What is the flame colour of rubidium?

Rubidium is a soft, silvery-white metallic element of the alkali metals group (Group 1). It is one of the most electropositive and alkaline elements.

Rubidium can be liquid at ambient temperature, but only on a hot day given that its melting point is about 40°C. It ignites spontaneously in air and reacts violently with water and even with ice at -100 C, setting fire to the liberated hydrogen. As so with all the other alkali metals, it forms amalgams with mercury. It alloys with gold, cesium, sodium, and potassium. Its flame is yellowish-violet.

Applications

Rubidium and its salts have few commercial uses. The metal is used in the manufacture of photocells and in the removal of residual gases from vacuum tubes. Rubidium salts are used in glasses and ceramics and in fireworks to give them a purple colour. Potential uses are in ion engines for space vehicles, as working fluid in vapor turbines, and as getter in vacuum tubes.

Rubidium in the environment

Rubidium is considered to be the 16th most abundant element in the earth's crust. The relative abundance of rubidium has been reassessed in recent years and it is now suspected of being more plentiful than previously calculated. It is very like potassium and there are no environments where it is seen as a threat.

No minerals of rubidium are known, but rubidium is present in significant amounts in other minerals such as lepodite (1.5%), pollucite and carnallite. It is also present in traces in trace amounts in other minerals such as zinnwaldite and leucite.

The amount of rubidium produced every year is small, and what demand there is can be met from a stock of a mixed carbonate by-product that is collected during the extractium of litium from lepodite.

The little rubidium that is produced is used for research purposes only, these is no incentive to seek commercial outlets for the material.