Kiteitys

Kiteitys, or crystallization, is a process by which a solid crystalline phase forms from a solution, melt, or gas. The resulting material has a highly ordered internal structure, known as a crystal lattice. Crystallization typically begins with nucleation, the formation of small crystal embryos, followed by crystal growth as molecules arrange themselves into the growing lattice. It can occur from solution, from a melt upon cooling, or by deposition from a gas in some cases.

Nucleation is a key aspect of kiteitys and can be homogeneous (occurring uniformly within the parent phase) or heterogeneous (occurring on surfaces or impurities). Primary nucleation happens without pre-existing crystals, while secondary nucleation generates new crystals from existing solid surfaces or fragments. Growth rates depend on factors such as supersaturation, temperature, solvent or melt properties, and the presence of impurities or seed crystals.

Common crystallization methods include cooling crystallization (reducing temperature to lower solubility), evaporation crystallization (removing solvent to increase supersaturation), and antisolvent crystallization (adding a solvent in which the solute is less soluble). Crystallization is widely used for purification and isolation of compounds, as well as for tailoring crystal size, habit, and polymorphism for downstream processing.

Critical factors in kiteitys are supersaturation control, temperature profile, solvent choice, impurities, and seeding. Process parameters such as agitation, residence time, and solvent exchange influence crystal size distribution and quality. Polymorphism and solvates pose challenges in pharmaceuticals and fine chemicals, requiring careful characterization and control. Common analytical tools include X-ray diffraction, optical and electron microscopy, and thermal analysis to assess crystallinity and polymorphs.