and must diffuse largely through the capillaries, a decided advantage may be gained through the use of vacuum drying.
CONCLUSIONSIdeal conditions for thermal drying are: using diminished pressure to minimize time of diffusion of deep-seated moisture; using properly desiccated air to sweep the water vapor from the drying chamber; and heating the specimen at a temperature as close as possible to that at which the rate of thermal decomposition becomes appreciable. These conditions provide the maximum difference between the vapor pressure of the water in or on the substance and that of the air in the dryer. It is the magnitude of this difference, together with changes in moisture-vapor diffusion rates, that determines the rate of drying and the degree of drying possible by thermal methods.