However, rubidium ions have the same charge as potassium ions, and are actively taken up and treated by animal cells in similar ways.
It is the second most electropositive of the stable alkali metals and melts at a temperature of 39.3 °C (102.7 °F).
Therefore, the less-soluble rubidium hexachloroplatinate (Rb Bunsen and Kirchhoff began their first large-scale isolation of caesium and rubidium compounds with 44,000 litres (12,000 US gal) of mineral water, which yielded 7.3 grams of caesium chloride and 9.2 grams of rubidium chloride.
They tried to generate elemental rubidium by electrolysis of molten rubidium chloride, but instead of a metal, they obtained a blue homogeneous substance which "neither under the naked eye nor under the microscope showed the slightest trace of metallic substance." They presumed it was a subchloride ( In a second attempt to produce metallic rubidium, Bunsen was able to reduce rubidium by heating charred rubidium tartrate.
Rubidium has also been reported to ignite spontaneously in air.
Rubidium chloride (Rb Cl) is probably the most used rubidium compound: among several other chlorides, it is used to induce living cells to take up DNA; it is also used as a biomarker, because in nature, it is found only in small quantities in living organisms and when present, replaces potassium.
Rubidium metal is easily vaporized and has a convenient spectral absorption range, making it a frequent target for laser manipulation of atoms.
Although rubidium is more abundant in Earth's crust than caesium, the limited applications and the lack of a mineral rich in rubidium limits the production of rubidium compounds to 2 to 4 tonnes per year.Because rubidium substitutes for potassium in the crystallization of magma, the enrichment is far less effective than that of caesium.Zone pegmatite ore bodies containing mineable quantities of caesium as pollucite or the lithium minerals lepidolite are also a source for rubidium as a by-product.Elemental rubidium is highly reactive, with properties similar to those of other alkali metals, including rapid oxidation in air.On Earth, natural rubidium comprises two isotopes: 72% is the stable isotope, Rb, with a half-life of 49 billion years—more than three times longer than the estimated age of the universe.Other common rubidium compounds are the corrosive rubidium hydroxide (Rb OH), the starting material for most rubidium-based chemical processes; rubidium carbonate (Rb Sr.