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For photoelectric cells.
(L. caesius, sky blue) Cesium was discovered spectroscopically by Bunsen and Kirchhoff
in 1860 in mineral water from Durkheim.
Cesium, an alkali metal, occurs in lepidolite, pollucte (a hydrated silicate of
aluminum and cesium), and in other sources. One of the world's richest sources of cesium
is located at Bernic Lake, Manitoba. The deposits are estimated to contain 300,000 tons of
pollucite, averaging 20% cesium.
It can be isolated by elecytrolysis of the fused cyanide and by a number of other
methods. Very pure, gas-free cesium can be prepared by thermal decomposition of cesium
The metal is characterized by a spectrum containing two bright lines in the blue along
with several others in the red, yellow, and green. It is silvery white, soft, and ductile.
It is the most electropositive and most alkaline element.
Cesium, gallium, and mercury are the only three metals that are liquid at
room temperature. Cesium reacts explosively with cold water, and reacts with ice at
temperatures above -116C. Cesium hydroxide, the strongest base known, attacks glass.
Because of it has great affinity for oxygen, the metal is used as a "getter"
in electron tubes. It is also used in photoelectric cells, as well as a catalyst in the
hydrogenation of certain organic compounds.
The metal has recently found application in ion propulsion systems. Cesium is used in
atomic clocks, which are accurate to 5 s in 300 years. Its chief compounds are the
chloride and the nitrate.
Cesium has more isotopes than any element--32--with masses ranging from 114 to 145.
The present price of cesium is about $30/g.
Sources: CRC Handbook of Chemistry
and Physics and the American Chemical Society.