Abstract: Traditional measurement methods of diffusion coefficient have some defects, such as low accuracy, non-visual measurement, and critical environmental requirements. Therefore, a visualized measurement method of liquid diffusion coefficient based on a hollow right-angle triangle cell (RATC) has been provided. For this method, a linear laser is injected into the RATC filled by two kinds of liquid with different refractive indexes. The refractive index gradient generated by the liquid diffusion region can be visually reflected by the refractive spot after the laser passes through the RATC. For the refractive spot indicates the diffusion affecting on the refractive index, the equivalent interdiffusion coefficient of the two liquids is able to be calculated by combining the linear relationship between refractive index and concentration and the theoretical formula derived from Fick′s law. The experimental results show that the diffusion coefficient of 5.5mol/L glycerin solution is 7.47×10-10 m2/s, and the standard deviation of 125 groups of data is 7.12×10-12 m2/s. Meanwhile, the coefficient of variation is less than 1%, which shows that this method has strong consistency and high reliability.

Key words: diffusion coefficient, right-angle triangle cell, liquid refractive index, image processing