126 ORIGIN AND NATURE OF LIFE 



tude to ascribe the result to a residual 

 atomic affinity, which is absolutely powerless 

 to add another single atom to the molecule, 

 but can nevertheless set so large a store 

 of energy free by uniting with another 

 saturated molecule without any atomic dis- 

 placements. 



The experimental evidence is complete and 

 convincing that these saturated molecules 

 possess no remaining trace of atomic affinity, 

 and that the molecular unions must arise 

 not from atomic affinities, but from " mole- 

 cular affinities." 



Moreover, in such molecular combinations 

 between molecules behaving as units, there 

 are found properties which exactly reproduce 

 on the molecular scale, the analogues of the 

 " atomic affinities " and " atomic valencies " 

 described in the previous chapter, and these 

 it is proposed may be called " molecular 

 affinity " and " molecular valency." 



Such molecular affinity and valency do not 

 belong to any particular atom or group 

 in the molecule, but are a property of the 

 molecule as a whole. 



Molecular affinity is a specific property just 

 as is atomic affinity. Some pairs of molecules 

 will not unite, under ordinary circumstances, 

 to form molecular unions, so feeble is their 



