Simultaneous transport of nitric acid and sodium nitrate has been investigated in a batch cell with an anion-exchange membrane Neosepta-AFN. The transport of the individual components has been quantified by four phenomenological coefficients, which have been determined by the numerical integration of basic differential equations describing the time dependences of acid and salt concentrations in the low concentration compartment. This integration has been followed by an optimizing procedure. Using all the experimental data obtained at various initial concentrations of both components it has been found that the phenomenological coefficients are strongly dependent upon the concentrations of both components in the membrane. (C) 2011 Elsevier B.V. All rights reserved.