GIPHOTOSTOCK / SCIENCE PHOTO LIBRARY GIPHOTOSTOCK / SCIENCE PHOTO LIBRARY
Paper chromatography, 1 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 graphite pencil is used to draw a line on a piece of filter paper. On top of it, a green line is drawn with a washable marker. The paper is then dipped in a 5% vinegar solution in a beaker, with the solution level below the line. Capillary forces draw the solution up through the paper. The ink dissolves and travels up with vinegar, in the process separating into constituent pigments.
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