X PREFACE 



second law of heat to protein systems has, in some quarters,* been 

 questioned. In considering the electrochemical behavior of the 

 proteins I have assumed the applicability of Arrhenius' hypothesis 

 of electrolytic dissociation, of Kolrausch's law of the independent 

 motion of ions, of the Nernst theory of concentration-cells, and 

 further, although this has of recent years been very strongly 

 questioned,! the applicability of the Guldberg and Waage mass- 

 law to reactions between ions. I believe that the utility of these 

 hypotheses justifies us in applying them until still more useful 

 hypotheses shall have been elaborated to amplify or replace them. 



A previous edition of this work appeared, in German, six years 

 ago.J Since that time our knowledge of the physico-chemical 

 behavior of the proteins has very considerably expanded and in- 

 creased in exactitude. Among the particularly important in- 

 vestigations which have appeared during this period may be men- 

 tioned the invention by Van Slyke of an accurate and simple 

 method of determining free amino-groups (Cf. Chapter I), the 

 work of Pauli upon the combining-capacity of deaminized pro- 

 teins (Cf. Chapters I, VIII and IX), the work of Schmidt and of 

 af Ugglas upon compound proteins (Cf. Chapter VII), the work 

 of Procter upon the swelling of protein jellies (Cf. Chapter XII), 

 the work of Reichert and Brown upon the crystallography of 

 haemoglobin (Cf. Chapter XII) and that of Dabrovsky upon the 

 molecular volumes of proteins dissolved in water and in solutions 

 of coagulating salts (Cf. Chapter XIII). The present edition 

 has been almost entirely rewritten and the literature has been 

 brought down to the middle of 1917. 



In conclusion I wish to express my very great indebtedness to my 

 wife, for her assistance in preparing the manuscript for the press, 

 to Dr. Hardolph Wasteneys for his assistance in proof-reading, 

 and to Dr. C. L. A. Schmidt for his assistance in proof-reading 

 and in the verification of many references and formulas. 



T. BRAILSFORD ROBERTSON. 



BERKELEY, CALIFORNIA, 

 Nov. 1, 1917. 



* von Schroeder, P., Zeit. f. physik. Chem., 45 (1903), p. 75. Dietz, W., 

 Zeit. f. physiol. Chem., 52 (1907), p. 279. Cf., however, Chapter XVII. 



t Cf. for example, W. Sutherland, Phil. Mag. Series 6, 14 (1907), p. 1. 



t " Die physikalische Chemie der Proteine," Dresden, 1912. Theodor Stein- 

 kopff. 



