A modified method has been suggested for the measurement of diffusivity in liquids. It is based on monitoring the concentration of the component in the external solution, which is in the contact with the solution inside the vertical bundle of the capillaries plugged at the lower ends. Using these dependences, diffusivity including its dependence upon the concentration of the component can be obtained by the numerical integration of the basic differential equation describing the concentration field of the component inside the capillaries followed by the optimizing procedure. Here, the whole procedure has been described in detail. The paper is focussed on the transformation of the errors of measurement of the concentration dependences into the final results. Using the published data on diffusivity of aqueous solutions of sulfuric acid, the precise so-called "experimental" data have been calculated and then small random errors have been introduced into them. This procedure has revealed that good results can be achieved with the set of precise experimental data consisting of several time series at various initial acid concentrations. (c) 2005 Elsevier B.V. All rights reserved.