122 CHEMICAL STATICS 



this coagulum, addition of water then results in the precipitation 

 of copper albuminate. 



The concentration-range throughout which the salt acts as 

 solvent may be evanescent, as it is in the case of silver nitrate 

 acting upon egg-albumin (Pauli). 



It was already shown in 1833 by Rose (68) that haemoglobin 

 is coagulated by concentrated mercuric chloride, but may be 

 redlssolved by dilution, to be precipitated on further dilution. 



The very important observation has been made by Pauli (56) 

 that absolutely electrolyte free egg-albumin is not ionic (i.e., 

 does not drift in an electric field) and that under these conditions 

 it is not precipitable by heavy metals. It is, however, coagulated 

 by highly concentrated salts.* 



Accordmg to Pauli and Handovsky (57) (60) the number of 

 ionized protein particles in a solution of ionic protein is dimin- 

 ished by the addition of salts; at the same time the viscosity of 

 the solution diminishes and the coagulability of the protein by 

 the usual coagulating agents is increased. When salts are added 

 to a solution of electropositive protein (i.e., protein combined 

 with acid) an increase in the acidity of the solution results (24). 

 They beheve that acid-protein reacts with salts as follows: 



/ ^Cl / ^Cl 



R\ + NaNOa = R< + HNO3, 



^COOH ^COONa 



while alkali-protein reacts as follows: 



/ ^OH / ^Cl 



R\ e + KCl = R\ + H2O. 



^COONa * ^COONa 



On the basis of the more probable view of the electrolytic 

 dissociation of proteins outlined in Chap. I, this hypothesis 

 would be represented by the following schematic formulae: 



* Egg-albumin is nearly equally basic and acid. It is probable that the 

 proteins which are either predominantly acid or basic may still, in some 

 measure, be electrolytically dissociated when uncombined with bases or acids. 



