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Cesium
The
metal is characterised by a spectrum containing two bright lines in the
blue (accounting for its name). It is silvery gold, 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 or
around room temperature. Cesium reacts explosively with cold water, and
reacts with ice at temperatures above -116°C. Cesium hydroxide is a
strong base and attacks glass.
Cesium reacts with the halogens to form a fluoride, chloride, bromide,
and iodide. Cesium metal oxidized rapidly when exposed to the air and
can form the dangerous superoxide on its surface.
Applications
Cesium is used in industry as a catalyst promoter, boosting the
performance of other metal oxides in the capacity and for the
hydrogenation of organic compounds. Cesium nitrate is used to make
optical glasses. Cesium is sometimes used to remove traces of oxygen
from the vacuum tubes and from light bulbs. Cesium salts are used to
strenght various types of glass. The chloride is used in photoelectric
cells, in optical instruments, and in increasing the sensitivity of
electron tubes. Cesium is used in atomic clocks and more recently in ion
propulsion systems.
Cesium in the environment
Although cesium is much less abundant than the other alkali metals,
it is still more common than elements like arsenic,
iodine and uranium. Few
cesium mineral are know, pollucite is the main: they are silicate magmas
cooled from granites.
World production of cesium compounds is just 20 tonnes per year, coming
mainly from the Bernic lake (Canada) with a little from Zimbabwe and
South-West Africa.
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Humans may be exposed to cesium by breathing,
drinking or eating. In air the levels of cesium are generally low,
but radioactive cesium has been detected at some level in surface
water and in many types of foods.
The amount of cesium in foods and drinks depends upon the emission
of radioactive cesium through nuclear power plants, mainly through
accidents. These accidents have not occurred since the Chernobyl
disaster in 1986. People that work in the nuclear power industry
may be exposed to higher levels of cesium, but many precautionary
measurements can be taken to prevent this.
It is not very likely that people experience health effects that
can be related to cesium itself. When contact with radioactive
cesium occurs, which is highly unlikely, a person can experience
cell damage due to radiation of the cesium particles. Due to this,
effects such as nausea, vomiting, diarrhoea and bleeding may
occur. When the exposure lasts a long time people may even lose
consciousness. Coma or even death may than follow. How serious the
effects are depends upon the resistance of individual persons and
the duration of exposure and the concentration a person is exposed
to.
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Cesium occurs naturally in the environment
mainly from erosion and weathering of rocks and minerals. It is
also released into the air, water and soil through mining and
milling of ores.
Radioactive isotopes of cesium may be released into the air by
nuclear power plants and during nuclear accidents and nuclear
weapons testing.
The radioactive isotopes can only be decreased in concentration
through radioactive decay. Non-radioactive cesium can either be
destroyed when it enters the environment or react with other
compounds into very specific molecules. Both radioactive and
stable cesium act the same way within the bodies of humans and
animals chemically.
Cesium in air can travel long distances before settling on earth.
In water and soils most cesium compounds are very water-soluble.
In soils, however, cesium does not rinse out into the groundwater.
It remains within the top layers of soils as it strongly bonds to
soil particles and as a result it is not readily available for
uptake through plant roots. Radioactive cesium does have a chance
of entering plants by falling on leaves.
Animals that are exposed to very high doses of cesium show changes
in behaviour, such as increased or decreased activity.
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periodic elements. |
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