Recrystallization: 5 Points That You Should Know

Recrystallization, also known as fractional crystallization, is a powerful purification technique and is often applied in the chemical industry, pharmaceutical industry and probably in breaking bad to make other stuff. How does this technique work and what is it? We will address the following topics in this blog;

• What is recrystallization?
• How does recrystallization work?
• What are the advantages of recrystallization?
• What are the disadvantages of recrystallization?
• What can actually be removed with recrystallization and from what?

“Especially with organic synthesis recrystallization a frequently used purification technique "

What is recrystallization?

In chemistry, and especially with organic synthesis and analytical chemistry, recrystallization is an often applied purification technique. The recrystallization procedure is that a material is dissolved and re-crystallized under other conditions to reach higher purity levels.

The recrystallization definition according to the dictionary is: "t o become crystallized again ".

How does recrystallization work?

In the case of recrystallization, the recrystallization procedure is that one solidifies crystallized material and this is finally crystallized again to obtain the final product; crystals with the desired size, shape, purity and yield. The underlying mechanisms, dissolution and recrystallization can also minimize the internal energy of the crystal so that a better energy balance is achieved, resulting in a stable polymorphic product. Usually, recrystallization is intentionally applied to crystals and processes to optimize these. The method works based on the principle that the recrystallizing substance is low soluble in a given solvent at a low temperature(e.g. ethanol or acetone), but much more soluble at higher temperature.

There are various recrystallization methods like;

• Single-solvent recrystallization
• Multi-solvent recrystallization
• Hot filtration-recrystallization
• Single perfect crystals (for X-ray analysis)
• Seeding

What are the benefits of  recrystallization?

• To achieve high efficiency, the purification technique works especially well when the difference in solubility between hot and cold large is.
• Organic chemistry, very good to apply technique in organic chemistry.

What are the disadvantages of recrystallization?

• Unwanted or by-products, uncontrolled recrystallization can cause the undesired production of hydrates and solvents or polymorphic transformations.
• Much research needed (high costs and a lot of time), choosing the right solvent is therefore important and this usually requires a lot research.

What can be purified with recrystallization?

Various products become, through recrystallization, purified in the chemical and pharmaceutical industry in particular;

• Salicylic acid (painkiller)
• Benzoic acid (food additive, E210)
• Cocaine (stimulant that belongs to the alkaloids)
• Potassium perchlorate (very powerful oxidizer)

Melting is a variant of recrystallization and this is mainly used as a purification technique for silicon and other semiconductors for making various electronic components.

In this blog we discussed the basics of the purification technique recrystallization. We have discussed the following themes; what is recrystallization, how does recrystallization work, what are the advantages and disadvantages of recrystallization and what can actually be removed with recrystallization. Also read our other and future blogs about various purification techniques.