Precise and short-time measurement method of mass diffusion coefficients

A novel technique for short-time measurement of mass diffusion coefficients in transparent liquids using counter flow type diffusion cell has been proposed. This observation system was composed of a small transient diffusion cell and real-time phase shifting interferometer. The diffusion cell is specially designed to make a stepwise distribution of concentration as an initial condition for shortening measurement time. In order to obtain mass diffusion coefficients precisely from observed mass diffusion fields, several experimental conditions under which the formula for deriving mass diffusion coefficients was applicable were clarified from the viewpoint of theoretical approach. In the present experiments, small transient diffusion fields can be observed more clearly by means of real-time phase shifting interferometer and small diffusion cell in comparison with conventional method. The mass diffusion coefficients of water solutions of sodium chloride, sodium chlorate and l-alanine over a wide range of concentrations were derived from measurement data whose elapsed time is within 30 s. The uncertainty evaluation of present data is also carried out, and they are in good agreement with reference data found in literature derived by conventional methods within the maximum error of ±8.5%.