Arsenic - Wikipedia

Arsenic is a chemical element in the periodic table that has the symbol As and atomic number 33. This is a very poisonous metalloid that has three allotropic forms; yellow, black and grey. Arsenic and its compounds are used as herbicides and insecticides and various alloys.

Table of contents

1 Notable Characteristics

2 Applications

3 History

4 Occurrence

5 Precautions

6 External Links

Notable Characteristics

Arsenic is chemically very similar to its predecessor phosphorus, so much so that it will partly substitute for it in biochemical reactions and is thus poisonous. When heated it rapidly oxidizes to arsenous oxide, which has a garlic odor. Arsenic and some arsenic compounds can also sublime upon heating, converting to gaseous form directly. Elemental arsenic is found in two solid forms: yellow and gray/metallic, with [specific gravities of 1.97 and 5.73, respectively.

Applications

Lead arsenate has been used, well into the 20th century, as a pesticide on fruit trees (resulting in neurological damage to those working the sprayers), and copper arsenate has even been recorded in the 19th century as a coloring agent in sweets. Other uses;

Various agricultural insecticides and poisons.
Gallium arsenide is an important semiconductor material, used in integrated circuits. Circuits made using the compound are much faster (but also much more expensive) than those made in silicon. Unlike silicon it is direct bandgap, and so can be used in is used in laser diodes and LEDs to directly convert electricity into light.
Arsenic trioxide has been used in hematology to treat patients with acute promyelocytic leukemia[?] that are resistant to ATRA[?] treatment
Also used in; bronzing[?], pyrotechny[?]

History

Arsenic (Greek arsenikon, meaning "yellow orpiment") has been known and used since ancient times. It has been frequently used for murder, the symptoms of arsenic poisoning being somewhat ill-defined, until the advent of the Marsh test, a sensitive chemical test for its presence.

Albertus Magnus is believed to have been the first to isolate the element in 1250. In 1649 Johann Schroeder[?] published two ways of preparing arsenic.

Occurrence

Arsenopyrite also called mispickel (Fe SAs) is the most common mineral from which, on heating, the arsenic sublimes leaving ferrous sulfide.

The most important compounds of arsenic are white arsenic, its sulfide, Paris green, calcium arsenate, and lead arsenate. Paris green, calcium arsenate, and lead arsenate have been used as agricultural insecticides and poisons. It is sometimes found native, but usually combined with silver, cobalt, nickel, iron, antimony, or sulfur.

Precautions

Arsenic and many of its compounds are especially potent poisons. Arsenic kills by massively disrupting the digestive system, leading to death from shock. See arsenic poisoning.

External Links

WebElements.com - Arsenic (http://www.webelements.com/webelements/elements/text/As/index.html)
EnvironmentalChemistry.com - Arsenic (http://environmentalchemistry.com/yogi/periodic/As.html)