82 HAEMOGLOBIN 



the same time untouched by acid, for it very easUy deteriorates in 

 acid solution. The object is best attained by treating the haemo- 

 globin with carbonic acid, which, if bubbled long enough, seizes all 

 the sodium for the formation of sodium carbonate; this, as it ap- 

 pears, dialyses away. Having freed the ha3moglobin from sodium it 

 is then possible to dialyse it against distilled water, thus avoiding 

 questions of the unequal distribution of salts on either side of the 

 membrane. This operation is one of the greatest delicacy, as will be 

 gleaned from the following statement: "In one experiment traces 

 of carbon dioxide in the air, due to the respiration of a small sample 

 of fruit and vegetables placed in the same cold store, doubled the 

 osmometer readings within twenty-four hours (8)," 



The uniformity of Adair's results is remarkable considering the 

 difficulties against which he was working. 



The following table shows a series of experiments: 



In discussing Hiifner's results we said that a solution in which 

 each molecule had a weight of 17,000 grams would in theory yield 

 an osmotic pressure of 10 mm. for every per cent, of haemoglobin. 

 Adair's result is something quite different from that. It is lower 

 even than Waymouth Reid's and corresponds to a molecular weight 

 of approximately 67,000, i.e. to a molecule of Hb4(9). 



The fact that a dilute and strictly neutral haemoglobin solution 

 consists of molecules with an average molecular weight of some- 

 where in the region of 70,000 seems to be one of the fundamental 

 facts on which any theory of the nature of haemoglobin must be based. 



Having once attained that fixed point one may ask: What if the 

 solution is not dilute, and is not strictly neutral? What if it contains 

 salts? These three factors, salts, hydrogen-ion concentration and 

 haemoglobin concentration, have effects on the osmotic pressure which 



