  Relative permittivities, $\varepsilon_{r}$, and refractive indixes, $n_{D}$,
have been measured at (288.15-308.15) K and (293.15-303.15) K, respectively,
for the mixtures 1-pentanol + octane, or + dibutyl ether and dibutyl ether +
octane. These data have been used, together with density measurements available
in the literature, to determine the correlation factor, $g_{K}$, for the
studied systems according to the Kirkwood-Fr\"ohlich equations. Results show
that the existence of cyclic species of 1-pentanol are predominant at low
concentrations of this alkanol when is mixed with octane. These species are
broken in large extent by the more active molecules of oxaalkane in the dibutyl
ether mixtures, which is in agreement with calorimetric data. The dibutyl ether
+ octane system does not show meaningful structure. These conclusions are
confirmed by values of the molar polarization and by the temperature dependence
of $\varepsilon_{r}$. The empirical expressions of Lorentz-Lorenz, Wiener,
Heller, Gladstone-Dale and Newton correlate well the $n_{D}$ data.
