Techniques for Separating Mixtures

Today we will be teaching you several techniques that are used to separate mixtures.
The result after the separation of the mixtures should be different components with different properties.

To do this, you must first realize how to differentiate between components and properties.
For instance, do you want materials to be separated by high density vs. low density, or do you want something reactive vs something inert?

The first method: Hand Separation (solids and solids)
This is the method to use if you want to separate mechanical mixtures or heterogeneous mixtures by using a magnet or some kind of sifting tool.

Second: Evaporation (solids dissolved in a liquid solution)
In this method, you would boil away the liquid, so only the solid would remain.


Third: Filtration (not dissolved solids and liquids)
First, you would pour the mixture containing solid particles through a porous filter.
The result should be solid particles staying on the filter and the liquid compounds passing through.


Fourth: Crystallization (solid in liquid)
Precipitation is the conversion of a solute to solid by chemical or physical change. First, the solids should be separated by filtration or floatation. Then, you need a supersaturated solution of the desired solid and cool it. The result should be pure crystals.


Fifth: Gravity Separation (solids based on density)
In this method, you would use a machine called a centrifuge. This machine would whirl the test tube around at very high speeds, causing the denser materials to move to the bottom.


Sixth: Solvent Extraction 
Here, the component moves into a solvent shaken with the mixture.
In a mechanical mixture (a solid with a solid), use a liquid to dissolve one solid, but not the other. This would result in the desired solid becoming left behind.
In a solution, the solvent is insoluble with the solvent that is already present. This solvent dissolves 1 or more substances, leaving the unwanted substances behind.

Seventh: Distillation (liquids in liquids) 
If you heat the mixture, the liquid with the lowest boiling point will vaporize first. Then, the vapour moves into the distillation flask and enters the condenser. As the gas cools, it condenses into a liquid, dropping the distillate as a purified liquid.


Eighth: Chromatography
In this method, you move a mixture over material that will retain some components more than others.
The components are distributed between 2 phases. A mixture dissolves in a mobile phase through a stationary phase.
This method can be used to separate very complex mixtures, such as plastics, drugs, and foods; it will also produce highly accurate analyses. There are 2 types of chromatography:

Paper Chromatography:
The stationary phase is a liquid soaked onto a strip of paper.
The mobile phase is the liquid solvent.
Some components tend to spend more time in the stationary phase than others. On the strip of paper, the components should appear as separate spots after drying or developing.


Thin Layer Chromatography:
The stationary phase is a thin layer of absorbent coating a sheet of plastic or gas.
Some of the components will attract to the absorbent strongly. As a result, the components will appear as spots on the sheet.


Here's a video on chromatography:


For more information on separation methods:
http://www.docbrown.info/page01/ElCpdMix/EleCmdMix2.htm