Rare elements

Titanium is not a rare element it is the most abundant transition metal after iron, and is widely distributed in the earth s surface, mainly as the dioxide TiOj and ilmenite FeTi03. It has become of commercial importance since World War II mainly because of its high strength-weight ratio (use in aircraft, especially supersonic), its... 

Wangzhao, Z., Advanced Inductively Coupled Plasma Mass Spectrometry Analysis of Rare Elements, Balkema Publishers, 1999. 

Occurrence in Nature. About 99.6% of the earth s mass results from 32 of the chemical elements. The remaining 0.4% is apportioned among 64 elements, all of which are present as traces. Iodine is one of these 64. Estimates about abundance of the constituent elements of the Hthosphere place iodine 46th on a restricted Hst of 59 elements (37 very rare elements are excluded) and 61st on a Hst in which 96 elements are included. Iodine is, indeed, one of the scarcest of the nonmetaUic elements in the total composition of the earth (3). 

M. A. Filyand and E. I. Semenova, Handbook of the Rare Elements, MacDonald, London, 1969. 

In the present time our organosilicon adsorbents found the practice application in such as fields such as, for example 1) the method of spectral-chemical determination of gold Clarke quantities in poor ores and rocks has been applied in analytic practice of geological establishments and research institutes 2) at the first time soi ption process was used in hydro-chemical analyze of fresh water. This method has been allowed to analyze of Baikal water 3) for purification metallurgical waters and waste solutions of chemical-metallurgical plants due to toxic elements 4) for creation the filters for extraction of rare elements, for example, uranium 5) for silver utilization from wasted of cinema-photo manufactory. This method has been applied to obtain the silver of high purity. 

Ruthenium and osmium are generally found in the metallic state along with the other platinum metals and the coinage metals. The major source of the platinum metals are the nickel-copper sulfide ores found in South Africa and Sudbury (Canada), and in the river sands of the Urals in Russia. They are rare elements, ruthenium particularly so, their estimated abundances in the earth s crustal rocks being but O.OOOl (Ru) and 0.005 (Os) ppm. However, as in Group 7, there is a marked contrast between the abundances of the two heavier elements and that of the first. 

Rhodium and iridium are exceedingly rare elements, comprising only 0.0001 and 0.001 ppm of the earth s crust respectively, and even... 

Niobium and tantalum are rare elements. The content of niobium and of tantalum in the Earth s crust is lxl0"3 and 2x1 O 4 wt. %, respectively [21]. Niobium and tantalum are encountered in nature together, mostly in the form of oxides that are derived from orthoniobic (orthotantalic), metaniobic (metatantalic) and pyroniobic (pyrotantalic) acids. The main minerals are listed in Table 2, which reveals that the most important source of tantalum and niobium is tantalite-columbite, (Fe,Mn)(Nb,Ta)206. 

B. Egovska-Trshebyatovska, S. Kopach, T. Mikulsky, Rare elements, Mir, Moscow, 1979 (in Russian, translation from Polish). 

R.L. Davidovich, Yu.A. Buslaev, Chemical and physic-chemical methods of separations of compounds containing light and rare elements, SO AN SSSR, Vladivostok, 1968, p. 107 (in Russian). 

S.A. Kuznetsov, P.T. Stangrit, Physicochemical investigations of rare elements and the processes of their separation from mineral raw material, Apatity, 1980, p. 25 (in Russian). 

Not surprisingly, only about 20 of the chemical elements found on Earth are used by living organisms (Chapters 3 and 8). Most of them are common elements. Rare elements are used, if at all, only at extremely low concentrations for specialized functions. An example of the latter is the use of molybdenum as an essential component of nitrogenase, the enzyme that catalyzes the fixation of elemental dinitrogen. Because they are composed of common elements, living organisms exert their most profound effects on the cycles of those elements. 

The formation of triiodothyronine (T3) and tetra-iodothyronine (thyroxine T4) (see Figure 42—2) illustrates many of the principles of diversity discussed in this chapter. These hormones require a rare element (iodine) for bioactivity they are synthesized as part of a very large precursor molecule (thyroglobuhn) they are stored in an intracellular reservoir (colloid) and there is peripheral conversion of T4 to T3, which is a much more active hormone. 

