Measurements of DC conductivity of suspensions in non aqueous media

The experimental determination of the electrical conductivity of very insulating liquids is as difficult as important in Electrohydrodynamics. Conductivity is a relevant property in many applications and basic phenomena. In colloidal suspensions the conductivity is directly related to the electrical and chemical relaxation times, the electrokinetic phenomena or the colloidal stability. Previous studies show the importance of measuring the dependency of the conductivity on the solid fraction of the particles, σ(φ). In this paper we present a set of measurements of the conductivity of a suspension of silica nanoparticles (with a diameter of the order of 30 nm) synthesized by the Stöberʹs method. The measurements are made with the help of a suitable device designed and built in our laboratory. The measurements have been done for up to 4% volume concentration, in a mixture of 70% of toluene and 30% of ethanol.