Small-angle neutron scattering and Kirkwood-Buff integral study of aqueous solutions of pyridine

Solutions of pyridine in heavy water were studied by small-angle neutron scattering at 25 degreesC in the pyridine mole fraction range of 0.02-0.25. From the experimental data Kirkwood-Buff integrals and the closeness to phase separation parameters were calculated and compared with those obtained for pyridine - light water solutions from thermodynamic data available in the literature. The detailed analysis shows that a significant clustering of similar species occurs in the solution. In spite of the strongly non-ideal behavior these solutions are still far away from macroscopic phase separation. (C) 2004 Elsevier B.V. All rights reserved.