Critical properties and activation energy of nitrobenzene in N-alkanes solutions

The viscosity coefficient eta of nitrobenzene in n-octane and n-nonane solutions has been measured as a function of concentration and temperature. The coexistence curve, critical exponent beta and critical parameters of these solutions were determined. From experimental eta versus T-1 curves, and by applying the method of tangents, the activation energy of viscosity E is calculated as a function of concentration and temperature. The observed maximum in the curves of E versus the solute concentration (decreasing with increasing distance from the phase separation temperature) and particularly well marked in the critical region, is related to changes in the microstructure of the liquid appearing because of fluctuations in the critical region. The character of the temperature and concentration dependence of E was studied for nitrobenzene solutions in a few n-alkanes.