Electrical conductance and volumetric studies in aqueous solutions of nicotinic acid

Conductivity measurements of nicotinic acid and sodium nicotinate in dilute aqueous solutions were performed in the (288.15 to 323.15) K temperature range. The limiting equivalent conductances of the nicotinate anion, λ ⁰(Nic^-, T), and the dissociation constants of nicotinic acid, K(T), were derived by the use of the Onsager and the Quint and Viallard conductivity equations. Densities of aqueous solutions with molalities lower than 0.2 mol-kg^-1 were determined at 5 K temperature intervals, from T = (288.15 to 333.15) K. The measured densities were used to evaluate the apparent molar volumes, V _{2, φ}(m, T), the cubic expansion coefficients, α(m, T), and the changes of isobaric heat capacities with respect to pressure, (∂C_P/∂p)_{T, m} . They were qualitatively correlated with the changes in the structure of water when nicotinic acid is dissolved in it.