Notes

Introduction

The word chromatography is derived from the Greek words meaning color (chroma) and writing (grapheim). Discovered by Russian scientist Michael Tswet in 1903 to describe his technique in deriving pigments in green leaves. Paper chromatography is a specific form of adsorption chromatography, where the paper acts as an adsorbent and separated through a solvent that allows the components in the mixture to flow through the paper. The differences in adsorbtion strength will result in variations in pigment and movement along the adsorbent. The more polar and the more ionic binding sites dye molecules have, the lower rate of flow. Rate of flow, or Rf, is the overall distance the solvent travels along the paper.
The purpose of this lab is to observe the different pigmentations seen during the passing of a mixture through it. The different colors observed will can be measured, finding rate of flow, which allows us to calculate polarity in the different pigmentations seen through the rate of flow. A lower Rf value shows that the dye is more polar than a dye with a high Rf.