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Vacuum drying is the mass transfer operation in which the moisture present in a substance, usually a wet solid, is removed by means of creating a vacuum. In chemical processing industries like food processing , pharmacology, agriculture, and textiles, drying is an essential unit operation to remove moisture. [ 1 ]
Freeze-drying is a special form of drying that removes all moisture and has less effect on the taste of food than normal dehydration. Freeze drying is a water removal process commonly used to preserve pear material. The fruit is placed in a vacuum chamber at low heat to increase shelf life.
Dielectric drying (radiofrequency or microwaves being absorbed inside the material) is the focus of intense research nowadays. It may be used to assist air drying or vacuum drying. Researchers have found that microwave finish drying speeds up the otherwise very low drying rate at the end of the classical drying methods.
A vacuum desiccator (left) and desiccator (right). Silica gel with cobalt chloride indicator placed in the lower shelf is used as the desiccant.. A desiccator is a heavy glass or plastic container, now somewhat antiquated, used in practical chemistry for drying or keeping small amounts of materials very dry.
De-watering: If low amount of product is found in very large volume of spent medium, the volume is reduced by removing water to concentrate the product. It is done by vacuum drying or reverse osmosis. Polishing of metabolites: this is the final step of making the product 98 to 100% pure.
Drying of solids can be brought about by storing the solid over a drying agent such as phosphorus pentoxide (P 2 O 5) or silica gel, storing in a drying oven/vacuum-drying oven, heating under a high vacuum or in a drying pistol, or to remove trace amounts of water, simply storing the solid in a glove box that has a dry atmosphere.
Many salts and solids can be dried using heat, or under vacuum. Desiccators can also be used to store reagents in dry conditions. Common desiccants include phosphorus pentoxide and silica gel. Chemists may also require dry glassware for sensitive reactions. This can be achieved by drying glassware in an oven, by flame, or under vacuum.
Forensic labs use vacuum ovens that have been configured in specific ways to assist in developing fingerprints. Gravity convection ovens are used for biological purposes such as removing biological contaminants from samples. Along with forced-air ovens, they are also used in environmental studies to dry out samples that have been taken.