Azeotropic Distillation
1. These are the mixture of liquids that cannot be separated by fractional distillation.
2. The mixtures that can be purified only by azeotropic distillation are called as azeotropes.
3. These azeotropes are constant boiling mixtures, which distil as a single component at a fixed temperature. For example ethanol and water in the ratio (95:5)
4. In this method the presence of a third component like C6H6, CCl4, ether, glycerol, glycol which act as a dehydrating agent depress the partial pressure of one component of azeotropic mixture and raises the boiling point of that component and thus other component will distil over.
Differential extraction:
1. The process of removing a substance from its aqueous solution by shaking with a suitable organic solvent is termed extraction.
2. When an organic substance present as solution in water can be recovered from the solution by means of a separating funnel.
3. The aqueous solution is taken in a separating funnel with little quantity of ether or chloroform (CHCl3).
4. The organic solvent immiscible with water will form a separate layer and the contents are shaken gently.
5. The solute being more soluble in the organic solvent is transfered to it.
6. The solvent layer is then separated by opening the tap of the separating funnel, and the substance is recovered.
Chromatography:
1. The principle behind chromatography is selective distribution of the mixture of organic substances between two phases – a stationary phase and a moving phase.
2. The stationary phase can be a solid or liquid, while the moving phase is a liquid or a gas.
3. If the stationary phase is solid, the basis is adsorption, and when it is a liquid, the basis is partition.
4. So the Chromatography is defined as a technique for the separation of a mixture brought about by differential movement of the individual compound through porous medium under the influence of moving solvent.
5. The various methods of chromatography are
· Column chromatography (CC)
· Thin layer chromatography (TLC)
· Paper chromatography (PC)
Adsorption chromatography:
1. The principle involved is different compounds are adsorbed on an adsorbent to different degree.
2. Silica gel and alumina are the commonly used adsorbent.
3. The components of the mixture move by varying distances over the stationary phase.
4. Column chromatography and thin layer chromatography are the techniques based on the principle of differential adsorption.
Partition chromatography:
1. Paper chromatography (PC) is an example of partition chromatography.
2. The same procedure is followed as in thin layer chromatography except that a strip of paper acts as an adsorbent.
3. This method involves continues differential portioning of components of a mixture between stationary and mobile phase.
4. In paper chromatography, a special quality paper known as chromatography paper is used. This paper act as a stationary phase.