Element Thallium, Tl, Poor Metal
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Thallium History
In 1861 Sir William Crookes, an English chemist, had been examining the residues from a sulfuric acid plant, which were expected to contain selenium and tellurium. Selenium was actually found, but tellurium had not been chemically traced. However, examining the residues with a spectroscope, the most accurate analytical method of that time, Crookes discovered a beautiful green line that he had never previously seen. He concluded that the residues must contain a new element. Crookes named it Thallium, after the Greek thallos, green shoot or twig, the color of the vegetation in spring.
Thallium Occurrence
Poor metal Thallium crustal abundance is 7x10-5 mass %, which is hundredfold of gold abundance and tenfold of that of silver. Thallium is a trace element; its own minerals are very rare, but it vastly occurs as isomorphic component in a great number of other minerals, replacing copper, arsenic and silver in sulphide ores as well as potassium, rubidium and, less frequently, other alkali metals, in alumosilicates and chlorides.
Thallium is very abundant in leucite KAlSi2O6 and in orthoclase KAlSi3O8. It's content in lepidolite K2Li1.5Al1.5[Si3AlO10][F, OH]2 and in zinnwaldite is approximately 10-3-10-1%. Relatively large amount of thallium is found in pollucite: 10-2%. Thallium concentration in sulphide minerals is around 10-3%. This element has been found in deposits of zinc blende (sphalerite), and galena (lead glance). In hydrothermal sulphide, complex and lead-zinc ores the concentration may excess 0.1%.
The average abundance is 10-5% in soils, 10-9% in sea water, and 4x10-5% in animal tissues. Some plants such as beet, grapes, oak tree, beech tree as well as sea creatures and seaweed can extract environmental thallium and accumulate it. That is the reason of high thallium concentration in coals: 10-3-10-2%.
Thallium Neighbours
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