Required Practical 10a Steps

Outline Step 1 in Recrystallisation

Dissolve the impure compound in a minimum volume of hot solvent

Outline step 2 in recrystallisation

Hot filter solution through fluted filter paper quickly

Outline step 3 of recrystallisation

Cool the filtered solution by inserting the beaker in ice

Outline step 4 of recrystallisation

Suction filtrate with a Büchner flask to separate out crystals

Outline step 5 of recrystallisation

Wash the crystals with distilled water

Outline step 6 of recrystallisation

Dry the crystals between absorbent paper

What is the reason for step 1 of recrystallisation

An appropriate solvent is one which will dissolve both compound and impurities when hot and one in which the compound itself does not dissolve well when cold. The minimum volume is used to obtain saturated solution and to enable crystallization on cooling.

What is the reason for step two of recrystallization

This step will remove any insoluble impurities and heat will prevent crystals reforming during filtration

What is the reason for step 3 of recrystallization

Crystals will reform but soluble impurities will remain in solution form because they are present in small quantities so solution is not saturated. Ice will increase the yield of crystals.

What is the reason for step 4 of recrystalisation

The water pump connected to the Buchner flask reduces the pressure and speeds up the filteration

What is the reason for step 5 of recrystallisation

To remove soluble impurities