Caesium is the chemical element with atomic number 55. A soft,
silvery-gold alkali metal with a melting point of 28 °C (83 °F), it is
one of only five metals that are liquid at or near room temperature. It
has physical and chemical properties similar to those of rubidium and
potassium. The metal is extremely reactive and pyrophoric, reacting
with water even at −116 °C (−177 °F). It is the least electronegative
element with stable isotopes, of which it has only one, caesium-133.
Caesium is mined mostly from pollucite, while the radioisotopes,
especially caesium-137, are extracted from waste produced by nuclear
reactors. German chemists Robert Bunsen and Gustav Kirchhoff discovered
caesium in 1860 by flame spectroscopy. The first small-scale
applications for caesium have been as a "getter" in vacuum tubes and in
photoelectric cells. In 1967, a specific frequency from the emission
spectrum of caesium-133 was chosen for use in the definition of the
second by the International System of Units. Since then, caesium has
been widely used in atomic clocks. Since the 1990s, the largest
application of the element has been as caesium formate for drilling
fluids. It has a range of applications in the production of
electricity, in electronics, and in chemistry. The radioisotope
caesium-137 is used in medical applications, industrial gauges, and
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Today's selected anniversaries:
El Pueblo de San José de Guadalupe, the first civil settlement in the
Spanish colony of Alta California, was founded as a farming community.
The crew of the overcrowded British slave ship Zong killed 133 African
slaves by dumping them into the sea in order to claim insurance.
The Diet of Japan (pictured in session), a bicameral legislature
modelled after both the German Reichstag and the British Westminster
system, first met after the Meiji Constitution went into effect.
FC Barcelona, one of the most successful clubs in Spanish football, was
founded by Swiss football pioneer Joan Gamper.
The United Nations General Assembly voted to approve the Partition Plan
for Palestine, a plan to resolve the Arab–Israeli conflict in the
British Mandate of Palestine by separating the territory into Jewish
and Arab states.
Wiktionary's word of the day:
1. To lose strength and become weak; to be in a state of weakness or
2. To pine away in longing for something; to have low spirits,
especially from love
Wikiquote quote of the day:
Far away in the sunshine are my highest aspirations. I may not reach
them, but I can look up and see their beauty, believe in them, and try
to follow where they lead.
--Louisa May Alcott
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