In this paper, the mixing process of two solutions of inorganic salts in a continuous flow channel with Y-type micromixer is investigated. Due to different diffusivity rates of solutes the double-diffusion convection develops in the channel. To visualize convective flows and the distribution of mixing substances the shear interferometer technique and a fluorescent dye are used. The latter makes it possible to quantify the mixing degree. The mixing extent for different volume flow rates is calculated. The comparison of convection and pure diffusion mechanisms of mixing is provided.