Английская Википедия:Arsenic trisulfide
Шаблон:Chembox Arsenic trisulfide is the inorganic compound with the formula Шаблон:Chem2. It is a dark yellow solid that is insoluble in water. It also occurs as the mineral orpiment (Latin: auripigmentum), which has been used as a pigment called King's yellow. It is produced in the analysis of arsenic compounds. It is a group V/VI, intrinsic p-type semiconductor and exhibits photo-induced phase-change properties.Шаблон:Cln
Structure
Шаблон:Chem2 occurs both in crystalline and amorphous forms. Both forms feature polymeric structures consisting of trigonal pyramidal As(III) centres linked by sulfide centres. The sulfide centres are two-fold coordinated to two arsenic atoms. In the crystalline form, the compound adopts a ruffled sheet structure.[1] The bonding between the sheets consists of van der Waals forces. The crystalline form is usually found in geological samples. Amorphous Шаблон:Chem2 does not possess a layered structure but is more highly cross-linked. Like other glasses, there is no medium or long-range order, but the first co-ordination sphere is well defined. Шаблон:Chem2 is a good glass former and exhibits a wide glass-forming region in its phase diagram.
Properties
It is a semiconductor, with a direct band gap of 2.7 eV.[2] The wide band gap makes it transparent to infrared light between 620 nm and 11 µm.
Synthesis
From the elements
Amorphous Шаблон:Chem2 is obtained via the fusion of the elements at 390 °C. Rapid cooling of the reaction melt gives a glass. The reaction can be represented with the chemical equation:
Aqueous precipitation
Шаблон:See also Шаблон:Chem2 forms when aqueous solutions containing As(III) are treated with Шаблон:Chem2. Arsenic was in the past analyzed and assayed by this reaction, which results in the precipitation of Шаблон:Chem2, which is then weighed. Шаблон:Chem2 can even be precipitated in 6 M HCl. Шаблон:Chem2 is so insoluble that it is not toxic.
Reactions
Upon heating in a vacuum, polymeric Шаблон:Chem2 "cracks" to give a mixture of molecular species, including molecular Шаблон:Chem2.[3][4] Шаблон:Chem2 adopts the adamantane geometry, like that observed for Шаблон:Chem2 and Шаблон:Chem2. When a film of this material is exposed to an external energy source such as thermal energy (via thermal annealing [5]), electromagnetic radiation (i.e. UV lamps, lasers,[6] electron beams)[7]), As4S6 polymerizes:
Шаблон:Chem2 characteristically dissolves upon treatment with aqueous solutions containing sulfide ions.Шаблон:Cln The dissolved arsenic species is the pyramidal trithioarsenite anion Шаблон:Chem2:
Шаблон:Chem2 is the anhydride of the hypothetical trithioarsenous acid, Шаблон:Chem2. Upon treatment with polysulfide ions, Шаблон:Chem2 dissolves to give a variety of species containing both S–S and As–S bonds. One derivative is Шаблон:Chem2, an eight-membered ring that contains 7 S atoms and 1 As atom, and an exocyclic sulfido center attached to the As atom. Шаблон:Chem2 also dissolves in strongly alkaline solutions to give a mixture of [[trithioarsenite|Шаблон:Chem2]] and [[arsenite|Шаблон:Chem2]].[8]
"Roasting" Шаблон:Chem2 in air gives volatile, toxic derivatives, this conversion being one of the hazards associated with the refining of heavy metal ores:
Contemporary uses
As an inorganic photoresist
Due to its high refractive index of 2.45 and its large Knoop hardness compared to organic photoresists, Шаблон:Chem2 has been investigated for the fabrication of photonic crystals with a full-photonic band-gap. Advances in laser patterning techniques such as three-dimensional direct laser writing (3-D DLW) and chemical wet-etching chemistry, has allowed this material to be used as a photoresist to fabricate 3-D nanostructures.[9][10]
Шаблон:Chem2 has been investigated for use as a high resolution photoresist material since the early 1970s,[11][12] using aqueous etchants. Although these aqueous etchants allowed for low-aspect ratio 2-D structures to be fabricated, they do not allow for the etching of high aspect ratio structures with 3-D periodicity. Certain organic reagents, used in organic solvents, permit the high-etch selectivity required to produce high-aspect ratio structures with 3-D periodicity.
Medical applications
Шаблон:Chem2 and Шаблон:Chem2 have been investigated as treatments for acute promyelocytic leukemia (APL).
For IR-transmitting glasses
Arsenic trisulfide manufactured into amorphous form is used as a chalcogenide glass for infrared optics. It is transparent for light between wavelengths of 620 nm and 11 µm. The arsenic trisulfide glass is more resistant to oxidation than crystalline arsenic trisulfide, which minimizes toxicity concerns.[13] It can be also used as an acousto-optic material.
Arsenic trisulfide was used for the distinctive eight-sided conical nose over the infra-red seeker of the de Havilland Firestreak missile.
Role in ancient artistry
Шаблон:Main The ancient Egyptians reportedly used orpiment, natural or synthetic, as a pigment in artistry and cosmetics.
Miscellaneous
Arsenic trisulfide is also used as a tanning agent. It was formerly used with indigo dye for the production of pencil blue, which allowed dark blue hues to be added to fabric via pencil or brush.
Precipitation of arsenic trisulfide is used as an analytical test for presence of dissimilatory arsenic-reducing bacteria (DARB).[14]
Safety
Шаблон:See also Шаблон:Chem2 is so insoluble that its toxicity is low. Aged samples can contain substantial amounts of arsenic oxides, which are soluble and therefore highly toxic.
Natural occurrence
Orpiment is found in volcanic environments, often together with other arsenic sulfides, mainly realgar. It is sometimes found in low-temperature hydrothermal veins, together with some other sulfide and sulfosalt minerals.
References
Further reading
- Шаблон:IARC arsenic.
- "Arsenic Compounds, Inorganic", Report on Carcinogens, Eleventh Edition (PDF), U.S. Department of Health and Human Services, Public Health Service, National Toxicology Program, 2005.
External links
- UK Poison Information Document
- Шаблон:EHC
- Шаблон:PIM
- WHO Food Additives Series 24
- JECFA Evaluation: Arsenic
- Arsenic trisulfide
Шаблон:Arsenic compounds Шаблон:Sulfides
- ↑ Wells, A.F. (1984). Structural Inorganic Chemistry, Oxford: Clarendon Press. Шаблон:ISBN.
- ↑ Arsenic sulfide (As2S3)
- ↑ Шаблон:Cite journal
- ↑ Шаблон:Cite journal
- ↑ Шаблон:Cite journal
- ↑ Шаблон:Cite journal
- ↑ Шаблон:Cite journal
- ↑ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. Шаблон:