318 DIRECT PROPERTIES OF MOLECULES 115 



that we have already ( 109) employed. This may be written 

 in the form 



wherein the value of s-, which may also be called the 

 diameter of the molecule, is expressed by magnitudes of 

 simple signification. Since j?7rs 3 is ( 109) the volume of the 

 molecular sphere, the product ^Trs^N denotes the space 

 actually occupied by the molecules contained in unit 

 volume. 



Let ft denote the ratio of this volume to the unit volume 

 in which the molecules are contained, or 



we shall with Loschmidt call it the coefficient of con- 

 densation, since underlying it is the meaning that it repre- 

 sents the extreme limit of possible condensation. We thus 

 obtain for the molecular radius the formula 



which allows the possibility of a calculation in absolute 

 measure, if we may assume that when a gas is transformed 

 into a liquid it has actually reached its maximum condensa- 

 tion ; for in this case the value of the coefficient of con- 

 densation would be given simply by the ratio of the 

 densities of the substance in the gaseous and liquid states. 



This assumption is certainly not free from doubt, since, 

 in the first place, the assumption of the spherical shape is 

 not justified, and in the second, as we have remarked in ihe 

 foregoing paragraph, the space required by a molecule in 

 the liquid state is possibly, or probably, not equal to the 

 extension of the molecule in space when actually in the 

 gaseous condition. The values of the coefficient of condensa- 

 tion t) so obtained will thus presumably be too large, and 

 this must also be true of the values of the molecular 

 diameter s which are calculated on this assumption. Such 

 a calculation is not, however, valueless, because it at least 

 shows us that the gaseous molecules must be less than a 

 certain magnitude which is expressed in absolute measure. 



