PROCEEDINGS OF SECTION D. 501 



nection it occurred to me that many of the difficulties encountered in 

 applying physico-chemical laws to protein systems might possibly be 

 attributed to the insufficient consideration of the amphoteric nature of 

 proteins, and of the manner in which the ordinary conditions of chemical 

 equilibrium are thereby modified. That the ordinary laws of chemical 

 statics, as applied to dilute solution of non-amphoteric electrolytes are 

 greatly modified in amphoteric systems, has been pointed out by Walker 

 (SO), who Avorked out the equations for the equilibrium of a non- 

 associating ampholyte in the absence of other electrolytes. It is obvious, 

 however, that the problem we have to consider is even more complex 

 than that discussed by Walker. In the first place we frequently wish to 

 consider the reactions of proteins towards non-amphoteric electrolytes, 

 and so we have to include these in the system. In the second place 

 "Walker's equations do not take into consideration the possibility of the 

 formation of association compounds or of polmeric modifications of the 

 amphotetic electrolyte, analogous to the polypeptids to which I have 

 referred, such as undoubtedly occur in the case of proteins. The marked 

 influence of temperature upon the state of aggregation of proteins and 

 the precipitate on neutralising a solution of acid — or alkali — albumin, 

 to mention two well-known instances, point to the formation of large 

 molecule-complexes, or, as Hardy (70) has called them, " pseudoions " ; 

 nor can we place any definite limit to the number of such different 

 complexes which may be in equilibrium in a solution of protein. Indeed, 

 we must regard the coagulation of proteins rather as a shifting of this 

 equilibrium in the direction of higher complexes than as a sudden 

 chemical or physical change unpreceded, even in minute concentrations, 

 by similar molecular aggregations at a different temperature, or at a 

 difi^erent concentration of the coagulating agent. Similarly we must 

 regard the solution and swelling of proteins as a shifting of the 

 equilibrium in the direction of lower complexes. Even in the simplest 

 possible instance of an ampholyte, namely, water, Arrhenius (81), 

 and, more recently, Sutherland (82), have pointed out that such 

 polymeric modifications must at all times exist in equilibrium with 

 each other, the point of equilibrium being shifted by alterations in 

 temperature. 



I accordingly carried out a mathematical investigation on the condi- 

 tions of equilibrium of an associating amphoteric electrolyte in the 

 presence of any number of non-amphoteric electrolytes (68). Before 

 briefly outlining the results of this investigation, which most intimately 

 bear upon the properties of the ion-proteids, I must preface an accovmt 

 of the terminology used, as it will serve also to illustrate some of the 

 most important properties of an ampholyte system. 



An uncombined ampholyte can be represented in a general way by 

 the symbol HXOH where X is any radicle. Ampholytes which may be 

 represented, as regards their dissociation, by the symbols H+ + XOH" 

 and HX+ -f- 0H~ are designated acid and basic ampholates respectively, 

 to distinguish them from their salts. 



The simplest ampholato in a given system, represented by HXOH^ 

 is designated the ampholate of the first order ; those represented by 



HXXOH , HXXX OH being designated ampholates of the 



second nth orders. The compounds of an acid ampholate with a 



