378 BULLETIN OF THE UNIVERSITY OF WISCONSIN. 



From the results of Landolt and Jahn and those of Nern"t 

 it appears that the dielectric constants at first increase with in- 

 crease of molecular weight and subsequently they decrease as the 

 molecular weight increases. Tomaszewski's values show an in- 

 crease with increase of molecular weight throughout. Regard- 

 less of which series of values for the dielectric constants is cor- 

 rect, the results show that these hydrocarbons do not follow the 

 rule observed in connection with most other homologous series 

 of compounds, — namely, that an increase in molecular weight 

 is accompanied by a decrease in the value of the dielectric con- 

 stant. 



The isomeric nitriles and alcohols have nearly the same di- 

 electric constants, the iso-compounds showing slightly higher 

 values. With the substituted ammonias the iso-compounds ex- 

 amined gave lower values than the normal compounds. 



A comparison of the values of the dielectric constants of the 

 alcohols and nitriles by means of Curves I and II shows that 

 for oscillations of high frequency the nitriles have higher values 

 throughout than the corresponding alcohols. For oscillations of 

 low frequency the values for the dielectric constants of the 

 higher members of the alcohol series are nearly the same as the 

 values found for the corresponding nitriles with high frequency 

 oscillations. [Compare curves Ha and I.] Since the nitriles 

 show but slight absorption, their dielectric constants when ex- 

 amined by other methods where slower vibrations are used will 

 probably agree closely with the values found with Drude's ap- 

 paratus. 



The marked effect of the presence of the cyanogen group in a 

 compound upon the value of its dielectric constant, is further il- 

 lustrated by comparing the dielectric constants of ethylacetate 

 (CH 3 COOC 2 H 5 ) and ethylcyanacetate (CH 2 CNC0 2 C 2 H 5 ), 

 for which Drude 1 found the values 5.85 and 26.7 respectively. 

 The values 26.5 and 65.3 here found for ethylcyanide (C 2 H 5 

 GN), and ethylene cyanide (C 2 H 4 (CN) 2 ), respectively also 

 exemplify this effect in a striking manner. Cyanogen itself, 



i Zeit. phys. Chem. pp. 308, 310, (1897). 



