How to measure subdiffusion parameters.

We propose a method to measure the subdiffusion parameter alpha and subdiffusion coefficient Dalpha which are defined by means of the relation chi2 = 2Dalpha / Gamma(1+alpha)(t alpha), where chi2 denotes a mean square displacement of a random walker starting from x = 0 at the initial time t = 0. The method exploits a membrane system where a substance of interest is transported in a solvent from one vessel to another across a thin membrane which plays here only an auxiliary role. We experimentally study a diffusion of glucose and sucrose in a gel solvent, and we precisely determine the parameters alpha and Dalpha, using a fully analytic solution of the fractional subdiffusion equation.