FWS -Playing With Fire! (flame test)

A flame test used to identify boron and sodium.

Ethanol, Sodium chloride and boric acids flames

Boric acid flame

Ethanlo flame

Boric acid flame in the wind

Sodium chloride flame

Abstract

In this experiment, you will use a flame test to visually determine the identity of a metal or metalloid ion, based on the colour it turns a flame. This is because each element has an exactly-defined emission spectrum, which scientists can use to identify them. For example, lithium produces a red flame and sodium a yellow flame. This experiment can be performed at home, but must be done under the supervision of a responsible adult.

Materials and Equipment

• Safety equipment (fire extinguisher, fire blanket, etc)
• Ethanol
• The metal part of a tea light
• Disposable spatula of some sort
• Lighter
• Metal salt

Safety Procedures

• Have fire safety equipment standing by.
• Find a safe, open place outside to perform the experiment, away from anything flammable. Remember, if something were to go wrong, isolation is the best defence, as the experiment will soon run out of flue and the flame will be extinguished.
• Keep the ethanol contained and at least 5 metres away from the experiment at all times.
• Do not upscale the reaction and never use more than 1ml of ethanol for this experiment.
• Do not mix the salts together to try and make different colours.
• Use a new tea light for every experiment.
• Once the experiment is lit, stand back – the fumes are toxic.
• Do not return to the experiment until the flame has gone out.
• Remember that the tea lights will remain hot for some time after the flame has gone out

Experimental Procedure

• Remove the candle from the tea light, leaving the metal case.
• Place a small amount of the salt to be tested into the case. Remember, these salts can be toxic so handle with care.
• Add a small amount of ethanol (1ml) into the tea light so it just covers the salt and mix the two together thoroughly.
• Place the tea light at least 5 metres away from where you are going to stand, away from anything flammable. Light the ethanol and stand back.
• Observe the colour of the flame and do not return to the tea light until the flame has gone out.