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Calcinations is the process of subjecting a substance to the action of heat, but without fusion, for the purpose of causing some change in its physical or chemical constitution. The objects of calcination are usually: (1) to drive off water, present as absorbed moisture, as "water of crystallization," or as "water of constitution"; (2) to drive off carbon dioxide, sulphl11' dioxide, or other volatile constituent; (3) to oxidize a part or the whole of the substance. 'there are a few other purposes for which calcination is employed in special cases, and these will be mentioned in their propel' places. The process is often called "roasting," "firing," or "burning," by the workmen. It is carried on in furnaces, retorts, or kilns, and very often the material is raked over or stirred, during the process, to secure uniformity in the product.
Muffle furnaces (Fig. 10) are so constructed that neither the fuelnor the fire gases come in direct contact with the material to be calcined. A retort (A) of iron, brickwork, or fire-clay, is placed over the fire grate (G). Flues (F. F) are built around the retort, and through these the hot gases from the fire pass on their way tothe chimney (E).
Organic Chemistry for the industry
Inorganic Chemistry for the industry