Read our standard health & safety guidance
Refer to CLEAPSS Laboratory Handbook, Section 13.1
Carbon dioxide puts out a lighted splint and turns limewater milky; see also Preparing solutions and other reagents.
Hydrogen gives a ‘squeaky’ pop with a lighted splint.
Oxygen relights a glowing splint.
Chlorine a piece of damp blue litmus paper will be bleached white.
Students must be shown how to smell gases safely. They should be shown the technique with safe substances (e.g. carbon dioxide, ethyl ethanoate, dilute ammonia solution).
Test-tubes should be held about 30 cm from the face, level with the nose but pointing away. The vapour can then be gently wafted towards the nose with the other hand.
Alternatively, a deep breath can be taken and then attempts made to smell the gas. Only a little gas is inhaled but the smell can be detected.
Vapours must never be inhaled deeply and students known to have breathing difficulties (e.g. asthmatics), should not be asked to smell any chemical.
Health and safety checked, November 2007
Updated 3 Dec 2007
