Sources of the elements

In the eighteenth and nineteenth centuries, chemists had so successfully isolated the elements that John Dalton was able to put together a genuine atomic theory. Dmitri Mendeleyev organised the elements into his periodic table, the culmination of scientific elegance. 

physical chemistry has accomplished its great task of elucidating the microcosmos. The existence, properties and combinatory rules for atoms have been firmly established. The problem now is to work out where they came from. Their source clearly lies outside the Earth, for spontaneous (cold) fusion does not occur on our planet, whereas radioactive transmutation (breakup or decay), e.g. the decay of uranium to lead, is well known to nuclear geologists. The task of nuclear astrophysics is to determine where and how each species of atomic nucleus (or isotope) is produced beyond the confines of the Earth. 

This raises the burning question starting out from a simple substance (not to say elementary) made up of photons, electrons, neutrinos, neutrons and protons, what mechanisms exist for synthesising the many and varied nuclei to be found in nature This in turn raises the question where and when did these processes take place, and how do they fit together chronologically as the Universe has evolved  

Working with this quintet of particles, symbolically denoted y, e, v, n and p, nature built up all the elements in the periodic table, conferring their distinctive 

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Beryllium is found in some 30 mineral species, the most important of which are bertrandite, beryl, chrysoberyl, and phenacite. Aquamarine and emerald are precious forms of beryl. Beryl and bertrandite are the most important commercial sources of the element and its compounds. Most of the metal is now prepared by reducing beryllium fluoride with magnesium metal. Beryllium metal did not become readily available to industry until 1957. 

Never found free in nature, it is widely distributed in combination with minerals. Phosphate rock, which contains the mineral apatite, an impure tri-calcium phosphate, is an important source of the element. Large deposits are found in Russia, in Morocco, and in Florida, Tennessee, Utah, Idaho, and elsewhere. 

Commercial production from petroleum ash holds promise as an important source of the element. High-purity ductile vanadium can be obtained by reduction of vanadium trichloride with magnesium or with magnesium-sodium mixtures. 

Rubidium is found widely dispersed in potassium minerals and salt brines. LepidoHte [1317-64-2] a lithium mica having the composition KRbLi(0H,F)Al2Si20 Q, contains up to 3.5% Rb20 and is the principal source of the element. An ore that is basically poUucite [1308-53-8] ... 

The spectacular success (in 1807) of Humphry Davy, then aged 29 y, in isolating metallic potassium by electrolysis of molten caustic potash (KOH) is too well known to need repeating in detail." Globules of molten sodium were similarly prepared by him a few days later from molten caustic soda. Earlier experiments with aqueous solutions had been unsuccessful because of the great reactivity of these new elements. The names chosen by Davy reflect the sources of the elements. 

Tin occurs mainly as cassiterite, Sn02, and this has been the only important source of the element from earliest times. Julius Caesar recorded the presence of tin in Britain, and Cornwall remained the predominant supplier for European needs until the present century (apart from a minor flourish from Bohemia between 1400 and 1550). Today (1990s) world production approaches 200 000 tonnes per annum (see next section), of which the UK contributes less than... 

The commercial recovery of iodine on an industrial scale depends on the particular source of the element.Erom natural brines, such as those at Midland (Michigan) or in Russia or Japan, chlorine oxidation followed by air blowout as for bromine (above) is much used, the final purification being by resublimation. Alternatively the brine, after clarification, can be treated with just sufficient AgNOs to precipitate the Agl which is then treated with clean scrap iron or steel to form metallic Ag and a solution of EeU the Ag is redissolved in HNO3 for recycling and the solution is treated with CI2 to liberate the h ... 

Additional sources of the elements are tin slag and scrap. For instance, cassiterite deposits, in Australia, Brazil, Thailand and some other countries, contain a significant amount of tantalum. The bulk of this tantalum is collected in the slag and processed separately. Recycling of various tantalum-bearing scrap is also a veiy important source for tantalum production. These scrap materials include powder surplus from sintering operations, scrap from mill products, rejected and used capacitors, scrapped cutting tools and furnace hardware. 

Many of the metals used by ancient man— coppei (cuprum, Cu), silver (argentum, Ag), gold (aurum, Au), tin (stannum, Sn), and lead (plumbum, Pb)—are in relatively short supply. Ancient man found deposits of the first three occurring as the elementary metals. These three may also be separated from their ores by relatively simple chemical processes. On the othei hand, aluminum and titanium, though abundant, are much more difficult to prepare from their ores. Fluorine is more abundant in the earth than chlorine but chlorine and its compounds are much more common—they are easier to prepare and easier to handle. However, as the best sources of the elements now common to us become depleted, we will have to turn to the elements that are now little used. 

