Realgar

Realgar, α-As4S4, is an arsenic sulfide mineral. It is a soft, sectile mineral occurring in monoclinic crystals, or in granular, compact, or powdery form, often in association with the related mineral, orpiment (As2S3). It is orange-red in colour, melts at 320 °C, and burns with a bluish flame releasing fumes of arsenic and sulfur. Realgar is soft with a Mohs hardness of 1.5 to 2 and has a specific gravity of 3.5. Its molecular weight is 106.99. Its streak is orange colored. Realgar has a sub-metallic luster.

Its name comes from Arabic "rahj al-ghar" – 'powder of the mine,' via Catalan, Middle Latin, and Middle Englishcite book | title=Webster's Third New International Dictionary | publisher=Merriam-Webster, inc. | year=1993 | editor=Philip Babcock Grove | id=ISBN 3-8290-5292-8] , though this comes through a misreading, the original name was "rahj al-fār" – 'rat powder', due to its use as a rodenticideFact|date=September 2008. In India, realgar is known as "manseel", and orpiment as "hartal".

It was, along with orpiment, a significant item of trade in the ancient Roman Empire and was used as a pigment and a medicine. It was also used as a medicine in China and "is made up into household ornaments, such as wine pots, wine cups, images, paperweights, and various other kinds of ornaments and charms, to be kept near at hand in use, or worn about the person, with a view of warding off disease."

It is commonly held that after a long period of exposure to light realgar changes form to a yellow powder known as pararealgar (β-As4S4). It was once thought that this powder was the yellow sulfide orpiment, but has been recently shown to be a distinct chemical compound.

Realgar, orpiment, and arsenopyrite provide nearly all the world's supply of arsenic as a byproduct of smelting concentrates derived from these ores.

Realgar was also used by firework manufacturers to create the color white in fireworks prior to the availability of powdered metals such as Aluminum, Magnesium and Titanium. It is still used in combination with Potassium chlorate to make a contact explosive known as "red explosive" for some types of torpedoes and other novelty exploding fireworks, as well in the cores of some types of crackling stars.

Other traditional uses include manufacturing shot, printing and dyeing calico, and depilating and tanning hides.Realgar is very poisonous. It should be kept in good conditions such as a dark cool place. Wash hands after handling. Do not crush into powder.

Sources

* "The Merck Index: An Encyclopedia of Chemicals, Drugs, and Biologicals". 11th Edition. Ed. Susan Budavari. Merck & Co., Inc., N.J., U.S.A. 1989.
* William Mesny. "Mesny’s Chinese Miscellany. A Text Book of Notes on China and the Chinese." Shanghai. Vol. III, (1899), p. 251; Vol. IV, (1905), pp. 425-426.

External links

* [http://webmineral.com/data/Realgar.shtml Webmineral.com Mineralogy Database: Realgar]
* [http://www.mindat.org/min-3375.html Mindat.org: Realgar]
* [http://www.mindat.org/min-3107.html Mindat.org: Pararealgar]
* American Mineralogist Vol 80, pp 400-403, 1995 [http://www.minsocam.org/msa/AmMin/toc/Articles_Free/1995/Bonazzi_p400-403_95.pdf#search=%22American%20Mineralogist%2C%20Volume%2077%2C%20pages%201266-1274%2C%20%22]
* American Mineralogist Vol 20, pp 1266-1274, 1992 [http://www.minsocam.org/ammin/AM77/AM77_1266.pdf#search=%22American%20Mineralogist%2C%20Volume%2077%2C%20pages%201266-1274%2C%20%22]

References


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Look at other dictionaries:

  • Realgar — auf Calcit aus der Jiepaiyu Mine (Shimen Mine), Hunan, China Chemische Formel As4S4 Mineralklasse nichtmetallartige Sulfide II/F.02 30 (nach …   Deutsch Wikipedia

  • Réalgar — Catégorie II : sulfures et sulfosels[1] Réalgar, Roumanie …   Wikipédia en Français

  • Realgar — Réalgar Réalgar Catégorie II : sulfures et sulfosels Réalgar, Pochodzenie, Baia Sprie Roumani …   Wikipédia en Français

  • réalgar — [ realgar ] n. m. • 1495; reagal mil. XIVe; altér. de l ar. rehj al ghar « poudre de cave; mort aux rats » ♦ Alchim., minér. Sulfure naturel d arsenic (As2S2) de couleur rouge. ● réalgar nom masculin (espagnol rejalgar, de l arabe rahdj al rhār,… …   Encyclopédie Universelle

  • realgar — REALGÁR s.n. Minereu constituit din sulfura naturală de arsen cristalizată în sistemul monoclinic, de culoare portocalie, având numeroase folosiri în vopselărie, extragerea arsenului, industria sticlei, în pirotehnie etc. [pr.: re al ] – Din fr.… …   Dicționar Român

  • realgar — reàlgār m <G realgára> DEFINICIJA min. crveni arsenov sulfid AsS, upotrebljava se za spravljanje arsenskih preparata ETIMOLOGIJA njem. Realgar fr. réalgar ← arap. rahj al ghār: prah iz rudnika ili spilje …   Hrvatski jezični portal

  • Realgar — Re*al gar (r[ e]*[a^]l g[ e]r), n. [F. r[ e]algar, Sp. rejalgar, Ar. rahj al gh[=a]r powder of the mine.] (Min.) Arsenic sulphide, a mineral of a brilliant red color; red orpiment. It is also an artificial product. [1913 Webster] …   The Collaborative International Dictionary of English

  • Realgar — (arab.), 1) alte Benennung des Arsenikrubins, s. u. Arsenik I. C) b); 2) so v.w. Rother Schwefelarsen (As S2), s. u. Arsen G) a) …   Pierer's Universal-Lexikon

  • Realgār — (Rauschrot, Rotrauschgelb, rote Arsenblende), Mineral, besteht aus Schwefelarsen As S mit 70 Teilen Arsen, findet sich in säuligen monoklinen Kristallen aufgewachsen oder eingesprengt, auch als Anflug und Überzug, morgenrot mit orangegelbem… …   Meyers Großes Konversations-Lexikon

  • Realgar — Realgar, s. Arsensulfide, Bd. 1, S. 305 …   Lexikon der gesamten Technik


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