Summary GCSE Combined Science Chemistry - chromatography required practical

Chromatography required practical
A sample of unknown food colouring is a mixture of chemicals (labelled U), two known food
colourings it could contain are labelled A, B and C.

1 Use a pencil to draw a horizontal base line on the chromatography
paper, 2 cm from the bottom of the paper.
2 Mark 5 pencils marks at equal distance across the line, leaving
1cm space at the sides
3 Use a capillary tube to put a small spot of each of the known food
colours and the unknown colour onto the pencil marks and allow it
to dry.
4 Fold the top edge of the chromatography paper over a wooden
splint and keep in place with a paperclip.
5 Add 0.5 cm depth of water (the solvent) into the beaker.
6 Carefully put the chromatography paper into the beaker and leave
until the solvent front (farthest point reached by the solvent) is past
the last coloured spot.
7 Remove the chromatography paper. Using a pencil, mark the
solvent front and the coloured spots.
8 Allow the paper to dry.



+ - height of solvent


• •
,.• •
... ., ., ..
,, +- base line (in pencil)
A B C