ABSTRACT Various solutions (Crank's) of Fick's law of diffusion have been used to predict moisture loss ( ML ) in osmotic dehydration, by correlating experimental data. Selection of a particular solution should depend on the sample geometry and the fulfillment of a number of assumptions made to obtain that solution. Crank developed solutions for long‐time, short‐time, and a solution for diffusion into a sample from a well‐stirred tank for sheets, cylinders and spheres. This work was carried out to find the most suitable Crank's solution to predict ML for a wide range of published data. The long‐time solution and the solution for a well‐agitated tank, for plane sheets, satisfactorily predicted ML of semi‐infinite sheets and semi‐infinite cylinders. PRACTICAL APPLICATIONS Crank's solutions of Fick's law for various geometric shapes are used in practice to determine the diffusivity from experimental data for unit operations governed by mass transfer. Once the diffusivity is known, those solutions can be used to predict the kinetics of mass transfer. One of the specific cases where this information is useful is in determining the loss of water for the process of osmotic dehydration. Crank developed solutions for several sets of initial and boundary conditions and for various product geometries. This article evaluates the suitability of Crank's solutions for a wide range of experimental data and indicates the most appropriate solution form to be used for each geometric shape.