MOLECULAR VOLUME THEORIES AND 

 THEIR RELATION TO CURRENT CON- 

 CEPTIONS OF LIQUID STRUCTURE 



By GERVAISE LE BAS, B.Sc. (Lond.) 



There can be no doubt that of all the Properties of Matter 

 which have been correlated with the Chemical Structure of 

 the Molecules, Molecular Volumes have been of little use to 

 the chemist in his endeavour to determine the manner in 

 which the atoms are arranged in these structures. Many 

 successful attempts have been made with other physical pro- 

 perties, such as Optical Refractivity, the Magnetic Rotatory 

 Power, Viscosity, and so on, but this success has not attended 

 the study of Molecular Volumes. The reason for this seems 

 to be that the introduction of the conception of a co-volume 

 or molecular vibration volume into modern theories has exer- 

 cised a retarding effect, in that it has side-tracked the subject 

 from the main line of its historical development. It is possible 

 to show that, even supposing such a theory of liquid structure 

 as we have indicated should turn out to be based on fact, no 

 possible reason exists why the original point of view of Kopp 

 should be abandoned, for in any case, as Kopp supposed, the 

 volumes of the molecules at the normal boiling point are 

 approximately equal multiples of their real molecular volumes. 

 In these circumstances, important results from the point of 

 view of molecular structure may be expected if constitutive 

 influences be considered. 



Two types of Liquid Structure may be considered. 



(a) Space completely filled by matter. — This condition assumes 

 that the atoms of a molecule are in constant vibration about 

 a mean position, which is determined by the combined influ- 

 ence of the chemical forces of affinity and the expanding heat 

 forces. The atoms are regarded as those separate entities 

 which by combination make up the molecules, but which are in 

 actual contact at — 273 C. The effect of the vibratory motion 

 43 66 3 



