Crystallization development

Continuous vacuum pans have been successhiUy developed for raw sugar crystallization, and are widely appHed in South Africa, AustraHa, South America, and the United States. Continuous crystallizers, developed for beet sugar manufacture, are being adapted for use in cane sugar factories. 

Farrell, R.J. and Yen-Cheng Tsai, 1994. Nonlinear controller for batch crystallization Development and experimental demonstration. In American Institute of Chemical Engineers National meeting. Atlanta, Paper 89e. 

LaFs crystals developed by J. W. Ross and M. S. Frant as the first non-glass membrane electrode... 

BFR [Bleach filtrate recycle] A process for almost completely recycling the waste liquors from pulp-bleaching using chlorine dioxide. The key to the process is the separation of the sodium sulfate from potassium chloride by crystallization. Developed by Champion International Corporation, Sterling Pulp Chemicals, and Wheelabrator Technologies. It was proposed for installation in North Carolina in 1997. 

Birch, M., Fussell, S.J., Higginson, P.D., McDowall, N., Marziano, I., 2005, Towards a PAT-Based Strategy for Crystallization Development, Organic Process Research and Development, 9, 360-364. 

Crystals composed of the R and S enantiomers of the same racemic mixture must be related by mirror symmetry in terms of both their internal structure and external shape. Enantiomorphous crystals may be sorted visually only if the crystals develop recognizable hemihedral faces. [Opposite (hid) and (hkl) crystal faces are hemihedral if their surface structures are not related to each other by symmetry other than translation, in which case the crystal structure is polar along a vector joining the two faces. Under such circumstances the hemihedral (hkl) and (hkl) faces may not be morphologically equivalent.] It is well known that Pasteur s discovery of enantiomorphism through die asymmetric shape of die crystals of racemic sodium ammonium tartrate was due in part to a confluence of favorable circumstances. In the cold climate of Paris, Pasteur obtained crystals in the form of conglomerates. These crystals were large and exhibited easily seen hemihedral faces. In contrast, at temperatures above 27°C sodium ammonium tartrate forms a racemic compound. 

Figure 2.16 The CCC with a monochromating crystal, developed by Tanner and Bowen. The four-reflection Si 220 with single Ge 200 monochromating crystal is shown, for CuK 1...

Formation of band textures in HPC liquid crystalline solutions was studied by Navard (86) and Takaheshi et al. (94). Upon shearing, some polymeric liquid crystals develop a particular texture which is called "band texture" consisting of fine equidistant lines when viewed under crossed polars. In HPC-H2O mesomorphic solutions these bands are exhibited when the solution is allowed to freely relax after shearing. 

As the Beckmann rearrangement is believed to be a typical acid-catalysed reaction, many researchers have reported the relationship between the vapour phase reaction catalysis and the acidity of the catalysts tested on non-zeolitic catalysts - i2s- i3i. 318-334 and on zeolitic catalysts Another interesting point for the heterogeneous gas-phase Beckmann rearrangement is the location of the reaction on the catalyst and different studies have been published ° . The outer surface of the catalyst particle seems to be the most probable place for the Beckmann rearrangement supported by the traces of reagents, and notable amounts of by-products found only in the outer layers of the zeolite crystal. Development of new and more efficient catalysts have also been reported " . ... 

In 1830 del Rio read a paper on Becquerel s method of reducing silver ores (23). His paper (24) on the crystals developed in vermiculite by heat begins A pupil of the celebrated Werner, I have always been more of a Neptunian than a Plutonist, notwithstanding the many crystallizations produced in the dry way. A new instance which has come under my observation in the crystals of vermiculite has contributed materially to change my opinions.. . . ... 

Further cooling of the fuel leads to wax crystal formation throughout the fuel matrix. The growing wax crystals develop into a larger latticelike network encompassing the bulk fuel volume. This latticelike network eventually causes the fuel to become highly viscous and to eventually gel into a semisolid mass. The lowest temperature at which fuel remains in the liquid state just prior to gellation is called the pour point. 

