Pyrite, 33 thallium

Thallium occurs in crooksite, lorandite, and hutchinsonite. It is also present in pyrites and is recovered from the roasting of this ore in connection with the production of sulfuric acid. It is also obtained from the smelting of lead and zinc ores. Extraction is somewhat complex and depends on the source of the thallium. Manganese nodules, found on the ocean floor, contain thallium. 

Crookesite. In 1866 Baron Nils Adolf Erik Nordenskiold found among the collections at the Royal Museum in Sweden a rare mineral from Skrikerum, which C. G. Mosander had regarded as a copper selenide. When Baron Nordenskiold analyzed it, he found it to be a selenide of copper, silver, and thallium. Because it was the first mineral of which the recently discovered element thallium was shown to be an essential constituent, he named it crookesite in honor of Sir William Crookes, the discoverer of thallium (31). Although crookesite is very rare, selenium and thallium are often found associated in nature, and both of these elements, so different in chemical properties, were originally discovered in the same source, namely the slime in the lead chambers of sulfuric acid plants using seleniferous and thalliferous pyrite. 

When burned in suitable pits, pyrite yields, among other products, sulfur dioxide, arseniouS and selenious adds, and the oxide of thallium, which are carried over into the first lead chamber, with the ferruginous dust. In this first chamber, espedally if it has no other communication with the following ones than the gas pipe, the oxide of thallium deposits and accumulates, and finally thallium sulfate, with sulfates of lead, iron, and other foreign substances coming fiom the pyrite. 

Thallium in Pyrite. In 1867 Dr. E. Carstanjen found that the flue dust from the pyrite-roasting kilns of L. Rohr s sulfuric acid plant at Oranienburg was unusually rich in thallium. It yielded on analysis 3.5 per cent of metallic thallium. By working up a large quantity of flue dust from several kilns, he prepared twenty or thirty pounds of the metal. 

In 1863 Reich began a search for thallium in some Freiberg zinc ores from the Himmelsfurst mine consisting mainly of arsenical pyrites, blende, lead glance, silica, manganese, copper, and small amounts of tin and cadmium (19, 43). After roasting the blende to remove most of the sulfur and arsenic, he decomposed it with hydrochloric acid (47). When Clemens Winkler, who was then a metallurgist in the Saxon smalt works, visited Professor Reich in 1863, the latter showed him a straw-yellow precipitate and said, This is the sulfide of a new element (52). Because of his colorblindness, however, Reich entrusted the spectroscopic examination to his assistant, Richter. 

Thallium occurs in small amounts in pyrite, zinc blende, and hematite of certain localities, and in a few rare minerals in Sweden and Macedonia. 

For the recoveiy of thallium from the flue dust of pyrite burners, the dust is boiled with H2O, allowed to stand some time, filtered, and HC1 added to die filtrate, whereupon crude thallous chloride is precipitated. This is purified by further treatment, and thallium metal obtained (1) by electrolysis of the sulfate solution or (2) by fusion of the chloride widi sodium cyanide and carbonate. 

The other elements are found only in trace quantities. Gallium and indium occur in aluminum and zinc ores, for example in bauxite, but the richest sources contain <1% of Ga and still less In. Thallium is widely distributed and is usually recovered from flue dusts from the roasting of pyrites. 

When pure the density of iron pyrites is 5 027 at 25° C.2 Nickel and cobalt are sometimes present, probably as isomorphous intermixtures of their corresponding sulphides copper may also be present, perhaps as chalcopynte. Thallium, silver, and even gold have been found in pyrites, the last-named in sufficient quantity to render the mineral a profitable source of that precious metal, as, for example, m British Columbia, where auriferous pyrites is largely worked. 

Thallium is manufactured commercially as a by-product from the roasting of pyrite ores, from sulfuric acid plants, and from the smelting of lead, zinc, and copper. The global... 

Thallium (10 % of earth s crust) is recovered principally from the flue dust of pyrites burners. The soft, grey metal, which has a hexagonal close-packed structure, is rather more reactive than gallium and indium because of the ease with which it forms a unipositive ion. It oxidises in moist air, decomposes steam at red heat and dissolves readily to form thallium(I) compounds in dilute mineral acids other than HCl, because of the insolubility of TlCl. 

Over a year after Crookes original discovery Lamy, in France, made a similar investigation of the lead chamber deposits of a sulfuric acid plant which used a Belgian pyrite. He found thallium in considerable quantities, and by May, 1862, he had a considerable amount of the metal in lump form. He studied the physical and chemical properties of the element and many of its compounds. 

Thallium is obtained from the dust deposited in the flues of the pyrites burners used in the manufacture of sulphuric acid. The separation of thallium from other metals depends on the fact that it is the only metal with a soluble carbonate and an insoluble chloride. It is a bluish-white metal, easily deformed and softer than lead, being present at concentrations of 0.6-0.7 ppm in the earth s crust, and although it can be found in pure metallic form it is more commonly associated in mineral combination. 

In April 1862, Claude August Lamy independently obsenved the same green line due to thallium in the spectrum obtained from slime from a sulphuric acid works at Loos, where Belgian pyrites were used. More fortunate than Crookes he had considerable quantities of material at his disposal and soon established the metallic nature of thallium. In May of the same year hq was able to display a lump of the metal and before the end of the year he isolated several hundred grams and gave a fairly complete account of the physical and chemical properties of the metal. ... 

Besides accidential or suicidal ingestion, there is occupational exposure of some groups of employees in the production and processing of heavy metal ores, manufacturing and use of thallium, its alloys and compounds, and in certain cement factories from roasting pyrites and ingestion of dust from the electric filter (Schaller et al., 1980). Whereas the excretion level in urine from persons without known occupational contact with thallium was found to be lower than 1.1 mg Tl/kg creatinine, it significantly increases upon exposure. No influence of the age of the person examined and the duration of employment, as well as no influence of alcohol and nicotine consumption was noted. 

Thallium occurs in nature in potash minerals and pyrites from which the metal is recovered. Thallium has a metallic luster when freshly cut, but upon exposure to air it forms a bluish-gray appearance that is similar to lead. It combines with several elements forming binary compounds. 

Most important mineral (Cu.TI.AgjjSe is a rare mineral, named crookesite, after Sir William Crookes. Thallium is however obtained as a by-product of zinc and lead production. The element is finely dispersed in feldspar and pyrite, as well as in zinc and lead ores. 

At the age of nearly 65, in the year 1863, he decided to search for the element thallium in the zinc ores of the Freiberg region. Thallium had been discovered in England two years earlier in residues collected in a lead chamber from sulfuric add manufacture. The sulfur (and thallium) originated from the mineral pyrite. The complex... 

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