Crystallisation: This technique is used to separate two compounds with different solubilities in a solvent. The principle involves separating compounds based on their varying solubilities in a given solvent.

Distillation: This method is used to separate volatile liquids from nonvolatile impurities and liquids having sufficient difference in their boiling points. Liquids having different boiling points vaporise at different temperatures. The vapours are cooled and the liquids so formed are collected separately.

Example: Chloroform (b.p. 334 K) and aniline (b.p. 457 K) are easily separated by distillation. The liquid mixture is heated carefully, vapours of the lower boiling component form first, are condensed using a condenser, and collected. The higher boiling component forms later and is collected separately.

Chromatography: Based on the principle involved, chromatography is classified into adsorption and partition chromatography. Adsorption chromatography is based on the fact that different compounds are adsorbed on an adsorbent to different degrees.

Commonly used adsorbents are silica gel and alumina. When a mobile phase is allowed to move over a stationary phase (adsorbent), the components of the mixture move by varying distances over the stationary phase. Example: Column chromatography and thin layer chromatography are based on this principle of differential adsorption.