Chromium minerals

Clearly, some scientific findings demonstrate that if dietary intakes of certain minerals (chromium, copper, iron, manganese, and selenium) are extremely low, if the diet includes toxic minerals (arsenic, cadmium, lead, and mercury), hair analysis can detect these changes. Furthermore, some disorders such as anemia, hepatitis, hyperthyrosis and nephrocalcinosis are reported to change the mineral levels in the hair. 

Nutritional deficiencies—Recent reports in the medical literature have indicated that certain nutritional deficiencies may result from the long-term use of some proprietary brands of TPN infusions, unless the nutrients not present in the solutions are provided by other means. The deficiencies reported up to now have been those of essential fatty acids, the essential minerals chromium and selenium, and the vitamin biotin. Normally, biotin is synthesized by intestinal bacteria, but the administration of broad spectrum antibiotics in the case reported eliminated that source of the vitamin. 

Minerals Chromium, cobalt, copper, iron, manganese, molybdenum, nickel, selenium, silicon, vanadium, zinc... 

Because of its position in the Periodic Table, molybdenum has sometimes been linked to chromium (see Chromiumand chromium alloys) or to other heavy metals. However, unlike those elements, molybdenum and its compounds have relatively low toxicity, as shown in Table 3. On the other hand, molybdenum has been identified as a micronutrient essential to plant life (11,12) (see Fertilizers), and plays a principal biochemical role in animal health as a constituent of several important enzyme systems (see Mineral nutrients). 

Brewers and bakers dried yeasts are used as dietary supplements. They contribute some protein and trace minerals, and some B vitamins, but no vitamin C, vitamin B 2 or fat-soluble vitamins. The glucose tolerance factor (GTE) of yeast, chromium nicotinate, mediates the effect of insulin. It seems to be important for older persons who caimot synthesize GTE from inorganic dietary chromium. The ceU wall fraction of bakers yeast reduces cholesterol levels in rats fed a hypercholesteremic diet. 

Zirconium occurs naturally as a siUcate in zircon [1490-68-2] the oxide baddeleyite [12036-23-6] and in other oxide compounds. Zircon is an almost ubiquitous mineral, occurring ia granular limestone, gneiss, syenite, granite, sandstone, and many other minerals, albeit in small proportion, so that zircon is widely distributed in the earth s cmst. The average concentration of zirconium ia the earth s cmst is estimated at 220 ppm, about the same abundance as barium (250 ppm) and chromium (200 ppm) (2). 

Zn, Ni, Cu, and W, yet is the seventh most abundant element overall because Cr is concentrated in the earth s core and mantle (1,2). It has atomic number 24 and belongs to Group 6 (VIB) of the Periodic Table and is positioned between vanadium and manganese. Other Group 6 members are molybdenum and tungsten. On a toimage basis, chromium ranks fourth among the metals and thirteenth of aU mineral commodities in commercial production. 

Chromium was first isolated and identified as a metal in 1789 by Vauquelin who was working with a rare mineral, Siberian red lead or crocoite [14654-05-08] PbCrO (3). The name chromium comes from the Greek word chroma color and resulted from the wide variety of brilliant colors... 

J. H. DeYoung, M. P. Lee, and B. R. Lipin, International Strategic Minerals Inventory Summary Keport-Chromium USGS Circular 930-B, 1984, 41 pp. 

D. Peckner and I. M. Bernstein, Handbook of Stainless Steels, McGraw-HiU Book Co., New York, 1977, 1200 pp. Miner. Yearb. 1980 and 1984 ed.. Chromium Mineral Industry Surveys, 1990. 

The first chromium compound was discovered in the Ural mountains of Russia, during the latter half of the eighteenth century. Crocoite [14654-05-8] a natural lead chromate, found immediate and popular use as a pigment because of its beautihil, permanent orange-red color. However, this mineral was very rare, and just before the end of the same century, chromite was identified as a chrome bearing mineral and became the primary source of chromium [7440 7-3] and its compounds (1) (see Chromiumand chromium alloys). 

