Rubidium, cesium and their compounds play an important role in both traditional and high-tech fields. In particular, rubidium and cesium are used as frequency standards for radio-frequency telecommunications, as the reference crystal oscillator in many atomic clocks and watches and in some lasers.
Rubidium sulfide (RuS) is an inorganic compound and salt with the chemical formula Rb2S. Like the other alkali metal sulfides, it has a cubic crystal structure. It is a colorless solid, and it is moderately water and acid soluble.
Its chemistry is similar to that of rubidium hydroxide, and its formation can be accomplished by treating rubidium with hydrogen sulfide gas under pressure. It is a reversible process, and the hydrogen sulfide gas can be recovered by distillation or filtration.
A significant quantity of the rubidium in the United States is produced by extracting it from the lithium and cesium brine that occurs naturally in the Great Basin of Nevada. However, the supply of natural rubidium has been limited by low demand. A number of methods are under investigation to improve the extraction process and to develop more efficient, economical and environmentally friendly production processes.
Rubidium is also an active ingredient in some medical equipment, such as positron emission tomographic imaging for the detection of epilepsy, and it is used in the electrostatic separation of nucleic acids and viruses. In telecommunications, rubidium is used in clocks and radiofrequency oscillators for precision timekeeping, signal transmission and synchronization. It is also used in night-vision devices and photomultiplier tubes.