APPLICATIONS OF THE PHASE-RULE 123 



CI CI 



-COH++ +^N- -I- NaNOa = -CONa = N- + HNO3 

 I I 



H H 



OH ' CI 



-CONa++ + ^N- + KCl = -CONa = N- + H2O. 

 I I 



H K 



The symmetry of the action of the salts upon the acid and 

 alkali protein compounds would appear, however, to indicate a 

 greater similarity in the structure of the compounds formed 

 than that which is suggested by these formulae. 



5. Applications of the Phase-rule to Protein-salt-water Sys- 

 tems. — In addition to the above investigations attempts have 

 been made to interpret the behavior of the proteins in the pres- 

 ence of salts, in the light of the phase-rule, starting from the 

 view developed by Spiro (74) (10) that the coagulation of pro- 

 teins by salts might be regarded as a separation of the system 

 into two phases, a solid phase rich in protein, or a protein-salt 

 compound, and poor in salt and water, and a liquid phase poor 

 in protein, rich in salt and water. 



The phase-rule, as developed by Willard Gibbs (19), van't 

 Hoff and Roozeboom may be enunciated as follows: A system of 

 r coexistent phases containing n independently variable compo- 

 nents is capable of n -\- 2 — r variations in the temperature, 

 total pressure of the system or concentration of the components 

 of its phases. A "phase" is a portion of the system separated 

 from the rest by a definite surface, the "independently variable 

 components" are the least number of different substances with 

 which it is possible to represent, in a chemical equation, the 

 composition of each phase in the equilibrium (14). Only equi- 

 libria are contemplated in the derivation of the phase-rule, con- 

 sequently it is not applicable to systems which by reason of 

 hysteresis or limited reaction-velocity * are in a condition of 

 incomplete equilibrium. A discussion of the theoretical basis of 



* Unless the reaction-velocity in question is so small as to be negligible in 

 comparison with the velocity with which the equilibrium under examination 

 is attained; for example, the hydrolysis of protein by water in the system 

 protein -salt-water. 



