Crystal continuous

Crystallization continues to be the most widely used method of separating or resolving enantiomers (optical resolutions). The manufacture of chemicals and pharmaceuticals as purified optical isomers, or enantiomers, has taken on a pivotal importance in the pharmaceutical, agricultural and fine chemicals industries over the past 15-20 years. Crystallization has been and continues to be the most widely used method of separating or resolving enantiomers (optical resolutions), and is particularly well suited to separations at large scale in manufacturing processes (Jacques etal., 1981 Roth etai, 1988 Wood, 1997 Cains, 1999). 

Let us examine the crystallization process of an initial composition Cl the first crystals to form are those of the pure component 2 (y", T = 1175 °C). Crystallization of y" drives the residual liquid radially away from corner 2 along direction 2-Cl, until peritectic curve PP is reached. Here, crystals y" react with the liquid and are transformed into intermediate compound C . Displacement along the peritectic curve terminates when all phase y" is completely resorbed. This occurs geometrically when trajectory C-Cl encounters peritectic curve PP. Crystallization of Cj then proceeds, while the residual liquid moves radially away from C . The liquid path then reaches cotectic curve E -Em and crystals y begin to precipitate in conjunction with Cj. Crystallization continues along the cotectic line and, at ternary eutectic Em, crystals y " precipitate together with C and y until the residual liquid is exhausted. 

The first satisfactory definition of crystal radius was given by Tosi (1964) In an ideal ionic crystal where every valence electron is supposed to remain localised on its parent ion, to each ion it can be associated a limit at which the wave function vanishes. The radial extension of the ion along the connection with its first neighbour can be considered as a measure of its dimension in the crystal (crystal radius). This concept is clearly displayed in figure 1.7A, in which the radial electron density distribution curves are shown for Na and Cl ions in NaCl. The nucleus of Cl is located at the origin on the abscissa axis and the nucleus of Na is positioned at the interionic distance experimentally observed for neighboring ions in NaCl. The superimposed radial density functions define an electron density minimum that limits the dimensions or crystal radii of the two ions. We also note that the radial distribution functions for the two ions in the crystal (continuous lines) are not identical to the radial distribution functions for the free ions (dashed lines). 

Every free valence has a mean lifetime that is, the valencies can appear and disappear. A crystal continually produces and absorbs free valencies. 

Sodium Carbonate Peroxohydraie. Known commeicially as sodium percarbonate. sodium carbonate peroxohydrate does not contain the C-O-O—C group and is not a peroxocarbonate. The stoichiometry is 2Na2C03 3H202. The material is made commercially by three processes batch crystallization, continuous crystallization, and fluid-bed reaction. 

At intermediate temperatures, i.e. at temperatures below the temperature corresponding to Mcrit=2,500 g mol-1, both components crystallised but in separate crystal lamellae. Crystallisation of the low molar mass component in the blend was promoted by the presence of crystals consisting of the high molar mass material. This finding was consistent with the crystal continuity between dominant and subsidiary crystals reported by Bassett et al. [46]. 

The intermediate phase—existing crystals continue to grow and new ones form. 

As the crystal is cooled below the phase transition temperature, the relaxation time decreases until it reaches a minimum, thenceforth it follows an Arrhenius law. It is therefore reasonable to assume that the minimum point coincides with the temperature at which the great majority of the Cu+ ions are at the low state. From this point onwards, as the crystal continues to be cooled, all the dipoles that are available to participate in the process are relaxing, yielding an Arrhenius relaxation time. Based on this argumentation, we claim that (vg/vf) in Eq. (127) is inversely proportional to the number of Cu+ ions that are in the low state such that... 

---