Synthesis and separation.
Purification methods.
Recrystallisation is a purification technique used to separate a solid compound from impurities by exploiting differences in solubility.
How it works
- Dissolve the impure solid in a hot solvent in which the desired compound is highly soluble at high temperature but poorly soluble at low temperature.
- Filter hot, if needed, to remove insoluble impurities.
- Cool the solution, causing the desired compound to crystallize out while soluble impurities remain in solution.
- Collect the crystals by filtration and dry them.
Purpose
- To obtain a pure solid from an impure sample.
- Commonly used in organic and inorganic laboratories to purify synthesized products.
In this video Professor Dave explains in some detail how to use this method and why it works.