Experiment 1

AIM :

•  To recrystallize the given  organic compound using water as a solvent.

APPARATUS REQUIRED :

• Sample of compound    

• Beaker

• Water

• Spatula

• Glass rod

• China dish

• Tripod stand

• Burner

• Wire gauge

• Filter Paper

THEORY :

Organic compounds synthesized in the laboratory or isolated from natural sources are often contaminated with impurities. Recrystallization is a widely used purification technique for removing impurities from organic compounds that are solid at room temperature. This method relies on the observation that the solubility of a compound in a solvent generally increases with temperature. Conversely, as a solution cools the solubility of a compound will decrease until the solution becomes saturated and crystals form. Recrystallization can produce very pure compounds. The choice of recrystallization solvent is critical. A good recrystallization solvent will not dissolve the solid compound at low temperatures, but will dissolve it at high temperatures. The cold solvent also needs to dissolve the impurities. A typical recrystallization procedure involves dissolving the impure solid in a minimal amount of boiling solvent, followed by a cooling period. If insoluble impurities are found in the sample during heating, additional steps (hot-gravity filtration) are taken to remove them before cooling. After the hot solution cools and reaches the saturation point, small seed crystals of the compound will form in the solution. Slowly, additional molecules of the compound attach to the seed crystal and the crystals grow. Since molecules in the crystals typically have a greater affinity for other molecules of the same type than they do for any impurities, the process of crystal formation gives rise to relatively pure crystals. The impurities originally present in the compound are left in solution.

PROCEDURE :

• Take the compound in a watch glass and weigh it.

• Dissolve the given compound in 20-30 ml of water in a beaker. Stir it with the help of a glass rod . 

• Burn the burner and arrange the tripod stand and wire gauge. Now place the beaker on the heating set up and heat it until the compound dissolves.

• Place a filter paper in a funnel and filter the solution into a china dish.

• Allow the solution to cool down and wait until its water content evaporates.

• Now with the help of blotting paper absorb excess water and transfer the remaining content in a china dish and keep it aside.

OBSERVATION :

• Color of sample : White crystalline compound

• Yield of sample : 0.77g

RESULT :

• White color crystals are formed.

PRECAUTIONS :

• Filter the solution when it is hot.

• Use filter paper to hold the hot beaker and funnel.

• Wear lab coat and gloves.