PROTEINS 147 



In the organism proteins only occur accompanied by electrolytes 

 which greatly modify their properties. On this account we shall try 

 to get an idea of albumin unassociated with electrolytes in order to un- 

 derstand the influence of the addition of electrolytes. 



Electrolyte-Free Albumin. 1 



WOLFGANG PAULI obtained an albumin free from electrolytes by 

 dialysing ox serum in closed vessels for eight weeks. After standing 

 undisturbed for several weeks, the serum was filtered and was found 

 to furnish a stable crystal-clear fluid. Boiling and the addition of 

 alcohol completely coagulated the solution. Such albumin is am- 

 photeric with a weakly electronegative charge; so that it consists 

 chiefly of neutral and very slightly ionized particles 2 which migrate 

 to both electrodes in an electric field (L. MiCHAELis* 3 ) . According 

 to L. MICHAELIS and P. RONA, the isoelectric point for serum al- 

 bumin, at which there is the greatest tendency to precipitation, occurs 

 with an H-ion concentration of 2.10~ 5 ; for boiled, denatured serum 

 albumin when the H-ion concentration is 4.10~ 6 . It increases the 

 internal friction of water considerably. If the friction coefficient 

 of water is represented by 1000, a 1 per cent amphoteric albumin 

 solution at the same temperature will be 1068. An equimolecular 

 1 per cent salt solution causes no demonstrable change in the coeffi- 

 cient of friction of water. 



Solubility in Albumin Sols. 



We shall see in the following pages that albumin usually has a 

 powerful influence on the solubility of substances. It is a remark- 

 able fact that the solubility of carbonic acid is the same in an 

 albumin sol as it is in water (A. FINDLAY*). This is all the more re- 

 markable since starches and gelatins, in contradistinction to albumin, 

 are very active in affecting the solubility of carbonic acid. This is 

 physiologically important, since serum consequently plays no part 



1 The colloid-chemical study of proteins was inaugurated by F. HOFMEISTER 

 and his pupils; in recent times they have been studied chiefly by Wo. PAULI 

 and his co-workers in numerous experimental investigations. We wish espe- 

 cially to call attention to Wo. PAULI and H. HANDOVSKY, HOFMEISTER'S Beitr. z. 

 Chem. Physiol. u. Pathol., 11, 415-448; Biochem. Zeitschr., 18, pp. 340-371. Loc. 

 cit., 24, 239-262. Further references in the text book of H. FREUNDLICH and Wo. 

 OSTWALD as well as in H. HANDOVSKY, Koll.-Zeitschr., 4 and 5 (1910). 



2 Since an absolutely ash-free albumin cannot be prepared by dialysis as 

 shown by the investigations of PAULI and the unpublished experiments of H. 

 BECHHOLD and J. ZIEGLER, it is apparent that the question of the electric charge 

 of pure albumin is not yet definitely determined. 



