Sulfur Earth abundances

Occurrence. — Titanium is usually regarded as a rare element, but it is one of the 10 more abundant elements in the earth s crust, Ti02 making up 0.73 per cent of the whole lithosphere. It is almost twice as abundant as carbon and exceeds chlorine, phosphorus, and sulfur in abundance. It resembles silicon in its combinations, since it is never found in the free state, but in combination with oxygen either as the simple oxide or as titanates. 

Carbonyl sulfide is overall the most abundant sulfur-beating compound ia the earth s atmosphere 430—570 parts per trillion (10 ), although it is exceeded by H2S and SO2 ia some iadustrial urban atmospheres (27). Carbonyl sulfide is beheved to origiaate from microbes, volcanoes, and the burning of vegetation, as well as from iadustrial processes. It may be the main cause of atmospheric sulfur corrosion (28). 

Oxygen is by far the most abundant element in cmstal rocks, composing 46.6% of the Hthosphere (4). In rock mineral stmctures, the predominant anion is, and water (H2O) itself is almost 90% oxygen by weight. The nonmetaUic elements fluorine, sulfur, carbon, nitrogen, chlorine, and phosphoms are present in lesser amounts in the Hthosphere. These elements aU play essential roles in life processes of plants and animals, and except for phosphoms and fluorine, they commonly occur in earth surface environments in gaseous form or as dissolved anions. 

Iron, Fe, the most widely used of all the d-metals, is the most abundant element on Earth and the second most abundant metal in the Earth s crust (after aluminum). Its principal ores are the oxides hematite, Fe203, and magnetite, Fc C)4. The sulfide mineral pyrite, FeS2 (see Fig. 15.11), is widely available, but it is not used in steelmaking because the sulfur is difficult to remove. 

As can be seen in Fig. 2-1 (abundance of elements), hydrogen and oxygen (along with carbon, magnesium, silicon, sulfur, and iron) are particularly abundant in the solar system, probably because the common isotopic forms of the latter six elements have nuclear masses that are multiples of the helium (He) nucleus. Oxygen is present in the Earth s crust in an abundance that exceeds the amount required to form oxides of silicon, sulfur, and iron in the crust the excess oxygen occurs mostly as the volatiles CO2 and H2O. The CO2 now resides primarily in carbonate rocks whereas the H2O is almost all in the oceans. 

Although the abundance of silver in the Earth s crust is comparatively low (0.07 pgg-1), it is considered an environmental contaminant and is toxic at the nanomolar level. As an environmental pollutant it is derived from mining and smelting wastes and, because of its use in the electrical and photographic industries, there are considerable discharges into the aquatic environment. Consequently, there have been studies on the geochemistry and structure of silver-sulfur compounds [31]. Silver, either bound to large molecules or adsorbed on to particles, is found in the colloidal phase in freshwater. In anoxic sediments Ag(I) can bind to amorphous FeS, but dissolved silver compounds are not uncommon. A more detailed study of silver speciation in wastewater effluent, surface and pore waters concluded that 33-35% was colloidal and ca. 15-20% was in the dissolved phases [32]. 

Cobalt is the 32nd most abundant element on Earth even though it makes up only 0.003% of the Earth s crust. It is not found in the free metallic state, despite being widely distributed in igneous rocks as minerals. Its two most common mineral ores are cobaltite (CoAsS) and erythrite [Co lAsO l ]. These ores are placed in blast furnaces to produce cobalt arsenide (COjAs), which is then treated with sulfuric acid to remove the arsenic. Finally, the product cobalt tetraoxide (Co O ) is reduced by heat with carbon (Co O + C — 3Co + 2COf resulting in cobalt metal. 

ORIGIN OF NAME From the Sanskrit word sulvere and the Latin word sulphurim. ISOTOPES There are a total of 24 isotopes of sulfur all but four of these are radioactive. The four stable isotopes and their contribution to sulfur s total abundance on Earth are as follows S-32 contributes 95.02% to the abundance of sulfur S-33, just 0.75% S-34, 4.21% and S-36, 0.02%. 

Selenium is the 67th most abundant element in Earths crust. It is widely spread over the Earth, but does not exist in large quantities. As a free element it is often found with the element sulfur. 

Although neodymium is the 28th most abundant element on Earth, it is third in abundance of all the rare-earths. It is found in monazite, bastnasite, and allanite ores, where it is removed by heating with sulfuric acid (H SO ). Its main ore is monazite sand, which is a mixture of Ce, La, Th, Nd, Y, and small amounts of other rare-earths. Some monazite sands are composed of over 50% rare-earths by weight. Like most rare-earths, neodymium can be separated from other rare-earths by the ion-exchange process. 

Most of these are relatively common and some are common indeed. For example, silicon and aluminum are the second and third most abundant elements in the Earth s crust. The rarest of these elements, selenium, is twice as abundant as silver and 20 times more abundant than gold, and it is relatively easy to obtain because it often occurs in sulfur deposits. 

Nickel combined with other elements occurs naturally in the earth s crust. It is found in all soil, and is also emitted from volcanos. Nickel is the 24th most abundant element. In the environment it is found primarily combined with oxygen or sulfur as oxides or sulfides. 

The Earth s core is composed of iron-nickel alloy, with an inner solid core surrounded by a molten outer core. A mismatch between the inferred density of the outer core and that predicted for iron-nickel metal at high pressure suggests that some light elements) must dilute the iron in the molten core. Some possibilities are oxygen, sulfur, silicon, and hydrogen, all elements with high cosmic abundances that can alloy with iron at very high... 

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