Cesium is a rare metal. It’s used in a relatively small number of commercial applications; only about 55,000 pounds are used worldwide each year. The largest use of cesium is by the petroleum industry, where it’s used as a component of drilling mud. Cesium is used in the U.S. Naval Observatory’s atomic clocks and in ground systems used to track the space shuttle and satellites. Cesium is also used in agriculture and in the manufacture of certain electrical components. A radioactive isotope of cesium is used in treating cancer.

Cesium is the most reactive metal on earth. When exposed to air, cesium will ignite spontaneously. When exposed to water, cesium causes hydrogen gas to be released, which explodes immediately as a result of the heat created by the interaction between the water and cesium. Because of its volatility, cesium is classified as a hazardous material that requires special care in its storage and transport.

When in storage or in transport, cesium must not be allowed to come in contact with water, air, or even water vapor in the air. Cesium is often stored submerged in mineral oil or kerosene. These materials prevent cesium from contacting air and reacting explosively with oxygen and water vapor. Cesium is also sometimes stored in stainless steel containers that have been hermetically sealed after all air has been extracted. Cesium is also stored in vacuum-sealed glass ampoules. It can be sealed in containers with a dry, inert gas such as argon.

When shipping cesium, precautions must be taken to ensure that the metal does not come in contact with air. Cesium is often shipped in the same hermetically sealed stainless steel containers that it is stored in, as well as the vacuum-sealed glass ampules. When the ampules are shipped, they are usually wrapped in foil, and they are packed in a metal can along with an inert cushioning material such as vermiculite.