Chemistry Required Practical: Chromatography


- The Method (In Blue)

- Common Mistakes (In Yellow)

- Safety Notes (In Pink)

  • Created by: Hannah
  • Created on: 26-03-19 11:39
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  • Chemistry Required Practical: Chromato-graphy
    • 1. Use a ruler to draw a horizontal pencil line 2 cm from a short edge of the chromato-graphy paper. Mark five pencil spots at equal intervals across the line. Keep at least 1 cm away from each end.
      • 2. Use a glass capillary tube to put a small spot of each of the known colourings on four of the pencil spots.  Then use the glass capillary tube to put a small spot of the unknown mixture on the 5th pencil spot. Try to make sure each spot is no more than 5 mm in diameter.   Label each spot in pencil.
        • 3. Pour water into the beaker to a depth of no more than 1 cm.
          • 4. Tape the edge of the chromatography paper to the glass rod. The paper needs to be taped at the end furthest from the spots. Rest the rod on the top edge of the beaker.  The bottom edge of the paper should dip into the water.
            • 5. Wait for the water solvent to travel at least three quarters of the way up the paper. Do not disturb the beaker during this time.  Carefully remove the paper. Draw another pencil line on the dry part of the paper as close to the wet edge as possible.
              • 6. Hang the paper up to dry thoroughly.
                • 7. Measure the distance in mm between the two pencil lines. This is the distance travelled by the water solvent.  Measure and record the same distance for each food colouring in the table below.
                  • 8. Use the following equation to calculate the Rf value for each of the known colours.
    • Try not to snap the capillary tube. They're made of thin glass.
    • Draw the line at the bottom of the paper in pencil. If its drawn with ink, it will run and ruin the chromato-gram.
      • Don't let the chromato-graphy paper touch the side of the beaker. If you do, it will distort the solvent front and make it harder to calculate an accurate Rf value.


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