1860,1882 Caesium

The book of science

Tom Sharp

HeidelbergRobert Bunsen, Gustav Kirchhoff, Carl Setterberg elements Caesium


Robert Bunsen and Gustav Kirchhoff built a flame emission spectroscope in 1859 and in 1860 discovered caesium, the first element discovered by spectroscope. The spectrographic analysis of mineral water presented two bright lines for caesium so they named it after the Latin word for the color of its lines, “deep blue.” After distilling forty tons of this water, they obtained seventeen grams of caesium oxide. In 1882, one of Bunsen’s students, Carl Setterberg, got pure caesium from electrolysis of caesium cyanide.

Atomic number 55

Caesium formate for drilling fluids. Caesium atom transitions in atomic clocks. Caesium vapor to generate electricity from heat, to neutralize the space charge in vacuum tubes, and to emit light in magnetometers. Caesium in photoelectric cells. Caesium iodide and bromide in radiation detectors. Caesium nitrate in infrared flares.


Radioactive caesium-137, seven-eighths gone in a lifetime, produced in nuclear power plants by decay of uranium to xenon to caesium, and we used to think we would live, it seemed, forever.

Common isotopes of caesium are neither radioactive nor particularly toxic; however, the metal explodes violently on contact with water, even exposed to air with the slightest humidity.

See also in The book of science:

Readings on wikipedia:

Other readings:

  • Caesium,” Elementymology & Elements Multidict, by Peter van der Krogt