Colorless crystals or white powder; monoclinic structure; very hygroscopic; melts at 837°C; decomposes above 900°C; very soluble in water.
Rubidium carbonate is used in special glass and in fiber optics. It enhances stability and durability of glass, reducing its conductivity. It also is used in the preparation of Rb metal and other rubidium salts.
Rubidium carbonate is an intermediate in recovery of rubidium from lepidolite. The mineral, on prolonged heating with concentrated sulfuric acid, converts to alums.
The mixed alum solution, on treatment with ammonia or potassium carbonate, forms carbonates of potassium, rubidium and cesium. Rubidium carbonate is separated from other alkali metal carbonates by fractional crystallization (see Rubidium)
The carbonate salt also may be obtained by passing carbon dioxide through a solution of rubidium hydroxide in a fluorocarbon or nickel container. The solution is evaporated to yield the product carbonate.
Also, the salt may be prepared by adding ammonium carbonate to a solution of rubidium hydroxide. The solution is evaporated to dryness to expel ammonia.