Molecular heat of oxy haemoglobin 31 



Are these figures such as to give a constant value for q ? The 

 answer is as follows. If q were 28,700 the following would be the 

 percentage saturation : 



Temperature 16 24 32 38 49 



Percentage saturation... 90 71 41 22 6 



There is no greater divergence here than can be accounted 

 for by the error of the method used. A similar experiment, at a 

 much higher oxygen pressure, with a haemoglobin solution made in 

 a different way but also dialysed, yielded the following results : 



Temperature 16 25 32 38 



\ Observed . 96 89 77 52 



Percentage saturation j Caleulated ;- 9? 89 u - 4 



The value for q used in this calculation was 27,700. It seems 

 clear then, that as far as our present experimental methods will 

 carry us, q has a constant value of approximately 28,000 gram-calories 

 over a range of temperature of 16 to 49. 



There is never the same feeling of exhilaration about testing 

 known phenomena by known laws as there is about breaking abso- 

 lutely fresh ground. Though the conception which we were testing 

 had passed triumphantly through a successful ordeal, the research 

 which we are describing took on a new r and extremely interesting 

 aspect at this point, for now that the bonajlde nature of q seemed to 

 be established it was clear that we had hit upon a new method of 

 attacking the molecular weight, and this aroused our enthusiasm the 

 more as the molecular weight determinations of haemoglobin were in 

 a very chaotic condition. It is true that, shortly before his death, 

 HUfner <3) , in collaboration with Gansser, had made a determination by 

 a measurement of the osmotic pressure of haemoglobin. The haemo- 

 globin was placed in an osmometer which was permeable to salts; 

 the final osmotic pressure observed corresponded to a molecular 

 weight of about 16,000. In the performance of this experiment 

 Hiifner had assumed that the salts distributed themselves equally 

 on each side of the membrane. This assumption seems to be un- 

 justified, though the extent to which unequal distribution of the 

 salts would vitiate such a result has not been accurately ascertained. 

 Moreover others had attacked the same problem. Weymouth Reid (4) 

 and Roaf (5) had made similar experiments. The former arrived at 

 a value of 48,000, the latter at the conclusion that the value varied 

 within very wide limits according to the nature of the solvent used. 



