18 Prof. E. C. C. Baly on 



that the reactivity of a molecule will depend on the mole- 

 cular phase in which it exists, and further, the greater the 

 extent to which the condensation in the molecular force 

 field has taken place the smaller will be the reactivity. The 

 phase in which a molecule exists is governed by the nature 

 of the external force fields of its atoms. The more equally 

 balanced these are, the greater will be the condensation that 

 takes place between them. The particular phase assumed 

 by a molecule will depend on the external conditions such 

 as temperature, nature of solvent, etc. 



The experimental evidence in favour of the existence of 

 these molecular phases is exceedingly strong. It is not 

 possible to give here a detailed account of this evidence, but 

 two or three of the most striking observations may be 

 mentioned. For instance, it is common knowledge that 

 substances which possess very small reactivity are character- 

 ized by molecular frequencies which are large multiples of 

 their infra-red fundamentals and lie in the extreme ultra- 

 violet. The converse of this is also true, that substances 

 with measurable reactivity are characterized by frequencies 

 which relatively are smaller multiples of the infra-red 

 fundamental. Again, it is possible by changing the external 

 conditions of temperature or solvent to change the molecular 

 frequency exhibited by a given substance ; and in some cases 

 as many as six different molecular frequencies have been 

 brought into play, each of which is an exact multiple of the 

 infra-red fundamental of that substance. This means that six 

 different molecular phases of the same compound have been 

 observed. Then, again, it has been proved that a particular 

 frequency is associated with a specific chemical reactivity, 

 or, in other words, a particular molecular phase is endowed 

 with its own reactivity. It is manifestly impossible to 

 discuss in detail all the applications of this molecular phase 

 hypothesis within the limits of a few pages, and I propose 

 in this paper to select a few instances, and, in particular, to 

 deal with the energy changes which are involved in chemical 

 reaction. 



An interesting point arises at once when the force fields 

 of free elementary atoms are considered. It has been 

 assumed that in a molecular force field the force lines due to 

 the external faces of its atoms undergo condensation to form 

 a condensed molecular force field. It is manifest, if an atom 

 consist of a central positive nucleus with a single plane ring 

 of electrons, that the force lines at the two faces of fclistt 

 atom will be exactly equal and opposite, that condensation 

 must occur to form an atomic field of force, and that this 



