arsenic

arsenic
Name	Arsenic
Caption	Elemental arsenic in its gray metallic form
Atomic number	33
Category	Metalloid
Appearance	Steel-gray, brittle
Atomic weight	74.921595
Phase	Solid
Density	5.72 g/cm³
Melting point	817 °C
Boiling point	613 °C (sublimes)

arsenic Arsenic is a chemical element with atomic number 33, classified as a metalloid notable for its allotropes, compounds, and historical associations with medicine, metallurgy, and poisoning. It has shaped developments in Persia, Egypt, Rome, and modern industrial nations through its roles in metallurgy, agriculture, and public health. The element appears in mineral deposits, industrial processes, and biogeochemical cycles that intersect with policy debates involving agencies such as the World Health Organization, the United States Environmental Protection Agency, and national ministries.

Etymology and History

The name derives from medieval Latin and Greek sources encountered by scholars such as Dioscorides and Pliny the Elder and later transmitted through texts used in Renaissance laboratories in Florence and Paris. Historical records link arsenic compounds to poisonings in courts of Louis XIV of France, criminal cases in Victorian era United Kingdom, and forensic investigations that involved figures like Matthew Hopkins-era witch trials in England. Alchemists in Prague and practitioners like Paracelsus experimented with arsenical preparations; later chemists including Antoine Lavoisier and John Dalton contributed to understanding elemental properties. The industrial revolution centered in Great Britain and Germany expanded arsenic use in pigments and metallurgy, leading to environmental legacies documented in regions such as Cornwall and the Silesia mining districts.

Occurrence and Production

Arsenic occurs in minerals such as arsenopyrite, realgar, and orpiment found in mining regions like Bolivia, Peru, China, India, Mexico, United States, and Australia. Major modern production is often a byproduct of copper and gold smelting in facilities run by corporations headquartered in Glencore, BHP, and Rio Tinto operations, with ores processed at plants in Chihuahua, Inner Mongolia, and Arizona. Refining methods evolved from roasting and sublimation practiced in early smelters in Seville and Hamburg to modern hydrometallurgical and pyrometallurgical flowsheets developed at research centers affiliated with Massachusetts Institute of Technology and Imperial College London. International trade of arsenic trioxide and alloys traverses ports such as Rotterdam, Shanghai, and Los Angeles.

Physical and Chemical Properties

Elemental arsenic exhibits allotropy with gray (metallic), yellow (molecular), and black (amorphous) forms, studied by scientists at institutions like University of Cambridge and Harvard University. It forms covalent bonds in compounds studied in coordination chemistry by groups at ETH Zurich and University of California, Berkeley. Arsenic displays oxidation states −3, 0, +3, and +5; its +3 and +5 oxides, arsenous oxide and arsenic pentoxide, are central to reactions described in textbooks from Oxford University Press authors. Electronic structure investigations using facilities such as CERN and Lawrence Berkeley National Laboratory illuminate band structure relevant to semiconductor behavior in devices developed by companies like Intel and Samsung.

Organometallic and Inorganic Compounds

Arsines, arsenates, and arsenites constitute major inorganic families with industrial and biochemical relevance; historical reagents include Fowler's solution promoted in 19th-century clinics in London. Organometallic chemistry of arsenic links to analogues of phosphines explored by research groups at Caltech and Stanford University. Arsenic-containing pesticides, herbicides, and wood preservatives—used by firms historically such as Monsanto and DuPont—include compounds like lead arsenate and chromated copper arsenate; their phase-out involved regulatory actions influenced by cases in California and Queensland.

Biological Roles and Toxicology

Arsenic has no established essential role in human biology, though some microorganisms utilize arsenic in metabolism, documented by researchers from Scripps Institution of Oceanography and Woods Hole Oceanographic Institution. Toxicity manifests acutely and chronically through mechanisms involving inhibition of pyruvate dehydrogenase and disruption of oxidative phosphorylation; clinical cases treated in hospitals such as Mayo Clinic and Johns Hopkins Hospital informed toxicology literature. Notable mass exposures include incidents in Bangladesh and regions of West Bengal linked to contaminated groundwater; epidemiological studies published by teams from Columbia University and Harvard School of Public Health examined cancer risk, skin lesions, and cardiovascular outcomes.

Environmental Impact and Biogeochemistry

Arsenic cycles through soil, sediment, and aquatic systems with mobilization influenced by redox chemistry studied at US Geological Survey labs and universities like University of Washington. Mine tailings in regions near Sierra Nevada and Andes have produced contaminated drainage events addressed by remediation programs administered by United Nations Environment Programme and national agencies. Microbial mediation of arsenic transformation involves genera such as Shewanella and Geobacter investigated at Argonne National Laboratory, informing bioremediation approaches trialed in sites across Vietnam and Nepal.

Uses and Applications

Historically used in pigments like Scheele's green and in medicinal tonics, arsenic later found roles in alloying, semiconductor doping, and wood preservation; companies in Japan and Germany developed arsenide semiconductors for optoelectronics with contributions from labs at Bell Labs and Rutherford Appleton Laboratory. Organometallic arsenic compounds appeared in niche organic synthesis protocols taught in courses at University of Tokyo and Seoul National University. Agricultural uses declined after regulatory restrictions in jurisdictions such as European Union and United States.

Regulation and Public Health Response

Public health standards and remediation policies stem from assessments by the World Health Organization, United States Environmental Protection Agency, European Chemicals Agency, and national ministries exemplified by agencies in Bangladesh and Chile. Drinking water limits, occupational exposure limits, and soil remediation guidelines have been enforced following epidemiological evidence from studies by National Institutes of Health and Centers for Disease Control and Prevention. International cooperation on mining pollution and chemical safety involves agreements and programs linked to organizations such as the United Nations and non-governmental groups like Greenpeace and Doctors Without Borders.

Category:Chemical elements