  We present an improved approach to the impedance spectroscopy of conductive
liquid samples using four-electrode measurements. Our method enables impedance
measurements of conductive liquids down to the sub-Hertz frequencies, avoiding
the electrode polarization effects that usually cripple standard impedance
analysers. We have successfully tested our apparatus with aqueous solutions of
potassium chloride and gelatin. The first substance has shown flat spectra from
$\sim$100 kHz down to sub-Hz range, while the results on gelatin clearly show
the existence of two distinct low frequency conductive relaxations.
