86 



HEMOGLOBIN 



The time factor looms almost as large in Adair's determinations as 

 in those of Hartridge and Roughton. The latter measure events which 

 take place in a fraction of 1/1000 of a second; Adair's osmometric 

 determinations each require a fraction of a year. The work is being 

 carried on in the Low Temperature Station at Cambridge, where 

 Sir Wm. Hardy kindly allows Adair to set up his osmometers. Such 

 work must be very slow, but already enough information has been 

 obtained to be of considerable interest. Adair will show you a model 

 in which the osmotic pressure in a 1 per cent, solution of haemoglobin 

 is represented vertically whilst the hydrogen-ion concentration and 

 the saline concentration of the solvent are as the horizontal co- 

 ordinates. Over a great area of this model the osmotic pressure 



10 20 30 



Concentration Hb 



Fig. 16. 



40% 



of the haemoglobin works out uniformly at 2-6 mm. of mercury, 

 even though the pH and the salt concentration vary (5), (6). 

 This figure is given if the solution is not more than 4 per cent, 

 haemoglobin or is not of less saline concentration than 0-01 molecular. 

 Where a different and higher osmotic pressure than 2-6 mm. is given 

 per 1 per cent, of haemoglobin, as in cases where the concentration 

 of Hb is more than 4 per cent. (Fig. 16) or the pigment is dissolved 

 in salt solution of greater dilution than 0-01 M (Fig. 17), Adair finds 

 a cause which satisfies him. If we accept his estimate, the value of n 

 would be 4 and the molecular weight of haemoglobin about 68,000. 



Turning from the osmotic pressure, another indirect method of 

 measuring the molecular weight would be by depression of the 



