Arsenic minerals

Geologists define a mineral as a naturally occurring, crystalline, and inorganic solid. Although liquids, gases, synthetic materials, amorphous substances, and organic compounds may contain arsenic, they are not minerals. Arsenic minerals include rhombohedral elemental arsenic, arsenolamprite, pararsenolamprite, and over 320 inorganic compounds (Foster, 2003), 39. Chapter 3 discusses the natural occurrences and potential environmental impacts of several of the more common arsenic minerals. 

Arsenical An arsenic compound. Unlike arsenian minerals, arsenic is a major component in arsenicals (compare with organoarsenical). 

Demesmay and Olle [41] showed that the use of microwave extraction procedures work well for mineral arsenic but may affect the relative amounts of various arsenic species. 

Originally, herbal remedies were often infusions of herbs, but nowadays they may also be produced in more concentrated form, as capsules for example. The possibility of overdosage is therefore present. Because many herbal remedies are available for people to buy and administer themselves without the involvement of a licensed practitioner, some of them may increase the dose on the grounds that, if the recommended dose works, an increased dose wiU be even better. Herbal remedies may be prescribed by practitioners who may be medical herbalists, Chinese herbalists, or A)airvedic or Unani practitioners, for example. These practitioners tend to use herbs from Europe, China, or the Indian subcontinent. In the case of the latter two the remedies may contain constituents such as minerals (arsenic, for example) and parts of animals. 

Arsenic is the twentieth most abundant element in Earth s crust, averaging a concentration of approximately 2 ppm. Arsenopyrite (FeAsS) is its most common mineral. Arsenic occurs widely in nature, and most abundantly in sulfide ores and the products of volcanic eruptions. Arsenic concentrations in rock and soil are highly variable the highest concentrations are in hydrothermal sulfide mineralization areas. 

Spectrophotometric determination. The airborne aerosol is filtered and after the filter mineralization, arsenic compounds are reduced with zinc in HCl medium to arsine. Arsine with a solution of silver diethyldithiocarbamate in pyridine yields a red colour, which is suitable for spectrophotometric determination. The measurement is made at 540 nm [26]. 

In both surface waters and groundwaters, arsenic in the aqueous (mobile) phase is derived from the arsenic contained in soils, rocks, and aquifer minerals. Arsenic... 

Whereas nitrogen and phosphorus were both nonmetals, arsenic (As) and antimony (Sb) are both metalloids. Although phosphorus is normally found in minerals, arsenic and antimony are more often found as sulfides in nature and in significantly smaller quantities. Pure samples of each metalloid are usually dark gray in color. 

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. 

Uranium, not as rare as once thought, is now considered to be more plentiful than mercury, antimony, silver, or cadmium, and is about as abundant as molybdenum or arsenic. It occurs in numerous minerals such as pitchblende, uraninite, carnotite, autunite, uranophane, and tobernite. It is also found in phosphate rock, lignite, monazite sands, and can be recovered commercially from these sources. 

Mineral Feed. Mineral feed supplements for domestic animals and fowl usually contain a pure form of pulverized limestone. In fact, some state laws require the supplement to be at least 35% available calcium. Other sources of calcium are bone meal and dicalcium phosphate. Use as mineral feed has been a steadily growing market for limestone. The material is ground to 90% minus 0.15 mm (100 mesh) or 80% minus 0.9074 mm (200 mesh), is low in silica, and has strict tolerances on arsenic and fluorine (see Feeds and feed additives). 

Some elements found in body tissues have no apparent physiological role, but have not been shown to be toxic. Examples are mbidium, strontium, titanium, niobium, germanium, and lanthanum. Other elements are toxic when found in greater than trace amounts, and sometimes in trace amounts. These latter elements include arsenic, mercury, lead, cadmium, silver, zirconium, beryUium, and thallium. Numerous other elements are used in medicine in nonnutrient roles. These include lithium, bismuth, antimony, bromine, platinum, and gold (Eig. 1). The interactions of mineral nutrients with... 

Under unusual circumstances, toxicity may arise from ingestion of excess amounts of minerals. This is uncommon except in the cases of fluorine, molybdenum, selenium, copper, iron, vanadium, and arsenic. Toxicosis may also result from exposure to industrial compounds containing various chemical forms of some of the minerals. Aspects of toxicity of essential elements have been pubhshed (161). 

Nickel [7440-02-0] Ni, recognized as an element as early as 1754 (1), was not isolated until 1820 (2). It was mined from arsenic sulfide mineral deposits (3) and first used in an alloy called German Silver (4). Soon after, nickel was used as an anode in solutions of nickel sulfate [7786-81 A] NiSO, and nickel chloride [7718-54-9] NiCl, to electroplate jewelry. Nickel carbonyl [13463-39-3] Ni(C02)4, was discovered in 1890 (see Carbonyls). This material, distilled as a hquid, decomposes into carbon monoxide and pure nickel powder, a method used in nickel refining (5) (see Nickel and nickel alloys). 

