GIPHOTOSTOCK / SCIENCE PHOTO LIBRARY GIPHOTOSTOCK / SCIENCE PHOTO LIBRARY
Chromatography flower, 3 of 3. Paper chromatography is a physical method for separation of mixtures. It is often used as a teaching tool to demonstrate separation of coloured inks and dyes. In this sequence a piece of filter paper folded in a cone is placed in a beaker with a 5% vinegar solution, such that the top of the cone is slightly above the rim. Several coloured washable markers are used to draw some lines around the centre of another piece of filter paper. This piece is then placed on top of the beaker. Capillary forces draw the vinegar up through the paper cone. When vinegar reaches coloured paper, it starts to spread from the centre to the periphery. The inks dissolve and travel with vinegar, in the process separating into constituent pigments.
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