Thin material, drying

A thin slab of solid material dries first by evaporation from the top surface and then by diffusion from the interior of the solid. The water movement is approximated by the diffusion equation... 

When drying thin material, there is little effect on the drying time by friction due to flow in the capillaries. In many of these cases the effect of gravity is negligible and there will be no moisture gradient within the solid. 

Frequently it is possible to extract the volatile components directly from the intact food or plant material. This is particularly true with thin materials such as leaves or relatively dry powders such as ground coffee, tea or wheat flour. More often it is necessary to drop or grind the material in some way (e.g. with a blender) to put it into a finely divided form. Sometimes with dry materials a Soxhlet apparatus is used (5). With highly aqueous materials such as fruits and vegetables, a continuous liquid-liquid extractor can be used (on the blended filtered product). 

X.D. Chen, The basics of a reaction engineering approach to modeling air-drying of small droplets or thin-layer materials. Drying Technology, 26 (2008) 627-639. 

However, it is useful for very thin materials and nonstandard-size panels in small lot sizes. With automatic equipment, the basics are the same but the panel enters from an automatic loader or a conveyorized preclean tool directly into and throngh the dry-film laminator. 

Alkvl Azides from Alkyl Bromides and Sodium Azide General procedure for the synthesis of alkyl azides. In a typical experiment, benzyl bromide (360 mg, 2.1 mmol) in petroleum ether (3 mL) and sodium azide (180 mg, 2.76 mmol) in water (3 mL) are admixed in a round-bottomed flask. To this stirred solution, pillared clay (100 mg) is added and the reaction mixture is refluxed with constant stirring at 90-100 C until all the starting material is consumed, as obsen/ed by thin layer chromatographv using pure hexane as solvent. The reaction is quenched with water and the product extracted into ether. The ether extracts are washed with water and the organic layer dried over sodium sulfate. The removal of solvent under reduced pressure affords the pure alkyl azides as confirmed by the spectral analysis. ... 

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