Colourful metals

In 1859 Gustav Kirchhoff and Robert Bunsen invented a method for detecting the light spectra that substances produce when heated. They used the gas burner that Bunsen had invented, whose flame is very hot with little luminescence. This led to the discovery of elements whose names reflected the colour of the resultant light:

• Caesium—(discovered by Kirchhoff and Bunsen in 1860) from the Latin caesius, grey-blue, usually referring to the eyes

• Rubidium—(Kirchhoff and Bunsen, 1861) from Latin rubidus, red, describing a facial flush

• Thallium—(William Crookes, 1861) from Greek thallos, a young olive green shoot

• Indium—(Ferdinand Reich and Hieronymus Richter, 1863) from Greek indikon, indigo.

Chlorine gas is green (Greek chloros), and iodine vapour is violet (Greek ion). Platinum …