The diffusion process is very important in many engineering applications. However, there is a shortage of data about diffusion, especially between liquid mixtures (such as water and glycerin, water and salt, etc.), which justifies the search for simple and accurate experimental techniques.

Optical techniques are recognized as powerful tools to investigate fluid flow phenomena in transparent media.

The aim of this paper is the development of an optical experimental technique, based on Diffractive Optical Element (DOE) Schardin’s schlieren # 2, for measuring liquid diffusion coefficient. This technique is then coupled to a new data treatment, based on correlation algorithms of the Particle Image Velocimetry (PIV) type, allowing the use of displacements recorded in the entire cell rather than just between two points.

Principles of the method and preliminary experimental results for the diffusion of a 1.75 M (moles/l) aqueous solution of common salt (NaCl) in pure water are given. These results are in good agreement with the literature.

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