L is ] 



II. Lidlit Absorption and Fluorescence. — "VII. Molecular 

 Phases. By E. C. C. Baly, Grant Professor of Inorganic 

 Chemistry, University of Liverpool*. 



IN the preceding paper the combination of atoms to form 

 molecules was considered, and it was shown, on the 

 assumption that every elementary atom is characterized by 

 one or more elementary quanta of energy, that the resulting 

 molecule when freshly synthesized is characterized by a 

 molecular quantum of energy, and hence by a fundamental 

 frequency in the infra-red. The affinity of the atoms for 

 one another which causes the reaction to take place was not 

 discussed, and in the present paper I propose to deal with 

 this phenomenon, which, after all, is the fundamental 

 principle of chemical reaction and reactivity. 



In previous papers t I have suggested that chemical 

 reactivity has its origin in the electromagnetic force fields 

 of the atom, which, as will be shown below, condense to form 

 atomic and molecular force fields. In the papers referred 

 to it has been shown that these force fields are capable of 

 explaining all the chemical properties of substances. Al- 

 though this theory seemed to give a satisfactory explanation 

 of chemical reactivity, and one that to a certain extent was 

 quantitative, it lacked a complete quantitative basis. The 

 conception, however, of atomic and molecular quanta brought 

 forward in the preceding paper would appear capable of 

 supplying the necessary quantitative foundation. 



The electromagnetic force fields of atoms were first dealt 

 with by Humphreys J, who showed that they are capable of 

 giving a quantitative explanation of the Zeeman effect and 

 also of the pressure-shift of spectrum lines. He deduced 

 the fact that two atoms will attract one another when they 

 approach in such a way that the direction of their electronic 

 motions is the same, and will repel one another when their 

 electronic motions are in opposite directions. Each atom 

 therefore possesses tw r o faces, and when one pair of faces 

 comes together they attract one another, and when the other 

 pair comes together they repel one another. In other words, 

 an atom forms the centre of an electromagnetic field of force, 



* Communicated by the Author. 



t Trans. Chem. Soc. ci. pp. 1469, 1475 (1912), ciii. pp. 91, 20*5 

 (1913); Phil. Mag. xxvii. p. 632 (1914), xxix. p. 223 (1915), xxxi. 

 p. 417 (1916^ ; Astrophys. Journ. xlii. p. 4 (1915) ; J. Amer. Chem. 

 Soc. xxxvii. p. 979 (191o). 



X Astrophys. Journ. xxxiii. p. 233 (1906). 



