284 



CHEMISTRY OF THE PROTEIDS 



CHAP. 





Other interesting points discovered by Posternak were, that the 

 same acid radical produces in different salts different effects : 



HC1 NH 4 C1 KC1 NaCl 



0-388 0-385 0'380 0'325, 



and that the same acid which in dilute strengths favours solution 

 causes precipitation when it is concentrated. This fact is attributed 

 to a change in the electrical conductivity, thus : 



Strength of HC1. 



1 :1000 



1,415 : 1000 



dissociated molcules 



= 19, while 



Molecular concentration. 

 0-0273 

 0-388 



Conductivity. 



0-95 

 0-86 



In the first case the quotient 



non-dissociated molecules 

 in the second case it is 6. 



Ordinary abumins being electro-negative are coagulated, according 

 to Hofmeister and Pauli, see p. 288, by kations in the following 

 order : 



Li>Na>K>NH 4 >Mg, 



while the electro-negative anions tend to prevent coagulation in this 

 order : 



Fl > S0 4 > P 2 5 > citrate > acetate > 01 > NO 3 > Br > I > CNS. 



Posternak has now observed the very interesting fact that if the 

 reserve material of Picea dissolved in 1 : 1000 HOI be taken, that 

 the order of the above salts is inverted, the electro-positive albumin is 

 now precipitated by anions in this order : 



CNS>I>Br>N0 3 >Cl>acetate, 



while the coagulation-inhibiting kations follow in this order : 

 Mg>NH 4 >K>Na. 



This phenomenon is interesting in connection with Hardy's experiment 

 on heat-coagulated albumin, which may behave either as a kation or 

 as an anion (see p. 278). Pauli has also drawn attention to the fact 



