Thallium was discovered spectroscopically in 1861 by William Crookes (1832-1919) who isolated it by its green line. It is a rare soft white metallic element, occurring naturally in zinc blende and some iron ores. The book is an article written by the Fench chemist C A Lamy, who independently also isolated Thallium, leading to a scientific controversy over who discovered the element first. The specimens are Crookes' and contain a sample of Thallium as well as five of its compounds.
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