30 Chapter III 



less namely this. Assuming the truth of the equation we have all 

 the data for the determination of q. Now if our assumption is 

 correct we may determine q not merely from the values of K at 

 these two temperatures, but from the values of K at numerous other 

 temperatures; and the test lies in the fact that the values of q 

 so determined should all be identical, they being independent deter- 

 minations of a definite physical constant the heat of formation 

 of one gram-molecule of oxyhaemoglobin. Apart from the law of 

 mass action such an identity would be mere coincidence as unlikely 

 as if half a dozen church spires of different design taken at random 

 proved to be the same height. This test was applied; it was not 

 necessary to work out the whole curve in each case. Assuming 

 as a result of the law of mass action the hyperbolic nature of the 

 curve at each temperature, or, to put the matter in another way, 

 that K has a constant value for each curve, it was only necessary to 

 take one point at each temperature. The simple method of doing 

 this was to put a small quantity of haemoglobin solution into a flask 

 with a large quantity of an atmosphere containing but little oxygen, 

 and to determine the percentage saturation of the haemoglobin with 

 oxygen at several temperatures. The volume of gas must of necessity 

 be so large in comparison to that of the haemoglobin solution that 

 any reaction which takes place between the two may be regarded as 

 not altering the composition of the gas. Apart from the necessary 

 apparatus for blood gas analysis no further equipment was needed 

 for this experiment than a saucepan, a litre flask and a thermometer. 

 The saucepan lid was perforated to allow of the neck of the flask 

 protruding ; the flask was filled with nitrogen containing a small 

 quantity of oxygen ; about 10 c.c. of haemoglobin solution were put in. 

 The saucepan was filled with water which surrounded the flask, and 

 the lid was fixed immovably on the saucepan. At any temperature 

 it was a simple matter to establish an equilibrium between the 

 haemoglobin solution with its small volume and large surface and 

 the gas in the flask. When the equilibrium was once established the 

 apparatus was inverted. The solution ran down into the neck, where 

 it presented a very small surface to the atmosphere above it, and 

 therefore did not alter sensibly in percentage saturation whilst a 

 sample was being abstracted for analysis. Such an experiment 

 carried out at five different temperatures gave values as follows 

 for the percentage saturation : 



Temperature 16 24 32 38 49 



Percentage saturation ... 92 71 37 18 6 



