Crystallization practice crystal caking

With x-rays, however, one can have his cake and eat it too That the two conditions given above can both be met for a curved crystal was - appreciated first by Du Mond and Kirkpatrick18 and put into practice first by Johansson.21 This situation exists because-the crystal is a three-dimensional lattice of exceedingly small spacing. It is therefore possible to bend the crystal until the Bragg planes have the radius R,... 

In this country within the last few years an important improvement in process increases the yield of high purity crystals at the expense of those of low purity. Many salt wells contain measurable quantities of barium salts, which are decidedly poisonous and have caused much loss through the use for stock of low purity salt containing salts of barium. The improvement in process is purification by. precipitation of impurities. The brine as it comes from the wells receives a calculated quantity of salt cake (acid sodium sulphate), which, being a byproduct of nitric acid manufacture, is very cheap. The sulphuric-acid radical combines with the barium salts to form the insoluble barium sulphate, which is removed by a settling process and the practically barium-free brine concentrated as usual. Crystallization by concentration has been treated thus fully because it is a somewhat rare case. 

Sweeteners have other functions as well. They impart tenderness to cakes, thus enhancing their practical keeping quality. They increase the mobility of batters and the spread of cookies. The sirups increase moisture-retaining ability and retard crystallization of other sugars. 

Cakes containing particles of inorganic substances with sizes in excess of 100 /xm may be considered incompressible, for all practical purposes. Examples of incompressible cake-forming materials are sand and crystals of carbonates of calcium and sodium. The cakes containing particles of metal hydroxides, such as ferric hydroxide, cupric hydroxide, aluminum hydroxide, and sediments consisting of easy deforming aggregates, which are formed from primary fine crystals, are usually compressible. 

Uniform suspension is often the desired process result for process operations where a representative sample of solids is required or a uniform concentration of solids must be achieved. For example, in crystallization, nonuniform solids concentration may lead to unacceptably high local supersaturation levels and subsequent nonuniformity in crystal growth. Also, in as practical a way as possible, a slurry must be fed at a uniform solids concentration to a continuous reactor or to a centrifuge for uniform buildup of solids required for proper filtration and washing of the solid cake. 

Uniform suspension is required for crystallization, solid-catalyzed reactions, and suspension polymerization where high local concentrations may lead to poor yields of the desired product. Also, as practical as possible, crystallization slurries must be fed to a centrifuge at a uniform solids concentration for the proper cake buildup required for effective filtration and washing of the solid cake. 

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