238 FEPORTS ON THE STATE OF SCIENCE. — 1920. 



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 characterised by frequencies which relatively are smaller multiples 

 of the infra-red fundamental. Again, it is jKDssible by changing the external 

 conditions of temperature or solvent to change the molecular frequency ex- 

 hibited by a given substance, and in some cases as many as six different mole- 

 cular 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. 



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 forco 

 lines at the two faces of that atom will be exactly equal and opposite, that 

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

 densation will be very great with the evolution of a large number of atomic 

 quanta. Such an atom will under ordinary circumstances possess little or 

 no power of attracting other atoms, and hence will have no measurable chemical 

 reactivity. It is possible that the atoms of the inactive gases, helium, neon, 

 &c., are of this type. On the other hand, if there exist more than one plane 

 orbit of electrons, a condition of asymmetry will be set up in the atomic force 

 field, with the result that the complete condensation to form a non-reactive 

 atomic field is no longer possible. It does not seem improbable that in the 

 various types of asymmetry likely to exist the explanation is to be found of 

 the various properties of elementary molecules which are familiar to the chemist. 

 The extreme conditions resulting from this asymmetry would be (1) the non- 

 reactive diatomic molecule such as H,, N„, &c. ; (2) the highly reactive mon- 

 atomic molecule such as Na, K. &c. ; (3) the highly reactive diatomic molecule 

 such as Fj ; (4) the non-reactive polyatomic molecule such as those of carbon. 

 Apart from this possibility, which need not now be discus.«!ed, it is necessary 

 to take into account the fact that at anv rate in the case of elementary molecules 

 containing more than two atoms the different molecular phases may be capable 

 of separate existence. Smits has put forward the theorv that the different 

 allotropic modifications of an element are equilibrium mixtures of different 

 molecular species of that element. Thus the various allotropic modifications 

 of sulphur are equilibrium mixtures of some or all of four molecular species 

 of sulphur known as ^x- P^. ^^. and 8,. There seems little doubt that 

 what Smits calls molecular species are in reality four different molecular 

 phases of sulphur, -which differ in their energy content by a definite number 

 of quanta at the infra-red fundamental of sulphur. It is of considerable interest 

 to note that each of the four varieties of the sulphur molecule exhibits a 

 different molecular frequency in the visible or ultra-violet region, and that 

 thev therefore conform to the definition of molecular phases. 



The molecular phase hypothesis throws a considerable light on the mechanism 

 of chemical reaction, and enables accurate calculations to be made of the com- 

 plete energy changes which are involved in any reaction. In the first place, 

 the calculation mav be made of the total energy which 1.=; evolved during the 

 combination of elementary atoms to form molecules which are in radiant 

 equilibrium with their surroundings. 



Let the case be considered of the combination of atoms of different elements, 

 and further let the characteristic frequencies of these atoms be 9x10'°, l'2xl0", 

 1-5 X 1011, and 2'1 x lO'i respectivelv. The least common multiple of these 

 four frequencies is l-2fi x 10", and this therefore will be the true molecular 

 frequency of the resulting molecule. On the assumption made in the preceding 

 paper that an equal amount of energy is contributed for each atomic frequencv, 

 the smallest eaual amount evolved for each atomic frequency is 1-26 x 6-56 y 10-'< 

 or S-?^?!^ V 10"''' ercT? The total ouantitv of enersv evolvd fh^refrirp in the 

 ac1>ual formation of each molecule will bp 4 x 8-2656 X 10"'^ or 3-30654 x 10"" ergs, 



