FUNDAMENTAL PHOTOS / SCIENCE PHOTO LIBRARY FUNDAMENTAL PHOTOS / SCIENCE PHOTO LIBRARY
A paper chromatogram of a red dye used as a food colouring agent. The dye has been separated into its components, a light red and cyan. Paper chromatography involves placing a small amount of the substance under investigation on a piece of filter paper, then suspending one edge of the paper in a solvent, normally water. The solvent then passes up the paper by capilliary action, carrying with it the components of the substance at differing rates. The distance travelled along the paper during the time of the experiment is a measure of this transport rate.
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