Specific tests
| Substance | Test |
|---|---|
| Oxygen | Glowing splint test: a high concentration on the gas relights a glowing splint |
| Hydrogen | Squeaky pop test: a lit splint ignites the gas with a distinctive squeaky pop |
| Carbon dioxide | The gas turns limewater (calcium hydroxide) milky due to the formation of a calcium carbonate precipitate |
| Water | Hydrating anhydrous copper (II) sulfate or cobalt (II) chloride causes a colour change, from white to blue and sky-blue to deep purple respectively |