PREFACE ix 



of the proteins, but upon that of the colloids in general, have re- 

 sulted in the development of two rather sharply differentiated 

 schools of opinion. The one school endeavors, so far as technical 

 difficulties permit, to directly apply, with modifications suggested 

 by the properties and structure of the particular colloid under 

 investigation, the known laws of what may be termed "molec- 

 ular" physical chemistry to protein and other colloidal systems, 

 while the other school hesitates to do so. The essential question 

 at issue between these two schools, in so far as the proteins are 

 concerned, is, I think, simply this: Are we justified in assuming 

 that the rule of Avogadro is applicable to protein solutions or are 

 we not? In other words, are protein solutions molecularly dis- 

 persed systems or are they, rather, suspensions or emulsions? 

 The latter of the two schools to which I have referred avers from 

 a priori considerations, implicitly or explicitly, that Avogadro's 

 rule may not be applied to protein solutions, or, at least, that its 

 validity for these solutions should be established before we venture 

 to apply it. The former school prefers to assume that Avogadro's 

 rule does apply to these systems until actual inapplicability 

 demonstrates that it does not. Now the " proof " of the applica- 

 bility of Avogadro's rule to systems which are admittedly molec- 

 ularly dispersed has never consisted in anything but the appli- 

 cability, to these systems, of laws and deductions founded upon 

 Avogadro's rule. The procedure of the former school would 

 appear, therefore, to be sound and well justified by scientific 

 precedent. Following this procedure we will be enabled to cor- 

 relate and interpret the phenomena which are exhibited by such 

 protein systems as may chance to be molecularly dispersed, while, 

 on the other hand, we shall be enabled to accurately delimit the 

 conditions under which molecularly dispersed protein systems 

 exist and those under which they do not. 



In this work I have endeavored to interpret the physico-chemi- 

 cal behavior of the proteins in the light of the laws of Boyle and of 

 Gay-Lussac, as they have been applied to solutions by van't Hoff, 

 and of the Guldberg and Waage mass-law which, as Larmor has 

 shown, is a direct consequence of Avogadro's rule and Boyle's 

 law.* I have also assumed the validity, in protein systems, of 

 the first and second laws of heat, albeit the applicability of the 



* Larmor, J., Phil. Trans. Roy. Soc. London, 190 A (1887), p. 276. T. Brails- 

 ford Robertson, Journ. Physical Chem., 10 (1906), p. 521. 



