Calibration and Validation of Diaphragm Cell for Measuring the Diffusion Coefficient of Liquids

In simulation and modeling of mass transfer phenomena, design of separation equipment; and predicting the mass transfer of miscible fuels, the mass transfer coefficients is required. In this study, a diaphragm-cell was manufactured to measure the liquid-liquid diffusion coefficient. The cell constant was obtained to be 0.188 cm-2 with 0.5 molar solution of potassium chloride solution. Based on this value, the binary diffusion coefficients of 0.5 molar sodium chloride and heptane-benzene solutions were obtained as 1.6×10-5 and 2.38×10-5 cm-2/s at 25 °C, respectively. These coefficients have been previously reported respectively as 1.5×10-5 and 2.29×10-5 cm2/s at 25 °C. Afterward, the infinite dilution diffusion coefficients of heptane in benzene and benzene in heptane at 25 °C were obtained as 3.14×10-5 and 1.88×10-5 cm2/s, respectively. These coefficients have also been previously reported as 3.4×10-5 and 2.10×10-5 cm-2/s respectively. The measured diffusion coefficients showed a good agreement with literature values. Finally, investigating the effect of liquid density of upper and lower part of the diaphragm cell on the measured value of diffusion coefficient showed that the solution with higher density should be charged in the lower part of the cell.