90 



Molecular Surface-Energy 

 fj. in Erg pro cm'. 



60'sr<i0'-30'2O'J0' 0' W2o-j(r ws(re<n(rsirsc'io(rmn{rx3tr/«i-/.'i(r/irw Temperature 

 Fig. 3. Tertiary Amines. 



On a comparison of the primary, secondary and tertiary amines 

 of the same alkyl-radical, it appears that the temperature-coefficients 

 of n are often analogous for 1""J and 3"''.v amines, but smaller than 

 those for the 2"'.'/ amines. 



However it becomes also clear, that a direct comparison of the 

 ft-<-curves with the aim of studying the influence of the substitution 

 by hydrocarbon-radicals in homologous compounds, may properly 

 be made only in the case of amines of the same fundamental con- 

 figuration ; as e.g. by comparison of all primary, or all secondary, 

 resp. tertiary amines, with each other, (fig. 1, 2 and 3). Really then 

 the regular increase of the values of ft in these cases, if substitution 

 occurs by more complicated hydrocarbon-radicals, comes to the fore 

 in a most striking way. 



With respect to the temperature-coefficients of f< it may be remarked 

 that these generally appear rather small; the smallest values being 

 present in the case of primary amines (1.2 — 1.8), while in the case 

 of secondary amines these values are often somewhat greater (1.7 — 2.3), 

 and just as with the tertiary amines, approach gi-adually to the 

 \'alues observed with other organic compounds. However, these rules 

 are no! without exceptions: e.g. in the case of (/miethylamine the 



