A Method for the Determination of Mutual Diffusion Coefficients of Electrolytes in Water by Means of Conductivity Measurements

Abstract

Abstract A method for determining diffusion coefficients of electrolytes was studied by the use of a conductance cell made of a Pyrex glass tube (4–7 cm in diameter and 6.5 cm in length). A pair of platinized platinum electrodes are sealed into the tube at a position 10 mm below the top of the glass tube. The diffusion was carried out from solution in the cell to an outer solvent, and the rate was measured from the decrease in conductance at a fixed position in the cell. In the graphical relation between the measured diffusion coefficient and the time, the differential diffusion coefficient at the initial concentration of the diffusing solution was estimated by extrapolation of the linear portion of the plot to time→0. The differential diffusion coefficients obtained in 0.1 mol dm−3 solutions at 25 °C were as follows: HCl, (3.12±0.08)×10−5; KI, (1.909±0.020)×10−5; NaCl, (1.520±0.016)×10−5; 1/2Na2SO4, (1.059±0.028)×10−5; CuSO4, (0.610±0.033)×10−5 cm2 s−1.