In this work, the density, viscosity, and electrical conductance of a ternary solution of {water + dextran + nicotinic acid} were determined experimentally. The data of electric conductance show that the dissociation of nicotinic acid is little influenced by the addition of dextran. The data of density indicate that with the addition of dextran a maximum of the solvation volume of nicotinic acid is observed The B-coefficient of viscous flow was evaluated from viscosity data Using Eyring's transition state treatment, the activation parameters of viscous flow, which reflect the effect of the concentration of dextran on the motion of nicotinic acid, have been obtained. The result shows that dextran impedes the movement of the molecular nicotinic add.