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Crystallization (Intercrystalline)

Last updated: January 29, 2021

What Does Crystallization (Intercrystalline) Mean?

Crystallization is a naturally occurring solidification of molecules or atoms into a structured form or lattice, the result of which is then called a crystal.

Crystallization is also a laboratory or production separation technique whereby a solution is separated from a mother liquor to obtain solid products. The crystallization process is carefully controlled in order to meet the customer's demands for properties like particle size, distribution, crystal shape and purity. The particles must be easily separated from the mother liquor and meet the additional demands of filterability and washability.

Due to the mostly rigid structure of the solid phase, the formation of the solid particles can be a rather slow process, so large process vessels are typically required in order to reach an acceptable production rate.

Crystallization is sometimes used as a generic term for evaporative or cooling crystallization, melt crystallization, and precipitation crystallization. However, there are considerable differences seen between the three types of crystallization when it comes to their processing method and the corresponding required equipment.

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Corrosionpedia Explains Crystallization (Intercrystalline)

Crystallization is a natural process in which materials solidify from a liquid or precipitate out of a liquid or gas. This is caused by a physical change such as a temperature change, or by a chemical change such as a change in acidity.

How Crystallization Occurs

Crystals can form from a single species of atom, a variety of ion species, or even large molecules such as proteins. The crystallization process is directed by the size and shapes of the molecules involved and their chemical properties. Some large molecules undergoing the crystallization process may have a harder time due to their internal chemical asymmetry and their tendency to interact with themselves to avoid crystallization.

The smallest unit of a crystal is referred to as a unit cell, which makes up the base formation of atoms or molecules upon which additional units can then be attached. The unit cell essentially becomes a building block to which other blocks are then attached. Crystallization proceeds by attaching these blocks from all directions.

Different materials may form variously shaped crystals, which accounts for their great variation in shape, color and size.

Requirements for Crystallization to Occur

Two events must occur for the crystallization process to proceed. The first is the formation of an atomic or molecular cluster on a microscopic scale in a process known as nucleation. The second step in the process is a stabilization of the clusters that results in sufficiently large crystal growth.

Crystallization in Production and Manufacturing

Although crystallization can occur naturally, it is also used on a broad industrial scale as a separation and purification method in the pharmaceutical and chemical industries.

The most utilized crystallization process involves dissolving a solute in a solvent that is least partially soluble. Often the solution is heated to increase the solubility so that the maximum amount of solute may go into solution. The mixture is then filtered to remove undissolved material or impurities. The filtrate, which is the remaining solution, is then allowed to slowly cool, thus inducing crystallization.

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