Crystallization precipitation kinetics

The overall kinetics of crystal precipitation has to consider that the process consists of a series of consecutive processes in simple cases, the slowest is the rate determining step. Assuming the volume diffusion is not the rate determining step, we still have at least the following reaction sequences ... 

Heterogeneous crystallization is minimized by providing seed crystals for homogeneous crystallization (crystallization on the seed crystals) and by designing the reaction tanks so that the liquor leaving them is close to saturation and not highly supersaturated. This requires the knowledge of precipitation kinetics of calcium sulfate and sulfite. 

As stated above, control of the crystallization or precipitation process is essential to obtain crystals of biochemical compounds having appropriate properties. The phenomena, techniques, and analysis discussed in many of the previous chapters solubility and supersaturation, nucleation and growth kinetics, population balance methods, batch and continuous crystallizers, and factors governing crystal purity, habit and morphology are all relevant to the discussion of the crystallization of pharmaceuticals. We shall analyze the crystallization/precipitation of biomolecules in terms of these concepts. 

Matthew Marcus (center) received his PhD. in 1978from Harvard and joined Bell laboratories the same year. At Bell Labs, he worked on a variety of problems in materials science, with an emphasis on structure. Some of these problems include the structure of the liquid crystal blue phase, the precipitation kinetics of in Al films (probed by EXAFS), the relation between local structure and luminescence of Er in silica and silicon, and the structure and vibrations of nanoparticles of Au and CdSe. His contributions to EXAFS technique include methods for preparing samples and improved methods for fitting sets of data taken at different temperatures. In 1998, he left Bell Labs to work for KLA-Tencor, helping develop a new kind of PEEM-related electron microscope for wafer inspection. In 2001 he took on the position of Beamline Scientist at the Advanced Light Source, where he collaborates on environmental and materials problems using an X-ray microprobe. 

Even with the rapid progress currently underway in the modeling of velocity fields for fully turbulent flow, the real objective remains the process result. The critical physics lies in interactions between equations of motion and scalar transport and the kinetics of reactions, crystal precipitation and growth, and other core processes. These are coupled higher order sets of equations that need to be solved simultaneously in a truly rigorous solution. 

Much work is needed to elucidate the effects on metamorphic differentiation of rock plastic flow and fluid infiltration (see section on skarns below). Reaction rates and diffusion coefficiently are largely unknown for geological systems under metamorphic conditions (see Brady [46]). Experimental generation of mineral bands out of initially uniform aggregates of two or more kinds of crystals (even if these are not rock-forming minerals but substances with faster dissolution/precipitation kinetics) should be attempted. 

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