- Cut the paper so that it doesn't reach to bottom of an empty beaker
- Fasten a piece of paper to a pencil or splint
- Draw a pencil line about 2cm from the bottom of the paper
- Drop a sample of each colouring on the pencil line and let it dry
- Label the samples on the paper using a pencil
- Put about 1cm depth of solvent into the beaker
- Put the paper into the beaker so that the end of it just dips into the solvent
- Leave the paper in the solvent until the solvent has nearly reached the top of the paper
- Remove the paper from the solvent and use a pencil to mark where the solvent ahs reached
- Allow the paper to dry, then measure the distance between your original pencil line and the line the solvent reached
- Measure the distance of each spot from the orignal pencil line
- Calculate the Rf value for each substance in the dyes by dividing the distance each substance has travelled by the distance the solvent has travelled
- Compare the Rf values of different substances to try to identify them
Rf = Distance moved by ink ÷ Distance moved by solvent
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