It then dries out, creating vast areas of tinder that can ignite spontaneously.

Found also to be chemically unstable, it was known to ignite spontaneously both in the laboratory and in a magazine.

Rubidium has also been reported to ignite spontaneously in air.

Sodium burns easily in air, and will ignite spontaneously on contact with water.

In fact the low-molecular weight compounds will ignite spontaneously on contact with air and are immediately destroyed by reaction with water molecules.