GIPHOTOSTOCK / SCIENCE PHOTO LIBRARY GIPHOTOSTOCK / SCIENCE PHOTO LIBRARY
Paper chromatography, 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 graphite pencil is used to draw a line on a piece of filter paper. Several washable markers are used to put coloured dots on the line (orange, green, blue, black). The paper is then dipped in a 5% vinegar solution in a Petri dish, with the solution level below the dots. Capillary forces draw the solution up through the paper. The inks dissolve and travel up with vinegar, in the process separating into constituent pigments.
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