Critical anomaly of shear viscosity in a mixture with an ionic impurity

The effect of the ionic impurity (salt NaCl) on the critical behavior of the shear viscosity near the lower critical consulate point is studied for the mixture 3-methylpyridine + heavy water. The value of the viscosity critical exponent is found to be in agreement with the renormalization group prediction and almost the same as in the initial neutral mixture. Shrinkage of the asymptotic critical range and decrease of the critical amplitude of the viscosity caused by the ionic impurity are attributed to the increase in the size of the water-solute clusters.