crystallization

Name: layan shinanah
Subject : chemistry
Presented to :Ms. Juline Daibes
Date : 13,10,2015
Crystallization definition : to change into a solid form that is made up of crystal to cause (something, such as an idea, belief, etc.) to become clear and fully formed.

What Happens During a Crystallization :
To crystallize an impure, solid compound, add just enough hot solvent to it to completely dissolve it. The flask then contains a hot solution, in which solute molecules - both the desired compound and impurities - move freely among the hot solvent molecules. As the solution cools, the solvent can no longer hold all of the solute molecules, and they begin to leave the solution and form solid crystals. During this cooling, each solute molecule in turn approaches a growing crystal and rests on the crystal surface. If the geometry of the molecule fits that of the crystal, it will be more likely to remain on the crystal than it is to go back into the solution. Therefore, each growing crystal consists of only one type of molecule, the solute. After the solution has come to room temperature, it is carefully set in an ice bath to complete the crystallization process. The chilled solution is then filtered to isolate the pure crystals and the crystals are rinsed with chilled solvent.

How To Do a Crystallization :

Heat some solvent to boiling (remember to use a boiling chip). Place the solid to be recrystallized in an Erlenmeyer flask.

Pour a small amount of the hot solvent into the flask containing the solid.
Swirl the flask to dissolve the solid.

Place the flask on the steam bath to keep the solution warm.

If the solid is still not dissolved, add a tiny amount more solvent and swirl again.

When the solid is all in solution, set it on the bench top. Do not disturb it!

After a while, crystals should appear in the flask.

You can now place the flask in an ice bath to finish the crystallization process.

You are now ready to filter the solution to isolate the crystals. Please see the section on vacuum filtration. Remove the filter paper from the Buchner funnel when done.

After your crystals are filtered from the solution, put them on a watch glass.

Let the crystal finish drying on the watchglass.

uses in our life:
Crystals and gemstones have long been used throughout history for different purposes. Ancient Egyptians used carnelian for protection. The Greeks used amethyst to ease hangovers. The Chinese used Jade for healing their kidneys.
More recently, crystals were used as healing modalities in Europe from the 11th century through the Renaissance. Rulers also wore precious stones in their crowns, not for their opulent appearance, but for their trusted protective and spiritual properties.
As such, crystals are making a comeback! Here’s how you can use them in your daily life. Just remember to use these as a compliment to other traditional methods, especially if you’re going to be using stones to aid in physical ailments.

advantages and disadvantages:
One disadvantage is that the recovery of the materials in relatively pure form is usually not quantitative (that is, some material is lost, since as concentration decreases the ability to recover pure material also decreases).
Another disadvantage is the requirement for fairly large amounts of solvents, both for the process and for washing the crystals. Also, repetitive crystallizations are needed to achieve the best possible yield.

Crystallization is beneficial over other separation techniques because:
The produced crystals do not contain impurities (e.g. water, reagents etc). They are pure.
2. The crystals are the most concentrated form of the chemical possible.
3. Crystals can help in formulation (e.g. drug chemicals into tablets/capsules).

Why does crystallization separate mixtures?
Crystallization separates mixtures because the components have different solubility at high and low temperatures.
Crystallization is the slow precipitation of crystals from a saturated solution.
When it is used to purify an impure solid, the process is often called fractional crystallization or re crystallization.
You heat a sample of the impure compound with a suitable solvent, often at its boiling point.
Then you add enough extra solvent until the solid just dissolves. At this point, the solution is saturated.
As the solution gradually cools, the solubility of the compound decreases. Crystals of the pure compound precipitate out.
When you filter the cold mixture, crystals of the pure compound remain on the filter paper. The solvent containing the impurity passes through.

tools which are used in crystallization: in the crystallization experiment we actually used a beaker to put the salt and the water in it and we used the freezer to crystallize

History : crystallization has been known since 1840 and can prove to be straightforward but, in most cases, it constitutes a real bottleneck. This stimulated the birth of the biocrystallogenesis field with both 'practical' and 'basic' science aims. In the early years of biochemistry, crystallization was a tool for the preparation of biological substances. Today, biocrystallogenesis aims to provide efficient methods for crystal fabrication and a means to optimize crystal quality for X-ray crystallography. The historical development of crystallization methods for structural biology occurred first in conjunction with that of biochemical and genetic methods for macromolecule production, then with the development of structure determination methodologies and, recently, with routine access to synchrotron X-ray sources. Previously, the identification of conditions that sustain crystal growth occurred mostly empirically but, in recent decades, this has moved progressively towards more rationality as a result of a deeper understanding of the physical chemistry of protein crystal growth and the use of idea-driven screening and high-throughput procedures. Protein and nucleic acid engineering procedures to facilitate crystallization, as well as crystallization methods in gelled-media or by counter-diffusion, represent recent important achievements, although the underlying concepts are old. The new nanotechnologies have brought a significant improvement in the practice of protein crystallization. Today, the increasing number of crystal structures deposited in the Protein Data Bank could mean that crystallization is no longer a bottleneck. This is not the case, however, because structural biology projects always become more challenging and thereby require adapted methods to enable the growth of the appropriate crystals, notably macromolecular assemblages.