



When amphoteric albumin has been made incoagulable by acids, 

 the addition of neutral salts restores the coagulability by heat and 

 alcohol. All the salts investigated (NaSO 4 , NaNO 3 , Na 3 P0 4 , Na- 

 acetate, Na-formate, etc.) depress the internal friction. In this re- 

 spect, the cations are of lesser importance, the anions being decisive 

 in the following order: 



Cl < NO 3 < SON < S0 4 < C 2 H 3 2 . 



Nonelectrolytes (cane sugar, urea) have, on the contrary, little 

 influence in this respect. 



Caffein and its salts are an exception, as they increase the internal 

 friction of acid albumin (H. HANDOVSKY* 2 ). 



An excess of acid alone or the addition of neutral salt to an amount 

 of acid which is insufficient to cause precipitation causes at first a 



1 See also W. E. Ringer, Acid Fixation by Albumin and Viscosity, Van 

 Bemmelen-Festschrift (Helder i.H.u. Dresden, 1910), 243-60- 



