Colourful metals
Authors: Jeff Aronson
Journal: BMJ (2007)

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 shines like silver (Spanish plata), and orpiment (aurum pigmentum, arsenic trisulphide) gleams like gold; the Greek for orpiment was arsenikon (Hebrew zarnik). Gold (Arabic zarqun) also gives us zirconium, from the golden mineral zircon. Like chromium (Greek chroma, colour), rhodium (rhodon, a rose), and praseodymium (prasios, leek green, also vomitus), vanadium may get its name from its attractively coloured salts—Vanadis was the beautiful Norse goddess Freya or one of her attendants. One of the most colourful elements, iridium, is named after the rainbow (Greek iris), and pale bismuth (German Wismut) may mean “white mass.” 

When Alexander Litvinenko, a former KGB officer and an outspoken critic of Vladimir Putin, became ill while investigating the murder of the Russian journalist Anna Politkovskaya, thallium poisoning was suspected. The cardinal features are nausea, vomiting, diarrhoea, a painful ascending neuropathy, skin rashes, and alopecia. 

Agatha Christie described thallium poisoning in her novel The Pale Horse (Collins, 1961), and Dennis Sanders and Len Lovallo, in The Agatha Christie Companion (W H Allen, 1985), described three cases in which the diagnosis was made by people who had read the book and recognised the symptoms. In 1975 a woman wrote to Christie from a Latin American country, telling her that, having read The Pale Horse, she had saved the life of a man whose wife was poisoning him. In 1977 a London nurse, Marsha Maitland, diagnosed thallium poisoning in a 19 month old baby from Qatar. An earlier case is the best known. In 1971, workers at the Hadlands Photographic Equipment works in Bovingdon, Hampshire, developed illnesses thought to be infectious, attributed to the “Bovingdon bug”; some died. Dr Hugh Johnson, a forensic expert, remembering Christie's novel, suspected thallium poisoning and fingered Graham Frederick Young, who worked at Hadlands. Thallium and other poisons were found in his flat. After the jury found him guilty, it was revealed that he had not long before been released from Broadmoor, after serving nine years of a 15 year sentence for the attempted murders of his father, sister, and a friend; he probably also murdered his mother. 

In 1996 a Chinese girl called Zhu Ling developed an illness that was diagnosed first as Guillain-Barre syndrome and then as acute disseminated encephalomyelitis (BMJ 1996;312:318-9). When a friend sent a message on the internet asking for help many respondents suggested thallium poisoning, which was confirmed. 

In 2005 an unnamed Japanese girl was accused of poisoning her mother with thallium. She had read Anthony Holden's book, The St Albans Poisoner: The Life and Crimes of Graham Young (Hodder & Stoughton, 1974), had seen The Young Poisoner's Handbook (1995), a film based on Young's life, and had read The Pale Horse. 

However, thallium was not the green toxin that killed Litvinenko, but a red herring. The poison was polonium, which is another story.