Poisons chemical elements

The term heavy metal refers to any metallic chemical element that has a relatively high density (nsnally specific density of more than 5 g/mL) and is toxic or poisonous at low concentrations. Examples of heavy metals include arsenic (As), cadmium (Cd), chromium (Cr), mercury (Hg), lead (Pb), and thallium (Tl). The sources, uses, and environmental effects of several exemplary specific metals are discussed briefly here. 

FLUORINE. CAS 7782-41-4], Chemical element symbol F. at. no. 9. at. wt. 18.9984, periodic table group 17 (halogens), mp -2l9,62nC, bp - 188.1°C. density 1.696 g/l (gas at 0CC, 1.108 g/cm (liquid at bp). Fluorine is a pale yellow gas, poisonous, very reaclive. combines with most other elements in the dark, except it does not combine readily with oxygen. Critical pressure is 55 atm critical temperature is -129.2 C. First identified by Scheele in 1771. but not isolated until 1886 by Moissan who electrolyzed fused potassium hydrogen fluoride in a platinum apparatus. Fluorine is a high-tonnage chemical, used mainly in the production of fluorides, in the synthesis of fluorocarbons, and us rut oxidizer for rocket fuel. 

The Kentucky medical examiner came to a conclusion. He said the amount of arsenic found in Taylor s samples was several hundred times less than what could be expected had the president been poisoned by arsenic. So although some people still wonder whether Taylor was poisoned, arsenic was not the chemical element used. 

The heavy metal in the environment collocation refers to any metallic chemical element and some metalloids (e.g. arsenic) that are toxic or poisonous for living organisms even at low concentration, e.g. Pb, Cd, Hg, As, H, Cr. They originate in the Earth s crust as well as in the majority of wastes resulting from anthropogenic activities. Toxic effects of other heavy metals (Cr, Mo, Ni, As, Se etc.) have to be considered separately from the effects of biologic doses in which they exert their vital role. 

As is one of the few chemical elements which is universally associated with the word poison . This reputation is not undeserved, for over the centuries, many deaths can be attributed to the administration of arsenic trioxide as inheritance powder . The metalloid has a dual reputation, for its use in medicine in earlier times is equally well documented. As was widely prescribed to treat skin diseases, fevers, malarial disorders, syphilis, lumbago, epilepsy, anemia, ulcers, etc ... 

The result of the electrolysis of molten sodium chloride (Figure 8.2, page 256) is the production of the chemical elements sodium (a soft, very reactive solid at normal conditions of temperature and pressure) and chlorine (a yellowish, reactive and poisonous gas). 

The mention of this chemical element makes most people think of the chrome plating on the bumpers and body trim of their automobiles. However, it was recently discovered that the shiny metal may also exist in forms which function as (7) an essential element, (2) a hormone, (3) a vitamin, and (4) a poison. 

White phosphorus. This element burns in air and can produce severe thermal and chemical burns. It may reignite on drying. After washing, rapid but brief treatment with copper sulphate (to avoid systemic absorption and copper poisoning) is used to convert the phosphorus to copper phosphide which is then removed Hydrogen fluoride. This can form painful but delayed necrosis. Treat with calcium gluconate locally and monitoring of serum calcium levels, with administration of calcium where necessary... 

The elements in a compound are not just mixed together. Their atoms are actually joined, or bonded, to one another in a specific way due to a chemical change (see Section A). The result is a substance with chemical and physical properties different from those of the elements that form it. For example, when sulfur is ignited in air, it combines with oxygen from the air to form the compound sulfur dioxide. Solid yellow sulfur and odorless oxygen gas produce a colorless, pungent, and poisonous gas (Fig. C.l). 

Until quite recently, chemical interest in the metalloids consisted mainly of isolated curiosities, such as the poisonous nature of arsenic and the mildly therapeutic value of borax. The development of metalloid semiconductors, which we describe in Chapter 10, focused intense study on these elements. 

Analytical electron microscopy permits structural and chemical analyses of catalyst areas nearly 1000 times smaller than those studied by conventional bulk analysis techniques. Quantitative x-ray analyses of bismuth molybdates are shown from lOnm diameter regions to better than 5% relative accuracy for the elements 61 and Mo. Digital x-ray images show qualitative 2-dimensional distributions of elements with a lateral spatial resolution of lOnm in supported Pd catalysts and ZSM-5 zeolites. Fine structure in CuLj 2 edges from electron energy loss spectroscopy indicate d>ether the copper is in the form of Cu metal or Cu oxide. These techniques should prove to be of great utility for the analysis of active phases, promoters, and poisons. 

Intrinsic Activity Poisons. These poisons decrease the activity of the catalyst for the primary chemical reaction by virtue of their direct electronic or chemical influence on the catalyst surface or active sites. The mechanism appears to be one that involves coverage of the active sites by poison molecules, removing the possibility that these sites can subsequently adsorb reactant species. Common examples of this type of poisoning are the actions of compounds of elements of the groups Vb and VIb (N, P, As, Sb, O, S, Se, Te) on metallic catalysts. 

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