Efficiency of crystallization

Table IV. Quantum Efficiency of Crystal Violet Formation...

The rate and efficiency of crystallization of calcium gluconate from solution following the electrode oxidation of glucose have been investigated, and this reaction at a platinum electrode is markedly catalysed by submonolayers of heavy metals (e.g, thallium,... 

The main difference between the two techniques is that in zone refining only a part of the charge is melted at any time. This change alone tremendously increases the efficiency of crystallization as a separation and purification method. An impurity travels with or opposite to the movement of the zone depending, respectively, on whether it lowers or raises the melting point of the substance to be purified. In this way the impurities are concentrated in one or... 

In order to make an efficient Y202 Eu ", it is necessary to start with weU-purifted yttrium and europium oxides or a weU-purifted coprecipitated oxide. Very small amounts of impurity ions, particularly other rare-earth ions, decrease the efficiency of this phosphor. Ce " is one of the most troublesome ions because it competes for the uv absorption and should be present at no more than about one part per million. Once purified, if not already coprecipitated, the oxides are dissolved in hydrochloric or nitric acid and then precipitated with oxaflc acid. This precipitate is then calcined, and fired at around 800°C to decompose the oxalate and form the oxide. EinaHy the oxide is fired usually in air at temperatures of 1500—1550°C in order to produce a good crystal stmcture and an efficient phosphor. This phosphor does not need to be further processed but may be milled for particle size control and/or screened to remove agglomerates which later show up as dark specks in the coating. 

Manufacture. Phosphoms pentachloride is manufactured by either batch or continuous processing. In the former, the phosphoms trichloride usually dissolves in carbon tetrachloride before being treated with chlorine. A mixture of ca one part of phosphoms trichloride to one part of carbon tetrachloride is introduced to a water-jacketed vessel that contains an efficient stirrer and a tight cover with a redux condenser. The chlorine is passed into the vessel below the Hquid level, and crystals of phosphoms pentachloride form in the Hquid. When the reaction is completed, the suspension of crystals of phosphoms pentachloride in the carbon tetrachloride is drawn out of the vessel and the crystals are filtered and then dried by circulating hot water through the jacket of the filter. The clarified carbon tetrachloride is returned to the reaction vessel. 

Mag., 25(1), 131 (1972)] conclude that these measurements are valid when 50 percent corrections are added for the bending energy of the crystal. Kuznetzov ranks other materials by a relative wear test. His results substantiate the efficiencies given earlier. Attempts to measure efficiency of the grinding process by calorimetiy involve errors that exceed the theoretical surface energy of the material being ground. 

Cerium is one of the most widely used activators, which improve the working characteristics of many scintillators. Determination of the valence state of cerium in single crystals of alkaline and rare-earth borates allows to establish the nature of activator centers for purposeful influence on the scintillation efficiency of the matrix. 

To increase the radiation absorption and ionization efficiency of IR YAG-Nd laser (wave length - 1064 nm) used in for analysis of synthetic oxide single crystals Bi Ge O, Li MoO, LiB O, the samples were grounded and pills of 010 mm were pressed and analyzed by LIMS EMAL-2 (Uki aine) ... 

Theoretical representation of the behaviour of a hydrocyclone requires adequate analysis of three distinct physical phenomenon taking place in these devices, viz. the understanding of fluid flow, its interactions with the dispersed solid phase and the quantification of shear induced attrition of crystals. Simplified analytical solutions to conservation of mass and momentum equations derived from the Navier-Stokes equation can be used to quantify fluid flow in the hydrocyclone. For dilute slurries, once bulk flow has been quantified in terms of spatial components of velocity, crystal motion can then be traced by balancing forces on the crystals themselves to map out their trajectories. The trajectories for different sizes can then be used to develop a separation efficiency curve, which quantifies performance of the vessel (Bloor and Ingham, 1987). In principle, population balances can be included for crystal attrition in the above description for developing a thorough mathematical model. 

The mixing coefficients a and b in (4.10) depend upon the efficiency of the spin-orbit coupling process, parameterized by the so-called spin-orbit coupling coefficient A (or for a single electron). As A O, so also do a or b. Spin-orbit coupling effects, especially for the first period transition elements, are rather small compared with either Coulomb or crystal-field effects, so the mixing coefficients a ox b are small. However, insofar that they are non-zero, we might write a transition moment as in Eq. (4.11). 

---