186 



HEMOGLOBIN 



Granting then that the data fit well enough to be applied to these 

 curves, we may proceed to calculate the heat of formation of haemo- 

 globin from the curves and to compare it with values obtained from 

 hyperbolic curves. 



Applying the data given above, namely, that at 64 per cent, satura- 

 tion the oxygen pressure at 26° C. is I2'5mm. and at 38° C. it is 31 mm., 

 the value of Q comes out to be 14,000 calories. The value given by 

 the "hyperbolic" calculation brought it out at 27,700. If, however, 

 our experimental technique had consisted not in measuring percentage 

 saturations at a given pressure but pressures at a given percentage 

 saturation (something in practice much more difficult), our calcula- 

 tion of Q would have been unaffected by the degree of inflection of 

 the ciu've. It should here be made very clear that Q is the heat 

 evolved when one molecule of oxygen unites with haemoglobin, it 

 makes no assumption as to the number of molecules of oxygen which 

 unite with one molecule of haemoglobin, nor is it a matter of any 

 interest now from that point of view for the molecular weight of 

 haemoglobin has been determined in other ways. 



If 32 grams or 22-4 Htres of oxygen give out 14,000 calories it 

 remains to calculate the quantity of heat given out by 1-34 c.c. of 

 oxygen when it unites with 1 gram of haemoglobin. That comes out 

 to -85 calorie, and the question must then be asked: How does that 

 figure compare with the experimental data? 



Many observers have determined experimentally the heat evolved 

 when haemoglobin unites with oxygen, and have arrived at very 

 varjdng results. Putting aside observations which have been made 

 upon blood, and considering only observations made on haemoglobin, 

 the following data are collected by Adolf and Henderson (lO): 



From the above data I learn that I enjoy the distinction of having 

 obtained a figure higher than that of any other observer — a cir- 

 cumstance which reminds me of the novel in which it is recorded of 



