| Aim | a) Separation of pigments from extracts of leaves and flowers by paper chromatography and determination of Rf values. b) Separation of constituents present in an inorganic mixture containing two cations only (constituents having large difference in Rf values to be provided). |
| Apparatus Required | For Experiment (a) Filter paper Leaves and flowers Mortar and pestle Acetone Petroleum ether Pencil Beaker Developing chamber UV lamp For Experiment (b) Filter paper Inorganic mixture containing two cations only Pencil Beaker Developing chamber UV lamp |
| Theory | Paper chromatography is a technique used to separate and identify the components in a mixture. In this experiment, pigments from extracts of leaves and flowers will be separated using paper chromatography. The relative migration distance or Rf value of each pigment can be determined. Paper chromatography can also be used to separate inorganic compounds based on their chemical properties. In this experiment, an inorganic mixture containing two cations only will be separated using paper chromatography. The constituents having a large difference in Rf values will be provided. |
| Procedure | Procedure for experiment (a) Grind the leaves and flowers with a mortar and pestle. Add acetone to the ground leaves and flowers to extract the pigments. Filter the extract using filter paper. Mix the extract with petroleum ether in a beaker. Cut a strip of filter paper and draw a line using a pencil 1 cm from the bottom of the paper. Spot the pigment extract mixture on the line using a capillary tube. Place the filter paper in a developing chamber with a small amount of petroleum ether in the bottom of the chamber. Allow the solvent to travel up the paper. Remove the filter paper and let it dry. Determine the Rf value for each pigment spot using the formula: Rf = Distance traveled by the spot ÷ Distance traveled by the solvent front Procedure for experiment (b) Cut a strip of filter paper and draw a line using a pencil 1 cm from the bottom of the paper. Spot the inorganic mixture on the line using a capillary tube. Place the filter paper in a developing chamber with a small amount of solvent in the bottom of the chamber. Allow the solvent to travel up the paper. Remove the filter paper and let it dry. Determine the Rf value for each constituent using the formula: Rf = Distance traveled by the spot ÷ Distance traveled by the solvent front |
| Observation and Result | Observation: Different pigments present in the leaf and flower extracts will be separated on the paper, and their Rf values can be calculated. Result: The Rf values of each pigment can be used to identify the pigments present in the leaf and flower extracts. Observation: The constituents present in the inorganic mixture will be separated on the paper, and their Rf values can be calculated. Result: The Rf values of each constituent can be used to identify the constituents present in the inorganic mixture. The constituent with a higher Rf value traveled further up the paper, indicating that it is less polar or more soluble in the solvent. The constituent with a lower Rf value stayed closer to the starting line, indicating that it is more polar or less soluble in the solvent. |