These precursors are prepared by reaction of fuming nitric acid in excess acetic anhydride at low temperatures with 2-furancarboxaldehyde [98-01-1] (furfural) or its diacetate (16) followed by treatment of an intermediate 2-acetoxy-2,5-dihydrofuran [63848-92-0] with pyridine (17). This process has been improved by the use of concentrated nitric acid (18,19), as well as catalytic amounts of phosphoms pentoxide, trichloride, and oxychloride (20), and sulfuric acid (21). Orthophosphoric acid, -toluenesulfonic acid, arsenic acid, boric acid, and stibonic acid, among others are useful additives for the nitration of furfural with acetyl nitrate. Hydrolysis of 5-nitro-2-furancarboxyaldehyde diacetate [92-55-7] with aqueous mineral acids provides the aldehyde which is suitable for use without additional purification. 

Arsenic is widely distributed about the earth and has a terrestrial abundance of approximately 5 g/t (4). Over 150 arsenic-bearing minerals are known (1). Table 2 fists the most common minerals. The most important commercial source of arsenic, however, is as a by-product from the treatment of copper, lead, cobalt, and gold ores. The quantity of arsenic usually associated with lead and copper ores may range from a trace to 2 —3%, whereas the gold ores found in Sweden contain 7—11% arsenic. Small quantities of elemental arsenic have been found in a number of localities. 

Table 2. Naturally Occurring Arsenic-Bearing Minerals...

Metafile arsenic can be obtained by the direct smelting of the minerals arsenopyrite or loeUingite. The arsenic vapor is sublimed when these minerals are heated to about 650—700°C in the absence of air. The metal can also be prepared commercially by the reduction of arsenic trioxide with charcoal. The oxide and charcoal are mixed and placed into a horizontal steel retort jacketed with fire-brick which is then gas-fired. The reduced arsenic vapor is collected in a water-cooled condenser (5). In a process used by Bofiden Aktiebolag (6), the steel retort, heated to 700—800°C in an electric furnace, is equipped with a demountable air-cooled condenser. The off-gases are cleaned in a sembber system. The yield of metallic arsenic from the reduction of arsenic trioxide with carbon and carbon monoxide has been studied (7) and a process has been patented describing the gaseous reduction of arsenic trioxide to metal (8). 

Minerals Yearbook, Minor Metals bulletin (Arsenic Section), Bureau of Mines, U.S. Dept, of the Interior, Washington D.C., 1988. 

J. R. Loebenstein, Mineral Industry Surveys, Arsenic in 1989 (Annual Keview), Bureau of Mines, U.S. Dept, of Interior, Washington D.C., 1989. Information bulletin. No. 5 and 6, Arsenic Development Committee, Rue LaEayette, Paris, Prance, 1965. 

Lead The production of lead from lead sulphide minerals, principally galena, PbS, is considerably more complicated than the production of zinc because tire roasting of the sulphide to prepare the oxide for reduction produces PbO which is a relatively volatile oxide, and therefore the temperature of roasting is limited. The products of roasting also contain unoxidized galena as well as die oxide, some lead basic sulphate, and impurities such as zinc, iron, arsenic and antimony. 

Carcinogens Cancer-producing agents Skin Respiratory Bladder/urinary tract Liver Nasal Bone marrow Coal tar pitch dust crude anthracene dust mineral oil mist arsenic. Asbestos polycyclic aromatic hydrocarbons nickel ore arsenic bis-(chloromethyl) ether mustard gas. p-naphthylamine benzidine 4-am i nodi pheny lam ine. Vinyl chloride monomer. Mustard gas nickel ore. Benzene. 

None of the three elements is particularly abundant in the earth s crust though several minerals contain them as major constituents. As can be seen from Table 13.1, arsenic occurs about halfway down the elements in order of abundance, grouped with several others near 2 ppm. Antimony has only one-tenth of this abundance and Bi, down by a further factor of 20 or more, is about as unabundant as several of the commoner platinum metals and gold. In common with all the post-transition-element metals. As, Sb and Bi are chalcophiles, i.e. they occur in association with the chalcogens S, Se and Te rather than as oxides and silicates. 

Arsenic minerals are widely distributed throughout the world and small amounts of the free element have also been found. Common... 

SEI f-Test L.4B The amount of arsenic(IIl) oxide in a mineral can be determined by dissolving the mineral in acid and titrating it with potassium permanganate ... 

The magnetic criterion is particularly valuable because it provides a basis for differentiating sharply between essentially ionic and essentially electron-pair bonds Experimental data have as yet been obtained for only a few of the interesting compounds, but these indicate that oxides and fluorides of most metals are ionic. Electron-pair bonds are formed by most of the transition elements with sulfur, selenium, tellurium, phosphorus, arsenic and antimony, as in the sulfide minerals (pyrite, molybdenite, skutterudite, etc.). The halogens other than fluorine form electron-pair bonds with metals of the palladium and platinum groups and sometimes, but not always, with iron-group metals. 

Coal tar pitch dust crude anthracene dust mineral oil mist arsenic. 

Six elements are metalloids B, Si, Ge, As, Sb, and Te. Of these, silicon is by far the most abundant, making up over 27% of the Earth s crust, more than any other element except oxygen, hi fact, S1O2 and silicate minerals account for 80% of the atoms near the Earth s surface. Despite its great abundance, silicon was not discovered until 1824, probably because the strong bonds it forms with oxygen makes silicon difficult to isolate. Two much rarer metalloids, antimony (known to the ancients) and arsenic (discovered ca. 1250 ad) were isolated and identified long before silicon. 

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