Osmotic Pressure of Haemoglobin 



the results are very similar in the two cases, though the dissociation 

 effect may be slightly more marked in 2M sodium chloride. 



Three measurements of the osmotic pressure of horse haemoglobin 

 in 2M lithium chloride are recorded in Table VI. Some preliminary 

 experiments with this electrolyte were undertaken on account of its 

 large activity coefficient as compared with that of sodium chloride in 

 two molar solutions. The results so far obtained, though quite in- 

 complete, indicate even greater interaction effects at high haemoglobin 

 concentrations and also greater dissociation effects in more dilute 

 solutions of horse haemoglobin. It would be premature to draw any 

 conclusions from this, but more detailed studies on haemoglobin in 

 lithium chloride solutions of varied concentrations as well as in con- 

 centrated solutions of several strong electrolytes of varied activity 

 coefficients may yield valuable results. 



It is evident from the above results that differences of osmotic 

 pressures of proteins in solutions of varied composition, must be 

 interpreted with great caution. A complete set of data comprising 

 measurements over a wide range of protein concentrations in each 

 solvent is essential even if there is no danger of interference through 

 partial pressure of excess diffusible electrolytes. The results and 

 discussion given here form necessarily only a preliminary report. 

 Much more detailed studies on these lines should enable one to carry 

 out a thermodynamic analysis of intermolecular forces (interaction 

 energies) and of the intramolecular forces holding the subunits of the 

 haemoglobin molecules together. The former could be co-related with 

 the change of average intermolecular distance on change of protein 

 concentration and thus afford an interesting study of long range forces 

 in solutions of varied composition. 



Received September 1948 



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