JERRY MASON / SCIENCE PHOTO LIBRARY JERRY MASON / SCIENCE PHOTO LIBRARY
Performing a flame test (orange) on chalk. A flame test is a simple way to test for the presence of certain metals in a compound, in this case calcium. A small amount of the sample is held in a Bunsen flame. Some metals can be detected by the colour of flame produced. The colour of the flame is caused by the fluorescence of the metal ions within it; the compound is ionised by the heat and the excited metal ions give out light of a characteristic wavelength or colour. Chalk, a form of calcium carbonate, gives a characteristic dull orange flame. Smaller samples are held on a platinum wire as it does not give a flame test colour of its own.
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