LATER INVESTIGATIONS 119 



run parallel with the degree to which they are "adsorbed" by 

 finely pulverized charcoal. 



Biltz (5) also considers that the precipitation of colloids by 

 electrolytes and by other colloids is due to the formation of 

 "adsorption compounds." 



4. Later Investigations on the Significance of the State of 

 Hydration of the Proteins in Relation to their Coagulation by 

 Electrolytes. — Continuing his investigations, cited above, on the 

 coagulating action of pairs of salts on egg-white, Pauli (53) found 

 that a number of salts which will not coagulate egg-white by 

 themselves will increase the coagulating power of other salts 

 when mixed with them, while others markedly diminish the 

 coagulating power of salts which, in their absence, readily coagu- 

 late egg-albumin. Moreover certain salts, although very soluble, 

 do not in any concentration cause coagulation of egg-white. 

 The possibility suggested itself that the coagulating action of 

 salts might depend upon two antagonistic factors, respectively 

 attributable to the cations and the anions of the salts. In con- 

 firmation of this view it was found that the NH4 ion, when com- 

 bined with SO4 will coagulate egg-albumin, although when com- 

 bined with acetanion it will not. Acetanion coagulates when 

 combined with sodium, but not when combined with ammonium. 

 Pursuing this line of reasoning and [investigation Pauli concluded 

 that if the coagulating powers of a series of cations be indicated 

 by /> f, /". • • • and the opposite (solvent) powers of a series 

 of anions by h, Ji', h", . . . , then in a mixture of electrolytes the 

 following possibilities exist: 



the mixture being such as to coagulate, leave unaffected or in- 

 hibit the coagulation of the albumin. Pauli found that in egg- 

 white (in which the protein is electronegative) the cations of 

 added electrolytes are the active agents in inducing coagulation, 

 while the anions inhibit coagulation. In the following table of 

 Pauli's the cations are arranged in ascending order of precipi- 

 tating-power from left to right, while the anions are arranged 

 vertically, the weakest inhibitor coming first and the strongest 

 last. A (-[-) indicates that the salt which results from the union 

 of the cation and anion causes coagulation of egg-albumin; while 

 a ( — ) indicates that it does not. 



