MOLECULAR ARCHITECTURE 



365 



determined near their melting-points, of the members of a 

 number of homologous series of organic substances, this worker 

 has come to the conclusion that in these compounds the mole- 

 cular volume is proportional to the valency volume calculated 

 according to the Barlow-Pope method, each carbon atom being 

 supposed to occupy a volume four times that of a hydrogen atom ; 

 further that, at any rate in the case of higher members of such 

 series, the absolute volumes of the atomic spheres are unchanged 

 in the passage from one member to another. The molecular 

 volume of any compound can be regarded as the sum of the 

 volumes of the spheres of influence of the atoms contained in 

 the molecule. It follows that if the molecular volume V be 

 divided by the valency volume W, the quotient obtained is the 

 volume of a unit or hydrogen sphere. This unit has been termed 

 a " stere " ; the following table shows how remarkably constant 

 is its value throughout the paraffin series of hydrocarbons. 

 The mean value of the stere for this series is 2*970 ; by multi- 

 plying this number by JV, the molecular volume for any hydro- 

 carbon of the series can be calculated ; the calculated values, as 

 can be seen from the table, approximate very closely to those 

 obtained experimentally. 



Molecular Volumes of the Normal Paraffins 

 AT their Melting Points. 



Mean Values 



17-83 



2-970. 



This investigation furnishes positive proof that in this series 

 the volumes appropriated by the carbon and hydrogen atoms 