Large short-prismatic quartz crystals develop toward the center of a void. In many cases, these crystals are amethyst, in which Brazil twins and Brewster fringes are universally observed. 

J. J. Watts and W. A. Richards patented the preparation of this salt by removing the proper quantity of carbon dioxide from sodium hydrocarbonate by adding sodium hydroxide, sodium carbonate, or the hydroxides of the alkaline earths, and crystallizing the soln. at about 35° C. Winkler obtained it from carbonated liquor of the ammonia-soda process and T. M. Chatard by the spontaneous evaporation of soln. of normal sodium carbonate which had been exposed to the air some time and thereby absorbed carbon dioxide. There is a fairly general agreement that a temp, below 35° is not favourable to the formation of trona and that the crystals develop better in sodium chloride soln. and excess of the normal carbonate also favours the formation of trona. J. J. Watts and W. A. Richards say that if an excess of the hydrocarbonate be used, it crystallizes out unchanged. T. M. Chatard studied the influence of the composition of the soln. on the formation of trona, and obtained the results indicated in Table LIV with soln. containing a mol. of the normal carbonate. H. N. McCoy and C. D. Test have studied the conditions under which the sesquiearbonate is formed, and their results are summarized in Fig. 73. 

Structure, then for every tetrahedron there is another tetrahedron which has the exact opposite orientation the electric fields of the dipoles compensate each other. If, however, all tetrahedra have the same orientation or some other mutual orientation that does not allow for a compensation, then the action of all dipoles adds up and the whole crystal becomes a dipole. Two opposite faces of the crystal develop opposite electric charges. Depending on the direction of the acting force, the faces being charged are either the two faces experiencing the pressure (longitudinal effect) or two other faces in a perpendicular or an inclined direction (transversal effect). 

This expression is not strictly correct, only at absolute zero is this state realized. With an increase of temperature, however, the free energy of the system decreases with increasing entropy. Therefore at higher temperatures, the crystal develops lattice defects in both the metal and oxygen sites, known as Schottky defects (see Section 1.3.2). 

Jensen, L. H, The structure of water in protein crystals. Developments in Biological Standardization, Vol. 74, p. 53-61. Acting Editors JoanC. May-F. Brown. S. Karger AG, CH-4009 Basel (Switzerland), 1992... 

The precipitation of calcium phosphate in the development of bone structure is a major topic beyond the scope of this discussion. It should be noted, however, that this process can be controlled by proteins and/or polysaccharides that provide sites for nucleation and that match features in the geometry of the crystal, such as repeat distances between certain groups. Other proteins can inhibit crystal development. Granular deposits of calcium involve small crystals so that deposition and reabsorption will be rapid. The size of the crystals can be controlled by their protein and/or polysaccharide environment, or even by a vesicular membrane which could act as a template. 

Smectic A liquid crystals are known to be rather sensitive to dilatations of the layers. As shown in [34, 35], a relative dilatation of less than 10-4 parallel to the layer normal suffices to cause an undulation instability of the smectic layers. Above this very small, but finite, critical dilatation the liquid crystal develops undulations of the layers to reduce the strain locally. Later on Oswald and Ben-Abraham considered dilated smectic A under shear [36], When a shear flow is applied (with a parallel orientation of the layers), the onset for undulations is unchanged only if the wave vector of the undulations points in the vorticity direction (a similar situation was later considered in [37]). Whenever this wave vector has a component in the flow direction, the onset of the undulation instability is increased by a portion proportional to the applied shear rate. 

In case the racemate is a true racemic mixture, this cannot be separated by preferential crystallization, but can be resolved using the diastereomer crystallization developed by Pasteur in 1848. A solution of the racemic mixture in water or methanol is allowed to react with a pure enantiomer (resolving agent), thereby forming a mixture of diastereomers that can be separated by crystallization. 

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