The Rf value is used to compare how far different substances travel along the chromatogram, allowing us to identify them based on their distances from the starting point.
Rf Formula
Required Practical- Chromatography
Required Practical- Chromatography
Use a pencil to draw a horizontal line near the bottom of the chromatography paper.
Place samples of known food colourings (A-D) next to an unknown substance (X) on the ‘start line’.
Place the paper in a beaker containing a small volume of solvent.
Let the solvent move to a few cm below the end of the paper.
By comparing spots produced by X with those produced by A-D, you will be able to identify the unknown substance.