Analysis of ions

6.1 Specific tests

6.3 Analysis of mixtures

Analysis of ions

  1. Flame tests

    1. Flame tests identify metal ions based on the colour they produce in a flame
    2. This is done by using a platinum of nichrome wire that has been cleaned by dipping it in concentrated hydrochloric acid then heating it in a Bunsen burner before moistening it in the acid so that a small amount of the salt being tested can stick to it and be held at the edge of the flame

    3. Colours of typical ions:

      Metal ions Flame colour
      Lithium Crimson
      Sodium Yellow
      Potassium Lilac
      Calcium Red
      Barium Green

  2. Reaction with sodium hydroxide

    1. Some metal ions, when reacted with sodium hydroxide, produce a precipitate:

      Metal ion Precipitate colour
      Calcium
      Magnesium
      Aliminium      		 White
      Copper (II) Blue
      Iron (II) Green
      Iron (III) Brown
    2. Aluminium hydroxide dissolves in excess sodium hydroxide

  3. Reaction with silver nitrate

    1. Halide ions, when reacted with silver nitrate solution in the presence of a catalyst of dilute nitric acid, produce a precipitate:

      Halide Precipitate colour
      Chloride White
      Bromide Cream
      Iodide Yellow

  4. Sulfate ions

    1. Sulfate ions, when reacted with barium chloride solution in the presence of a catalyst of dilute hydrochloric acid, produce a white precipitate