Please enable JavaScript.
Coggle requires JavaScript to display documents.
Experimental Techniques (Methods of purification (Distillation (It is used…
Experimental Techniques
-
Criteria of Purity
Paper Chromatography
-
Rf Values
An Rf value indicates the solubility of a specific pigment. To find it divide the distance travelled by the solvent by the distance travelled by the component/pigment.
How to interpret
The pigments will be separated by the solvent, which carries each one up the paper to a certain point. Each pigment will leave a dot or line where it stops. If there is only one dot on the paper then the substance is pure. If there is more than one, it contains more than one pigment and is not pure.
-
Importance of purity
If there are impurities in foods and especially medical drugs there can be disastrous side effects. Having a bunch of different substances mixed together in an impure substance can cause reactions that shouldn't occur. This can make it dangerous to consume these products.
Methods of purification
Distillation
It is used to separate a liquid from a soluble solid. The solution is heated and the liquid turns into a gas and travels up the apparatus, then condensing in the condenser, leaving behind the soluble solid.
Crystilisation
It is used to obtain a crystal (usually a salt) from a solution. First the solution is heated to evaporate the solvent. Next the solution is left to cool and form crystals, if there is any excess liquid the crystals can be filtered out.
Fractional Distillation
It is used to separate a substance containing two or more miscible liquids using their differing boiling points. The solution is put into a flask and heated then it turns into gas and travels up a fractional distillation column at which they condense and are separated.
Paper Chromatography
It is used to separate soluble substances that are mixed together. It has two stages, the stationary phase - paper and the mobile phase - the solvent moving through the paper. The solvent moves the substances within the mixture and separates them so they can easily be separately identified.