132 CHEMICAL STATICS 



Na 

 I 



H 2 N.R.CONa=N.R.COOH + H 2 O 

 I 

 Cl 



H 

 I 



= H 2 N.R.CONa = N.R.COOH + NaOH. (iv) 

 I 

 Cl 



This decomposition will, naturally, take place more readily 

 in dilute acid than in alkaline solution; more concentrated acid 

 would, of course, abstract the sodium from the compound and 

 convert the whole of it into the acid-protein compound. In 

 either case the neutral compound which results may be insoluble. 

 When the active mass of water is diminished, however, for ex- 

 ample by the addition of a dehydrating agent or of a salt with 

 an affinity for water, this hydrolytic decomposition is prevented, 

 and the complex salt: 



Na 

 I 

 HsN.R.CONa = N.R.COO 



I Cl I 



may pass into solution. 



Further dehydration leads to the loss of H and OH by 

 terminal NH 2 and COOH groups, as depicted above, and the 

 formation of complex insoluble anhydrides. 



This hypothesis furnishes an explanation of the following facts: 



(i) That the addition of small concentrations of neutral salts 

 to a solution of acid-protein increases the acidity of the solution, 

 while the addition of salts to alkali-protein solutions does not 

 increase their alkalinity (vide equations i and ii). 



(ii) That acid-protein is precipitated by cations, alkali-protein 

 by anions (vide equation iii). 



(iii) Since the union between the salt and the protein is chemi- 

 cal in character, Schultzes' valency-rule would apply to the rate 

 of precipitation (Cf. section 3). 



(iv) The reaction (acidity or alkalinity) of the system being 

 maintained constant, the precipitation of the protein depends 

 only upon the active mass of water and not upon the active 