Ghromium(II) Compounds. The Cr(II) salts of nonoxidizing mineral acids are prepared by the dissolution of pure electrolytic chromium metal ia a deoxygenated solution of the acid. It is also possible to prepare the simple hydrated salts by reduction of oxygen-free, aqueous Cr(III) solutions using Zn or Zn amalgam, or electrolyticaHy (2,7,12). These methods yield a solution of the blue Cr(H2 0)g cation. The isolated salts are hydrates that are isomorphous with and compounds. Examples are chromous sulfate heptahydrate [7789-05-17, CrSO 7H20, chromous chloride hexahydrate... 

When Cr202 is introduced as an impurity into the a-Al202 lattice, as occurs in the semiprecious mineral mby, the color is red rather than the normal green. This color anomaly is the result of ligand field splitting of the Cr(III) ion (51,52). Chromium (ITT) also colors other minerals (53). 

Man-made mineral fibre Mixed hydrocarbons (C3 to CIO) m air Total hexavalent chromium compounds in air Aromatic carboxylic acid anhydndes m air... 

Finally, in 1797, the Frenchman L. N. Vauquelin discovered the oxide of a new element in a Siberian mineral, now known as crocoite (PbCr04), and in the following year isolated the metal itself by charcoal reduction. This was subsequently named chromium (Greek xpco ia, chroma, colour) because of the variety of colours found in its compounds. Since their discoveries the metals and their compounds have become vitally important in many industries and, as one of the biologically active transition elements, molybdenum has been the subject of a great deal of attention in recent years, especially in the field of nitrogen fixation (p. 1035). 

In de-aerated 10sulphuric acid (Fig. 3.45) the active dissolution of the austenitic irons occurs at more noble potentials than that of the ferritic irons due to the ennobling effect of nickel in the matrix. This indicates that the austenitic irons should show lower rates of attack when corroding in the active state such as in dilute mineral acids. The current density maximum in the active region, i.e. the critical current density (/ ii) for the austenitic irons tends to decrease with increasing chromium and silicon content. Also the current densities in the passive region are lower for the austenitic irons... 

The precipitate is soluble in free mineral acids (even as little as is liberated by reaction in neutral solution), in solutions containing more than 50 per cent of ethanol by volume, in hot water (0.6 mg per 100 mL), and in concentrated ammoniacal solutions of cobalt salts, but is insoluble in dilute ammonia solution, in solutions of ammonium salts, and in dilute acetic (ethanoic) acid-sodium acetate solutions. Large amounts of aqueous ammonia and of cobalt, zinc, or copper retard the precipitation extra reagent must be added, for these elements consume dimethylglyoxime to form various soluble compounds. Better results are obtained in the presence of cobalt, manganese, or zinc by adding sodium or ammonium acetate to precipitate the complex iron(III), aluminium, and chromium(III) must, however, be absent. 

We have already noted that the transport of pre-boiler corrosion debris to the boiler section includes the oxides of iron, copper, nickel, and zinc (sometimes also chromium) and in higher-pressure boilers transport minerals may further include ... 

A homogeneous mixture of two or more components, whether solid, liquid, or gaseous, is called a solution. Solutions have variable composition while pure substances do not. That is, the relative amounts of the various components in a solution can vary. Thus, air, salt water, and sixteen carat gold are each solutions. The gemstone, ruby, is also a solution since it consists of the mineral corundum (AI2O3) with some of the aluminum replaced by chromium to give the crystal its characteristic color. Since the amount of chromium present can be varied, ruby is a solution. 

Chromium, Cr, is a bright, lustrous, corrosion-resistant metal. Its name, which comes from the Greek word for color, was inspired by its colorful compounds. The metal is obtained from the mineral chromite, FeCr204, by reduction with carbon in an electric arc furnace ... 

The green color suggests chromium or copper but the blue solution formed when the mineral is dissolved in sulfuric acid points to copper as the metal (CuS04 is blue). The colorless gas that forms either upon heating or on treatment with acid is carbon dioxide this is proven when the gas is bubbled into limewater (the cloudiness in the solution is due to CaCO. formation). C02 is formed when carbonates are either heated or treated with acid. The mineral is most likely basic copper(ll) carbonate (Cu2C03(0H)2). 

The fluorine titration of chromium oxide was carried out at the Elf-Atochem Research Center, Pieire-Benite.The catalyst mineralization was carried out in a Parr bomb by reaction with sodium peroxyde. Fluorine ions were then titrated by a potentiometric method with a specific fluoride electrode. 

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