William Crookes
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Sir William Crookes was an English chemist and physicist who attended the Royal College of Chemistry, now part of Imperial College London, and worked on spectroscopy. He was a pioneer of vacuum tubes,
Crookes in 1906
Blue plaque, 7 Kensington Park Gardens, London
The element thallium, discovered by Crookes
The mineral crookesite, a selenide of copper, thallium and silver (Cu 7(Tl, Ag)Se 4), named for Crookes
Thallium
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Thallium is a chemical element; it has symbol Tl and atomic number 81. It is a silvery-white post-transition metal that is not found free in nature. When isolated, thallium resembles tin, but discolor
Crystals of hutchinsonite ((Tl,Pb)2As5S9)
A corroded thallium rod