7 - Identifying Ions

• What is the method for this practical?

  1. Pour 1cm3 of each known chloride solution into 5 test tubes.
  2. Clean the wire by dipping it in dilute hydrochloric acid.
  3. Dip the wire into the solution and hold the tip in a blue bunsen flame.
  4. Record the colour of the flame.
  5. Repeat for the following solutions and make sure to clean the wire after each test.
• How do you carry out a flame test to identify metal ions?

  Clean a wire loop by dipping it in HCl and then holding it in the blue flame until it burns without any colour. Dip the loop into the sample you want to test and put it into the blue flame of the Bunsen burner and record the colour of the flame.
• Precautions to take when using a Bunsen burner:

  • Don’t leave unattended
  • Turn off gas or leave on orange safety flame when not in use
  • Tie back long hair
  • Keep flammable chemicals away from the flame
• Why must the wire be cleaned before a flame test?

  To remove unwanted ions that may obscure the colour of the flame.