Experiment 2

AIM :

To recrystallize given organic compound using alcohol as a solvent.

 APPARATUS REQUIRED :

• Given organic compound

• Alcohol

• Spatula

• Funnel

• Beaker

• Bunsen burner

• Filter paper

• China dish

• Wire gauge

• Stirring rod

• Water bath

• Tongs

THEORY :

Recrystallization is a purification technique which consists of dissolving the impure substances in a minimal volume of a solvent near its boiling point, then allowing the solution to cool slowly to recrystallize the substance and gets its pure crystals one more time.

The choice of solvents:

The solvent must be chosen to have the following properties:

• It dissolves the organic compound at the solvent boiling point does, it should not dissolve it at room temperature.

• A good solvent should be a better solvent for any impurities than it is for the desired compound at room temperature.

• The solvent has a low boiling point, which makes it easier to remove solvent traces from the purified solute crystals.

• It must not react with desired compound.

• It should not be expensive.

Purpose:

Recrystallization is a very important purification technique for purifying solid organic compounds. It is also used to manufacture the correct crystal size and shape.

An impure solid may be purified by first dissolving it in the minimum quantity of a boiling solvent.  Insoluble impurities are then removed by rapid filtration of the hot mixture. The filtrate is next allowed to cool slowly, crystals will form.

PROCEDURE :

• First take two spatula given organic compound in a beaker.

• Add 50 ml alcohol in the beaker and stir it little.

• Now take wire gauge and Bunsen burner, set it together and light up the burner.

• Put the water bath on wire gauge and heat it up to the water starts boiling.

• Now put beaker containing dissolved compound inside water bath using tongs.

• Take precautions that flames of burner doesn't comes in contact with the dissolved compound ( otherwise it will catch fire ).

• Now heat the beaker up to complete dissolution of solution.

• During heating constantly stir it.

• Take filter paper and set it inside funnel carefully ( ensure that there must be no space for filtrate  to get down without getting filter ).

• Put china dish below funnel, now pour filtrate from beaker to china dish through funnel carrying filter paper.

• When you get filtrate in china dish let it cool properly without disturbing for good crystals.

OBSERVATION :

• Weight of sample : 1g

• Color of sample : White crystalline compound 

• Yield of sample : 0.72g

RESULT :

• The compound gives white color crystalline solid.

PRECAUTIONS :

• Ensure that the crystals are washed well.

• Avoid overheating of  the solution.

• The filtrate should be evaporated slowly by gentle heating of the solution.

• The solution should be cooled slowly and do not any  rapid cooling.

• Wear safety gloves and safety glasses during doing experiment.