When Case 1 of liquid diffusion is controlling during the falling-rate period, the time for drying can be determined from (3) under Example 18.13. Using that equation, derive an equation for the rate of drying to show that it varies inversely with the square of the thickness of the solid. If capillary movement controls the falling-rate period, an equation for the rate of drying can be derived by assuming the laminar flow of moisture takes place from the interior of the solid to the surface such that the rate of drying varies linearly with the average free-moisture content. If so, derive equations for the rate of drying and the time for drying in the falling-rate period to show that the rate of drying is inversely proportional to just the thickness of the solid. Outline an experimental procedure that could be used to determine whether diffusion or capillary flow governed in a given material.