- The noble metals (from silver upwards) do not combine directly with oxygen given as oxygen gas (02), although, like silver, they may absorb this gas largely when in the fused condition, and may not be proof against ozone, 03.

Upside down water filled burettes can be used to collect the oxygen gas.

The test for oxygen gas is that it relights a glowing splint.

If, instead of using copper electrodes, we take plates of platinum, copper is still deposited on the cathode; but, instead of the anode dissolving, free sulphuric acid appears in the neighbouring solution, and oxygen gas is evolved at the surface of the platinum plate.

Thus, with a dilute solution of sulphuric acid and platinum electrodes, hydrogen gas is evolved at the cathode, while, as the result of a secondary action on the anode, sulphuric acid is there re-formed, and oxygen gas evolved.