Testing for hydrogen
- Hold a burning splint at the open end of a test tube of the gas.
- Hydrogen burns rapidly with a squeaky pop.
Testing for oxygen
- Put a glowing splint into a test tube of the gas.
- The splint relights if oxygen is present.
Testing for carbon dioxide
- Shake the gas with, or bubble it through, limewater (calcium hydroxide solution).
- Limewater turns milky (cloudy) if carbon dioxide is present.
Testing for chlorine
- Hold damp litmus paper in the gas.
- Chlorine bleaches the litmus paper white. Blue litmus may turn red first, then white.
- Chlorine is toxic, so this test should be done in a fume cupboard.
Key terms
- Squeaky pop test
- The test for hydrogen: it burns with a squeaky pop.
- Glowing splint
- A splint with no flame that relights in oxygen.
- Limewater
- Calcium hydroxide solution, which turns milky with carbon dioxide.
- Litmus paper
- An indicator paper; damp litmus is bleached by chlorine.
- Bleach
- To remove colour, as chlorine does to damp litmus.
- Fume cupboard
- An enclosed space with an extractor fan, used for toxic gases.