Mixed crystal

Foreign molecules in a host crystal are impurities when they are unwanted. Otherwise, they are guest molecules or dopants. In these cases, all the purification and growth methods can be applied in a corresponding manner. 

An interesting special case is exhibited by the the isotopic mixed crystals, e.g. perdeuteronaphthalene (GioDg) and naphthalene (GioHg), or perdeutero-anthracene (GuDio) and anthracene (CuHio). Here, the miscibility is nearly complete. When these crystals are grown from the melt, no noticeable separation of the 

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Fig. 11. Schematic diagram of a simple, perfectiy mixed crystallizer.

Determination of Crystallization Kinetics. Under steady-state conditions, the total number production rate of crystals in a perfectly mixed crystallizer is identical to the nucleation rate, B. Accordingly,... 

GSD Characteristics for MSMPR Crystallizers. The perfectiy mixed crystallizer described ia the preceding discussion is highly constrained and the form of crystal size distributions produced by such systems is fixed. Such distributions have the foUowiag characteristics. 

Preferential Removal of Crystals. Crystal size distributions produced ia a perfectiy mixed continuous crystallizer are highly constraiaed the form of the CSD ia such systems is determined entirely by the residence time distribution of a perfectly mixed crystallizer. Greater flexibiUty can be obtained through iatroduction of selective removal devices that alter the residence time distribution of materials flowing from the crystallizer. The... 

Classified removal of course material also can be used, as shown in Figure 16. In a crystallizer equipped with idealized classified-product removal, crystals above some size ate removed at a rate Z times the removal rate expected for a perfecdy mixed crystallizer, and crystals smaller than are not removed at all. Larger crystals can be removed selectively through the use of an elutriation leg, hydrocyclones, or screens. Using the analysis of classified-fines removal systems as a guide, it can be shown that the crystal population density within the crystallizer magma is given by the equations... 

Sodium chloride and sodium cyanide are isomorphous and form an unintermpted series of mixed crystals. The ferrocyanide ion has a marked effect on the habit of sodium cyanide crystallized from aqueous solution (50). Sodium cyanide and sodium carbonate form a molten eutectic at approximately 53 wt % sodium carbonate and 465°C. The specific conductivity of molten 98% sodium cyanide is 1.17 S /cm (51). 

This clearly indicates quantum diffusion of H and D atoms, rather than molecular diffusion. In mixed crystals of D2 and HD (with the H2/D2 ratio being from 20 1 to 7 1) the concentration of... 

Rielly and Marquis (2001) present a review of crystallizer fluid mechanics and draw attention to the inconsistency between the dependence of crystallization kinetic rates on local mean and turbulent velocity fields and the averaging assumptions of conventional well-mixed crystallizer models. 

This equation describes the change of population in a well-mixed system and is often used to model fully mixed crystallization and precipitation processes. If the system is imperfectly mixed, however, then the more complicated equation 2.88 can be used provided that the external flow field can be calculated e.g. by use of CFD (see later). 

Han, C.D., 1969. A control study of isothemial mixed crystallizers. Industrial and Engineering Chemistry Process Design and Development, 8, 150-158. 

A solution of p-nitro-N-phthaloyl-DL-phenylalanine (1.0 g) in methanol (25 ml) and a solution of cinchonidine (0.865 g) in methanol (30 ml) were mixed. Crystallization soon set in. The mixture was left overnight, and the colorless needles (0,97 g), MP 209° to 210°C, collected. After two recrystallizations from methanol the cinchonidine salt of the D-acid had MP 211°C,... 

To our knowledge Nikitin ao was the first to state that mixed hydrates should be described as mixed crystals of two hydrates. 

Radiation, chemistry, 191 resistance, 194, 199 Radical polymerization, 159 Relaxation times for mixed crystals, 191 Resonance, lines, 189, 190, 192, 202, 203 structures, 189... 

In certain cases, however, the solid which separates is a homogeneous mixture of both components, and hence may be referred to as a solid solution. These are often called mixed crystals, but the name is clearly unsuitable in view of the... 

Such a system is formed, for example, by a binary liquid mixture in contact with its vapour, or a mixed crystal in contact with its melt. 

The relations apply also to the case of a liquid mixture of two substances which is solidifying to a homogeneous solid which contains the two substances in proportions depending on the composition of the melt—a so-called solid solution or mixed crystal ( 138). 

Even higher temperatures are required for calcite dissociation. As f>co2 is increased to 760 Torr, the reaction temperature rises to 1170 K and the extent of dissociation is diminished [29]. The rate of decomposition of dolomite in vacuum [734] was intermediate between those for magnesite and calcite. Ranges of study were magnesite 810—870 K, dolomite 910— 990 K, and calcite 990—1050 K. Values of E were in the different sequence, magnesite < calcite < dolomite. Magnesite, which would decompose very rapidly at the temperature of dolomite dissociation, is, therefore, relatively stabilized, whereas the reactivity of calcite is enhanced in the mixed crystal. 

The magnetic properties of Pu compounds in different oxidation states are reviewed. New measurements on Pu(C8H8)2, PuFi, [(C2Hs)itN]2PuCl6, and [ (C2H5)itN]itPu(NCS)s are presented. The interpretation of the data is based on intermediate, j-j mixed crystal field states and orbital reduction due to covalency. Especially in the case of the organometallic compounds a large orbital reduction is found. 

Isomorphism. TiC is isomorphous with TiN and TiO. Thus oxygen and nitrogen as impurities, or as deliberate addition, can substitute for carbon to form binary and ternary solid solutions over a wide range of homogeneity. These solutions may be considered as Ti(C,N,0) mixed crystals. TiC forms solid solutions with the other monocarbides of Group IV and V. It is the host lattice for WC.li" ... 

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