Crystallization concentration

Assumption 6. On the surfaces of the crystal, concentration of the corresponding substance in the solution corresponds to a saturated solution. 

The calculated concentration profiles in olivine and in the melt are shown in Figure 4-18. The mean length of the concentration profile in the crystal is very short, about 0.1 /rm, much shorter than the dissolution distance (48 /im) or =1.3 fim. Hence, the MgO deficiency of the profile in olivine is negligible compared to the amount of olivine dissolved. Therefore, during crystal dissolution, in calculating the parameter b = (wq Woo)/(w —Wq) should be the concentration of the initial or bulk crystal, not the interface crystal concentration, which makes the calculation simple. 

Figure 3. Wavelength dependence of the absorption coefficient (measured with light polarized perpendicular to the c-axis) of undoped and doped BaTi03 crystals. Concentrations refer to dopant atoms per BaTi03 formula unit in the melt.

B. Benzophenone cyanohydrin. To the 250-mL flask, which contains the crude 0-(trimethylsilyl)benzophenone cyanohydrin, is added 50 mL of tetrahydrofuran (Note 9), and 30 mL of 3 N hydrochloric acid. The mixture is heated at 65°C (oil bath temperature) for 1 hr. The solution is poured into a separatory funnel and 30 mL of water is added. The aqueous phase is separated and back-extracted with three 100-mL portions of diethyl ether. The ethereal extracts are combined with the tetrahydrofuran solution and dried over anhydrous magnesium sulfate, filtered, and the solvent is removed by evaporation on a rotary evaporator to give a yellow solid. The material is recrystallized from 300 mL of toluene and dried at a pressure of 0.05 mm overnight to give 17.7-18.8 g of white crystals. Concentration of the mother liquors to 100 mL produced a second crop of 1.1-3.8 g for a combined yield of 17.9-21.5 g (79-86%), mp 127-130°C (Note 10). 

In general terms the relations between possible compound phases in any system are determined by the usual tangent relation between their free energy surfaces. The free energy of any phase is a function of the temperature, activity of the components, number of lattice sites and relative numbers of atoms of each kind in the crystal, concentrations of vacancies, interstitials and substitutions of each kind, concentrations of associated defects, energies of lattice disorder, of defect interactions, of valence change, of ionization, etc. ... 

Separate off the toluene layer and dry over sodium sulfate. Filter the solution, then remove most of the solvent by rotary evaporation. Add petroleum ether to promote crystallization and filter off the crystals. Concentrate supernatant and add more petroleum ether and isolate a second crop of crystals. 

The influence of a shear field on emulsion crystallization is of great interest as it relates to behavior during product processing and distribution. Emulsions can be destabilized under shear in a controlled manner to deliver desirable properties uncontrolled or unintentional destabilization may lead to poor product performance. Comparisons of emulsions under perikinetic (at rest) and orthokinetic (under shear) conditions were made in an effort to understand the role of shear on the stability of the systems studied. Davies et al. (22) found stability of triglyceride emulsions containing crystals to be sensitive to both shear and crystal concentration. Crystal morphology also plays an important role in the destabilization of emulsions under shear. Boode and Walstra (4) reported the presence of needle-like... 

Direct contact with phenol crystals, concentrated solutions or vapors (45 ppm) causes serious damage to the eyes hyperalgesic chemical conjunctivitis, severe iritis, and possibly corneal opacification with loss of vision and edema of the eyelids. In some cases of poisoning through direct accidental eyelid contact, the seriousness of the injury to the eyelids has required surgery. ... 

In both the studies on basalts, the breaks in the slope of the log Pq vs. (1/T,K) curves occur at 20 to 30 volume percent of suspended crystals. The non-Newtonian behavior of these molten silicate suspensions appears to arise from the increasing concentration of suspended crystals in the melt. This suggests that in modeling fluid flow in silicate systems, power law behavior should be considered when the suspended crystal concentration exceeds 20 volume percent. 

The checkers obtained a yield of 48% from the first crop of crystals. Concentrating the mother liquor afforded additional crystals (total over 2 crops 59%)... 

Freeze concentration (during freezing, as water crystallizes, concentration of mAbs and any formulation stabilizer increases [e.g., 0.15 M sodium chloride in solution reaches 3 M at -10°C]. Buffers may preferentially crystallize leading to pH shifts.)... 

If the crystals arc anhydrous, calculation of the yield is simple, as the solid phase contains no solvent. When the crop contains water of crystallization, account must be taken of the water accompanying the crystals, since this water is not available for retaining solute in solution. Solubility data are usually given either in parts by mass of anhydrous material per hundred parts by mass of total solvent or in mass fraction anhydrous solute. These data ignore water of crystallization. The key to calculations of yields of hydrated solutes is to express all masses and concentrations in terms of hydrated salt and free water. Since it is this latter quantity that remains in the liquid phase during crystallization, concentrations or amounts based on free water can be subtracted to give a correct result. 

Figure 17 shows pans (F) and tubs (G) for crystallizing concentrated leachate. One hundred pounds of this concentrate yield about 70 pounds of crystalline saltpetre upon standing. 

FIGURE 17. Pans and tubs from crystallizing concentrated leachate for saltpetre (see Figure 16). One hundred pounds of the concentrate yields about 70 pounds of saltpetre (Ercker see Figure 5). 

I. A CSs or ether solution of Is is refluxed with excess As powder imtil the iodine color disappears. This is followed by rapid filtration. The product is then allowed to crystallize. Concentration of the solution yields additional crystals. The product is recrystallized from CSs or ether. 

As the crystal concentration Cx is only known at the gridpoints, this integral has to be evaluated numerically. The total concentration at position z can be calculated by averaging over the bed and crystal concentration... 

The shape factor a results from the particle volume m a = Kp/Z. In Fig. 8.3-7 the nucleation rate B related to the volumetric crystal concentration cpj (Pj = volume of all crystals/volume of the suspension) is plotted against the average rate of crystal growth with the average crystal size Z50 as a parameter. With the relation... 

Marsh BD, Philipp JR (1996) Three-dimensional magmatic filling of Basement sill revealed by unusual crystal concentrations. Antarctic J US 31(2) 39-40 Marsh BD, Zieg MJ (1997) The Dais layered intrusion A new discovery in the Basement sfil of the McMurdo dry valleys. Antarctic J US 32(5) 18-20... 

Batch vacuum crystallizer 0.035 kg/s of dry crystals of orange juice. Equipment 2.7 m diameter X 3.6 m long cylindrical vacuum chamber with 900 kW of ammonia refrigeration. Rate 0.5 mg water evap./s. Usually limited to crystal concentrations < 25 % w/w crystals. 

---