Crystallization Research Paper

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Crystallization: clustering, nucleation and crystal growth Introduction The process of Crystallization can be defined as "the understanding of intermolecular interactions in the context of crystal packing and the utilization of such understanding in the design of new solids with desired physical and chemical properties".4 Crystallization is also a chemical solid–liquid separation technique, in which mass transfer of a solute from the liquid solution to a pure solid crystalline phase occurs. Crystallization being a pervasive phenomenon, is a requisite process occurring in nature and many other chemical based food and pharmaceutical industries. Crystal formation is necessary for manufacturing of various pharmaceutical products, colorants,…show more content…
It is a phenomenon which requires superheating or super-cooling of the medium and occurs unsolicited & arbitrarily without any preferred nucleation site. Homogeneous nucleation prevails with much predicament in the interior of a uniform substance. The creation of a nucleus implies the formation of an interface at the boundaries of a new phase. On the contrary, Heterogeneous nucleation is a phenomenon occuring at the nucleation sites which have contact with the liquid or vapor. Many suspended particles or small bubbles can contribute to nucleation sites. Heterogeneous nucleation originates on extrinsic surfaces or particles, or seeding of nuclei of the new phase over the metastable old phase also known as secondary nucleation. Considering the crystallization of a saturated saline solution or a supercooled liquid can be triggered by adding just a few grains of the salt to the solution eg. ice-crystals. Heterogeneous nucleation typically has a much smaller barrier towards the phase transition and most phase transitions occurring in experiments or nature are started by heterogeneous…show more content…
For instance pure water may remain liquid at temperature below 0◦C, as long as its supercool temperature i.e. -42°C is not attained. Real-life examples of Nucleation • The formation of cloud is related to nucleation as when the air rises it entraps the small water molecules in it. As the temperature lowers the tendency of air to hold vapors reduces thus these water vapors nucleate to water droplets collectively forming clouds. This process following heterogeneous, begins on particles attributing to as cloud condensation nuclei, they enhance the cloud formation. • The process of Rock candy is based on a similar phenomenon, in which supersatured and boiling mixture of sugar molecules tends to crystal on a string or a stick upon dropping the temperature. A significant change in pressure tends to make the liquid superheated. • Furthermore a similar phenomenon can be seen in eukaryotic cells, where the process of Microtubule nucleation takes place with tubulin molecules which interact to form a microtubule seed. This being a spontaneously anomaly in purified tubulin solutions, appearances of molecular intermediates between tubulin dimers and microtubules can be
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