H. GUTFREUND 



G. S. Adair studied the influence of high concentrations of sodium 

 chloride upon the osmotic coefficient of concentrated (20 per cent) 

 haemoglobin solutions 4 ; he showed that it was considerably increased. 

 If only interaction phenomena or the entropy of the solution are 

 responsible for the increase in the osmotic coefficient, then P/C should 

 still extrapolate to 3-5 for C = 0. Figure \c shows the plot of the 

 data from Tables III and IV obtained from measurements on solutions 

 of horse and human haemoglobin in 0-2M phosphate + 1M sodium 

 chloride. The points on this graph corresponding to protein con- 



centrations of 5 per cent and above could be extrapolated to -=, 



3-5 



for C = and the slope of this line is steeper than that obtained for 

 either of the two haemoglobins in phosphate solution. None of the 

 points below protein concentrations of 5 per cent would fall on this 

 line of extrapolation and it must therefore be assumed that some other 

 effect is taking place which increases the osmotic coefficient for dilute 

 solutions, and this cannot be due to any of the three causes given 

 above. The only possible explanation for large osmotic coefficients in 

 the more dilute solutions can be found in progressive dissociation of 

 horse and human haemoglobin molecules on dilution in 1M sodium 

 chloride solutions. 



A further series of experiments was carried out on horse haemo- 

 globin in 2M sodium chloride. The data recorded in Table V are 

 plotted in Figure Id. Again the data obtained for the more con- 

 centrated haemoglobin solutions could be extrapolated to P/C = 3-5, 

 giving an even steeper slope than that obtained from data on solutions 

 in 1M sodium chloride. In the more dilute haemoglobin solutions 



Table V 



Table VI 



202 