Boron, a metalloid with largely nonmetallic properties, has acidic oxides. Aluminum, its metallic neighbor, has amphoteric oxides (like its diagonal neighbor in Group 2, beryllium). The oxides of both elements are important in their own right, as sources of the elements, and as the starting point for the manufacture of other compounds. 

A summary is given in Table III of the results of the elucidation of the sources of the elements in remote atmospheric dusts. Four main sources are identified silicate o dust, marine spray, high temperature natural emissions (e.g. volcanic, plant and rock... 

Table VII. Sources of the Elements in Street Dust and House Dust...

More detailed statistical analyses (chemical element balance, principal component analysis and factor analysis) demonstrate that soil contributes >50% to street dust, iron materials, concrete/cement and tire wear contribute 5-7% each, with smaller contributions from salt spray, de-icing salt and motor vehicle emissions (5,93-100). A list is given in Table VII of the main sources of the elements which contribute to street dust. 

The stannane-thiones, -selenones, and -tellurones are usually prepared by addition of the element, or a source of the element such as a thiirane, to a stannylene, or by dechalcogenation of a tetrachalcogenostannolane with triphenylphosphine (Equation (192)). 

Implications for Source Studies. The results discussed above Indicate the need for measurements of a number of elements In studies of particles both from sources and In ambient air. Measurements of Na, Pb, Ca, As, Mn and V are very Important for use In receptor models. Aluminum and Fe are quite useful, but not essential If many other llthophlle elements are measured (e.g., SI, Tl, Sc). Likewise, Zn Is useful, but could be replaced by elements such as Sb and Cd. However, AI, Fe and Zn can usually be measured more easily than their surrogates. Iron and elements such as Cr, Mn, Co and N1 will be Important In areas that have Iron and steel Industries and elements such as Cu, Zn, Pb and other chalcophlles In areas that have non-ferrous metal Industries. Sources of the unexplained Mn, Cr, Cu, Nl, K and Mg In Washington need to be Identified. Thus, we have a set of about 15 elements that should be measured as a minimum, plus others that may provide additional useful Information, e.g., Br, Ba, Cd, Sb. Note that It Is not sufficient to measure a given element only In particles from the dominant source of the element. For example, motor vehicles are the major source of Pb In most areas however, significant amounts are released by refuse Incinerators and non-ferrous smelters. Thus, If the CEB Is to determine the correct source strength for the motor—vehicle component, Pb contributions from the other, less Important sources must be known. 

In the early 1800s, the principal sources of nickel were in Germany and Scandinavia, Very large deposits of lateritic (oxide or silicate) nickel ore were discovered in New Caledonia in 1865. The sulfide ore deposits were discovered in Sudbury, Ontario in 1883 and, since 1905, have been the major source of the element, The most common ore is pentlandite, (FeNi Sg, which contains about 34% nickel. Pent-landite usually occurs with pyrrhotite, an iron-sulfide ore, and chalcopyrite. CuPeS2. See also Chalcopyrite Pentlandite and Pyrrhotite, The greatest known reserves of nickel are in Canada and Russia, although significant reserves also occur in Australia, Finland, the Republic of South Africa, and Zimbabwe. 

Primary sources of the element are bastnasite and monazite, which contain from 4 to 8% praseodymium. Plant capacity involving liquid-liquid or solid-liquid organic ion-exchange processes for recovering the element is in excess of 100.000 pounds PreOn annually. Metallic praseodymium is obtained by electrolysis of Pr O] in a molten fluoride electrolyte, or by a calcium reduction of PrFj or PrCls in a sealed-bomb reaction. 

FIGURE 16.12 Manganese nodules litter the ocean floor and are potentially a valuable source of the element. 

Sulfur is found in large quantities but in various forms throughout the world. It is found in metal ores such as copper pyrites or chalcopyrite (CuFeS2) and zinc blende (ZnS) and in volcanic regions of the world. Natural gas and oil contain sulfur and its compounds, but the majority of this sulfur is removed as it would cause environmental problems. Sulfur obtained from these sources is known as recovered sulfur and it is an important source of the element. It is also found as elemental sulfur in sulfur beds in Poland, Russia and the US (Louisiana). These sulfur beds are typically 200 m below the ground. Sulfur from these beds is extracted using the Frasch process, named after its inventor Hermann Frasch. 

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