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ARSENIC

(L. arsenicum, Gr. arsenikon, yellow orpiment-identified with arsenikos, male, from the belief that metals were different sexes-Arab. az-zernikh, the orpiment from Persian zerni-zar. gold)

As at. wt. 74.9216
   at. no. 33 
   m.p. 613°C yellow
   m.p. 817°C (28 atm.) gray (ordinary metallic) 
   sp. gr. 1.97 yellow
   sp. gr. 5.73 gray
   valence -3, 0, +3 or -5.
Electronic configuration
 SHELL  K L M N O P Q
 SUB  SHELL He Neon Argon Krypton Xenon Radon Eka-radon
1s 2s 2p 3s 3p 3d 4s 4p 4d 5s 5p 4f 5d 6s 6p 5f 6d 7s 7p
Arsenic 1s22s22p63s23p63d104s24p3      
Symbol 4S3/2
Arsenic occurs in two solid modifications: yellow, and gray or metallic. Gray arsenic, is the ordinary stable form, and sublimes at 613°C. Several other allotropic forms of arsenic are reported in the literature. It is believed that Albertus Magnus obtained the element in 1250 A.D. In 1649 Schroe- der published two'methods of preparing~~the element. It is found native, in the sulfides realgar and' orpiment, as arsenides and sulfarsenides of heavy metals, as the oxide, and as arsenates. Mispickel or arsenopyrite (FeSAs) is the most common mineral, from which on heating the arsenic sublimes leaving ferrous sulfide. The element is a steel gray, very brittle, crystalline, semi-metallic solid; it tarnishes in air, and when heated is rapidly oxidized to arsenous oxide (As2O3) with the odor of garlic. Arsenic and its compounds are poisonous. The maximum allowable concentration of arsenic is recommended to be 0.5 mg/cu. meter of ai?. Arsenic is also used in bronzing, pyrotechny, and for harden- ing and improving the sphericity of shot. The most important compounds are white arsenic (As2O3), the sulfide, Paris green 3Cu(AsO2)~~Cu(C2H3O2)2, calcium arsenate, and lead arsenate, the last three being used as agricultural insecticides and poisons. Marsh's test makes use of the formation and ready decomposition of arsine (AsH3). Arsenic is available in high-purity form. It is finding increas- ing uses as a doping agent in solid-state devices, such as transistors. Gallium arsenide is used as a laser material to convert electricity directly into coherent light.

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