Chemical tests

Test for sulfur dioxide

Sulfur dioxide turns acidified potassium dicromate (VI) solution from orange to green by reducing the chromium ions from +6 to +3

Test for Oxygen

Relights a glowing splint

Test for Hydrogen

With lit splint, squeaky pop

Test for Aldehydes

Tollen's silver mirror

Solution of silver nitrate and aqueous ammonia. When warmed, colourless silver ions are reduced to metallic silver

Fehling's solution

Contains blue copper ions when warmed, forms brick red precipitate

Tests for carboxylic acids

Add sodium hydrogen carbonate, carbon dioxide formed

Test for alkenes

Shake with bromine water, changes from orange-brown to colourless

Test for alcohols

Add acidified potassium dicromate (VI), changes from orange to green

Test for halagenoalkanes

Add aqueous sodium hydroxide, warm. acidify with nitric acid, add silver nitrate. a precipitate forms

Test for metal halides

Add dilute nitric acid, a few drops of silver nitrate.


White precipitate that dissolves in ammonia


Cream precipitate that dissolves in concentrated ammonia


Yellow precipitate insoluble in ammonia

Flame tests

Clean a nicrome wire by dipping it in hydrochloric acid and holding in a blue bunsen flame. Repeat unitill no colour is shown. When clean, dip again in the acid, and then into solid to be tested, place in the flame again. The colours shown should look a bit like the table below:

Colour Colour
Li crimson Cu blue-green
Na orange Ca orange-red
K lilac Sr red
Rb red Ba apple green
Cs blue Pb Light blue