the Unit-Steve Theory. 



337 



It will be noticed in the first place, that the volume of 

 CH 2 varies much less under these more precisely correspond- 

 ing conditions than at the boiling-point. Also the value of 

 6 V/W varies but slightly, and in any case, far from there 

 being a rise with complexity, there is a decrease. It is con- 

 cluded that the differences for CH 2 do not show the true 

 values of constitutive changes, but exaggerate them. They 

 may even be deceptive. For instance, suppose that V/W 

 should not be quite constant, but should reach a minimum 

 and then rise as the complexity increases, as is at any rate 

 probably the case near the critical point ; the differences 

 would not show a minimum but gradually rise to the end of 

 the series. This must necessarily happen under such condi- 

 tions, for a preliminary decrease of V/W w T ould cause a 

 depression of the differences between the whole molecular 

 volumes, while the subsequent increase in V/W would make 

 the differences between the whole molecular volumes of con- 

 secutive members of the series too great. 



The following table gives the values of V/W for the normal 

 paraffins at the boiling and the critical points : — 



XI.— Table showing the Values of V/W at the B.P. and the 

 Critical Point. 



No. 

 1. 



Hydrocarbon. 



W. 



26 



v BP' 



A- 



V/W. V K . 



A. 



V/W. 



n Butane, C 4 H 10 



96-0 





3-69 



251-0 





9-65 











21-8 







58-3 





2. 



n Pentane, C 5 H 2 



32 



117-8 



22-13 



3 68 ; 309-3 



56-8 



9-67 



3. 



n Hexane, C G H U 



38 



139-93 



22-63 



3-69 366-1 



602 



9-63 



4. 



n Heptane, C 7 H 1C 



44 



16256 



23-70 



3-69 426-3 



62-5 



9-69 



5. 



n Octane, C 8 H 18 



50 



186-26 





3-72 ; 488-9 





9-78 





Mean values . 





22-5 



3-69 



59-5 



9-68 













V/W is fairly constant both at the boiling and the critical 

 points. Octane, however, shows a higher value at both these 

 points. 



It is usually possible, by means of the independent method 

 adopted at the melting-point, to prove that the value of V/W 

 is in reality that of H. The results are only approximately 

 concordant, owing to the exaggerated deviations shown by 

 the differences for CH 2 . Nevertheless the method is suffi- 

 ciently good to exclude both Kopp and Schroder's constants. 