Indium (In) is a relatively rare element that never occurs as a free metal. It is usually found in a compound that contams 70.48% In and 29.52% S. What is the empirical formula for this compound ... 

Uranium is not a very rare element. It is widely disseminated in nature with estimates of its average abundance in the Earth s crust varying from 2 to 4 ppm, close to that of molybdenum, tungsten, arsenic, and beryllium, but richer than such metals as bismuth, cadmium, mercury, and silver its crustal abundance is 2.7 ppm. The economically usable tenor of uranium ore deposits is about 0.2%, and hence the concentration factor needed to form economic ore deposits is about 750. In contrast, the enrichment factors needed to form usable ore deposits of common metals such as lead and chromium are as high as 3125 and 1750, respectively. 

P. Cewmy, Rare Element Granitic Pegmatites, Pt. I. Anatomy and Internal Evolution of Pegmatite Deposits, Geoscience Canada, vol. 18, No. 2, 49,1991. 

In that one percent, iron, sodium, calcium, rare elements like scandium, and even elements not found on earth, like technetium, have been discovered. These elements and many others can be identified in the atmospheres of stars by spectroscopy, a method of analyzing the light emitted by our sun and other stars. Each element, whether on the earth or outside of it, always produces a certain, characteristic pattern of colored lines of light when... 

It is important to note that we have tried to avoid carbon-rich stars, because they have a rich molecular line spectrum, mostly CN, CH and C2, obliterating many interesting atomic lines of rare elements. This is why we had in our sample a star, CS 31082-001, in which we were able to measure the 385.97 nm line of U II, whereas in the similar r-process element enriched star CS 22892-052, but carbon rich, a CN line obliterates the U II line. 

Ruhling, A. Tyler, G. 2004. Changes in the atmospheric deposition of minor and rare elements between 1975 and 2000 in south Sweden, as measured by moss analysis. Environmental Pollution 131.3, 417-23. 

The reference to keltium is to a rare element which the French chemist G. Urbain claimed to have discovered. Moseley was able convince Urbain that keltium did not exist (Heilbronn 1974). 

The unique chemical composition of cosmogenous debris has provided some insight into why approximately 70% of the species of organisms on Earth were driven extinct over a relatively short time interval approximately 66 million years ago. Evidence for this mass extinction has been observed in marine sediments throughout all the ocean basins. In a contemporaneous layer deposited at the end of the Cretaceous period, the hard parts of many species of marine plankton abruptly vanished from the sedimentary record. This sedimentary layer is also characterized by a large enrichment in the rare element iridium. 

Evidence also exists for a terrestrial source of the iridium enrichment as volcanic ejecta is enriched in this rare element. Thus, the enriched sediment layer could also have been caused by an abrupt and large increase in volcanic activity. Evidence for this is suggested by high levels of volcanic ash, soot, and shocked minerals in the iridium-enriched layer. Other geochemical characteristics of this sediment layer appear to have been caused by acid rain and tsunamis, both of which are by-products of volcanic activity. 

Zirconium is not a rare element. It is found over most of Earth s crust and is the 18th most abundant element, but it is not found as a free metal in nature. 

Ruthenium is a rare element that makes up about 0.01 ppm in the Earth s crust. Even so, it is considered the 74th most abundant element found on Earth. It is usually found in amounts up to 2% in platinum ores and is recovered when the ore is refined. It is difficult to separate from the leftover residue of refined platinum ore. 

Even though hafnium is not a scarce or rare element, it was not discovered until 1923 because of its close association with zirconium. Several scientists suspected that another element was mixed with zirconium but could not determine how to separate the two because zirconium ore contains about 50 times more zirconium than hafnium. Mendeleev predicted that there was an element with the atomic number of 72, but he predicted it would be found in titanium ore, not zirconium ore. 

Even though polonium is a rare element, it is a very dangerous radiation source and should be avoided. 

Astatine is located just below iodine, which suggests that it should have some of the same chemical properties as iodine, even though it also acts more hke a metal or semimetal than does iodine. It is a fairly heavy element with an odd atomic number, which assisted chemists in learning more about this extremely rare element. The 41 isotopes are man-made in atomic reactors, and most exist for fractions of a second. The elements melting point is about 302°C, its boiling point is approximately 337°C, and its density is about 7g/cm. ... 

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