| dc.description.abstract | Polar liquids like nitro-, chloro- and bromobenzenes find
possible applications in electrostatic generators, impulse voltmeters
etc. In this work natural conduction in these liquids
has been studied at electric fields of 50 V/cm to 50 kV/cm and
at temperatures of 0 to 200°C.
An all?glass vacuum system has been designed to distill
these liquids under a vacuum of 5 × 10?? torr. On fractional
freezing and continuous distillation the conductivities of these
liquids improved considerably. Since bromobenzene showed a
photo?conductive effect it was distilled in complete darkness.
Nitro-, chloro- and bromobenzenes showed minimum conductivities
of 6.6 × 10?²?, 2 × 10?²? and 1.25 × 10?²¹ mho/cm respectively,
after about one hundred hours of distillation.
Many theories have been proposed to explain the conduction
in insulating liquids under broad classification of dissociation
and emission theories. In liquids with high dielectric constants
the agreement between the various theories and the experimental
result is poor. A modification of the thermionic emission
theory has been suggested in this work and the current I and
stress E are shown to be related in the form:
log I = (e³E½ / 2kT) (1 + e?¹?)
in which e is the
electronic charge, ? the dielectric constant, k the Boltzmann
constant, T the absolute temperature and n a constant characteristic
of the liquid. The experimental results in nitro-, chloro- and bromobenzene
confirmed this equation. The results
in several other liquids by many previous workers also show good
agreement.
The conduction currents in these liquids increased with
the temperature according to I = exp(C ? Ea/kT) in which
Ea is the activation energy for electron release from its quasi?stable
traps. The activation energies for nitro-, chloro- and
bromobenzene were found to be 0.50 ± 0.05, 0.58 ± 0.06 and
0.38 ± 0.04 eV respectively. Data are not available in the
literature for comparison.
Ionic mobilities in these liquids have been deduced from
the time variation of the current following application of
a voltage to the liquids. These are found to be 12 × 10??,
6 × 10?? and 9 × 10?? cm²/V·sec in nitro-, chloro- and bromobenzenes
respectively at an electric stress of 3 kV/cm. These
are about a tenth of the values obtained in non?polar liquids.
The mobilities varied inversely with the electric stress in
all the three liquids. | |
