Chemistry practical

Paper chromatography of food colourings

Run a food colouring beside four known dyes, measure each spot and the solvent front, calculate Rf values and identify the dyes in the mixture.

What you will do

1. 01Draw a baseline in pencil near the bottom of the paper.
2. 02Put a small spot of the mixture M and of each known dye A to D on the baseline.
3. 03Stand the paper in the solvent, with the baseline above the solvent, and put the lid on.
4. 04Take the paper out before the solvent reaches the top, and mark the solvent front straight away.
5. 05Measure how far each spot and the solvent front moved from the baseline, and calculate each Rf.