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Flame Tests Tutorial

Key Concepts

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Performing a Flame Test

  1. Clean a platinum or nickel-chromium wire loop by dipping it into concentrated   acid (hydrochloric acid or nitric acid are often used).
  2. Rinse the acid washed wire loop with deionized water.
  3. Test the cleanliness of the wire loop by placing it into the flame of a bunsen burner.
  4. If the bunsen burner's flame changes colour, then the wire loop is not clean and you will need to repeat steps 1 to 3.
    If the bunsen burner's flame does not change colour, then the wire is clean and you can proceed to step 5.
  5. Dip the clean wire loop into the sample (powder or solution).
  6. Place the wire loop containing the sample into the blue part of the bunsen burner's flame.
  7. Observe the change in the colour of the bunsen burner's flame.
  8. To perform another test, repeat steps 1 to 7.

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Using Flame Tests

The element present in an unknown salt is identified by comparing the colour of the flame obtained during the flame test with the colour of the flames known to be produced by a range of elements.

The flame colours produced by a number of elements are given in the table below:

Flame tests are usually used to detect the presence of metals, but some semi-metals (metalloids) and non-metals (such as phosphorus) can also be detected.

There are a number of limitations of flame tests:

  • Flame tests cannot detect all elements.
    Some elements produce similar flame colours.
    Many elements produce no change in flame colour.
  • Flame tests cannot usually detect low concentrations.
  • Impurities can mask the flame colour.
    Sodium, with its intense yellow flame, is capable of masking the colour produced by other elements if it is present as an impurity.
    Sometimes, viewing the flame through blue glass can filter out the yellow of sodium's flame.
element flame colour
antimony pale green
arsenic blue
barium yellowish green
boron bright green
calcium orange to red
cesium blue
copper green or blue
indium blue
iron gold
lead blue
lithium pink to red
magnesium bright white
manganese(II) yellowish-green
molybdenum yellowish-green
phosphorus pale bluish-green
potassium lilac to violet
rubidium red to violet
selenium azure blue
sodium intense yellow
strontium crimson to red
tellurium pale green
thallium green
zinc bluish-green

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