Paper+Chromatography

=__**Paper chromatography**__= Paper chromatography is a technique of separating a mixture into its components depending on differences in solubilities in a particular solvent. =__Uses:__=

(a) Separate and determine the no. of components in a sample. (b) To identify both coloured and colourless components in a sample. (c) To determine the purity of a sample.

=__**How it works**__=

In the ascending method, the bottom edge of the paper is in contact with the solvent and is drawn upwards by capillary action.

In the descending method, the paper hands down from a solvent trough. The spots are applied just beneath the solvent level and are darawn downward by capillary action and gravity.

=__Retention factor__=

//Rf// value is a measure of the relative distance travelled by a component with respect to the solvent.

It is a ratio defined by : Rf = distance moved by the spot of the substance / distance moved by the solvent front

Rf is fixed for a particualr component given a particualr solvent, termperature conditions and chromatography paper.

It is to determine how far the substance moved in the solvent.

=__Locating Agent__=

Locating agent is a substance/liquid that help to separate and analyze colorless substances in chromatography by reacting with the colorless substance to form colored spots on the chromatogram.