Unit-Stere Theory of Molecular Volume. 601 



the molecular weights (M) form a series in arithmetical 

 progression with a constant difference 14 for CH 2 ; similarly 

 the sum of the valencies form another series in arithmetical 

 progression with constant difference 6 for CH 9 . Hence the 



M 



value of the second factor ™ for any member of an homo- 

 logous series of compounds is given by the quantity 

 + rc.l4)/(a'+rc. 6), 



where a = molecular weight of first member of the series 

 (e. g. CH 4 = 1() in the paraffins), n — number of CH 2 groups, 

 and a' = sum of valencies of the first member (<?. g. CH 4 = 6). 

 Now when n becomes large (i. e. when we are dealing 

 with a compound high in the homologous series) the values 



M 



of a and a' become insignificant, and the quantity ™. has a 



constant value — - or 2k\ so that the unit-stere of Le Bas 

 o 



= v x 2 J for all classes of compounds in homologous series. 



Le Bas bas shown that for paraffin hydrocarbons from 



CnH 24 to C ?5 H 72 the value of the stere at the melting-point 



is a constant, 



V M * 9.07 



or ,-^ = ==v= const. — >'\)1. 



w w 



M 



It has been shown that tt? is a const. = 233 for the high 



members in any homologous series, hence it follows that the 

 specific volumes should be constant. This is evident from 

 the table below. 



Hydrocarbon. 



v. 



M 



w' 



M 



. v. 

 W 



n H 24 



1-2910 



1-2935? 



1-2897 



1-2899 

 1-2887 

 1-2886 

 1-2875 

 1-2870 

 1-28(52 

 1-2855 

 1-2848 

 1-2849 

 1-2846 

 1-2843 

 1-2827 

 1-2807 

 1-2804 

 1-2795 



2-2941 2-962 



12 H 2B 



18 H 28 



2-2973 



2-3000 

 2-3023 

 2-3044 

 2-3062 

 2-3077 

 2-3091 

 2-3103 

 23115 

 2*3125 

 23135 

 23143 

 23151 

 2-3171 

 2-3192 

 2-3196 

 2-3208 



2-971 

 2-966 

 2 970 

 2-970 

 2-971 

 2-971 

 2-972 





o"h*° :::::::::::: 





c;!h 3 ' :::.:::::"■ 



oIh .:: ::: 





2-971 



&&:::.:::::::: 



2971 

 2-971 



C" H, 



2-972 

 2-971 

 2-97:: 

 2-972 

 2-970 

 2-970 

 2*969 



C„H " 





S^24 flio 



C.-H 





o s s ; I:: :::::::::::: 



C..H-., 







