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Facts About Arsenic

arsenic
Electron configuration and elemental properties of arsenic.
Credit: Greg Robson/Creative Commons, Andrei Marincas | Shutterstock
Atomic Number: 33
Atomic Symbol: As
Atomic Weight: 74.92160
Melting Point: 1,502.6 F (817 C)
Boiling Point: 1,117.4 F (603 C)

Word origin:  Arsenic comes from the Persian word Zarnikh, meaning "yellow orpiment," which the Greeks adopted as arsenikon. It is also related to the Greek word arsenikos, meaning "masculine" or "potent." The Latin word for it became arsenicum.

orpiment
A crystal cluster of orpiment, an arsenic sulfide found near volcanic hot springs.
Credit: lphoto | Shutterstock

Discovery: Arsenic sulfides and oxides have been known since ancient times. The element was first isolated by Albertus Magnus in 1250. In 1649, German chemist Johann Schroeder discovered two methods of preparing the element.

Properties of arsenic

Arsenic is a crystalline metalloid that is usually steel gray and very brittle. There are two other allotropes, yellow and black. [See Periodic Table of the Elements]

When arsenic comes into contact with the air, it begins to tarnish. When heated, it undergoes rapid oxidization into arsenic oxide. This substance smells strongly of garlic.

Arsenic and its compounds are poisonous.

Sources of arsenic

Arsenopyrite (FeAsS), an iron arsenic sulfide, also called mispickel, is the most common mineral from which arsenic is obtained.  After heating, the mineral sublimes, or changes directly from the solid to the gaseous state without becoming a liquid, and leaves behind ferrous sulfide.

Orpiment, another arsenic sulfide, is a mineral found near volcanic hot springs. Known for its bright yellow color, it was traditionally used as a poison and as a medicine, as well as a pigment for paintings and sealing wax. Today, it is used in the production of linoleum, semiconductors, oil cloth and infrared-transmitting glass. It is used in the tanning industry to remove hair from hides, and as a depilatory.   

Arsenopyrite
A chunk of arsenopyrite, the most common source of arsenic.
Credit: Oreena | Shutterstock

Uses of arsenic

Arsenic is often used as a doping agent for solid-state devices. Gallium arsenide is used in lasers that convert electricity into coherent light.

Arsenic compounds, such as Paris green, calcium arsenate and lead arsenate, are used as insecticides and in other poisons.

Arsenic is used in pyrotechnics to give additional color to the flame. Arsenic improves the sphericity of lead shot.

Arsenic has been used as a poison in history but is easily detectable. To detect arsenic, scientists may use Marsh's test. Named after British chemist James Marsh, the test identifies the presence of arsenic in the field of forensic toxicology.

(Source: Los Alamos National Laboratory)

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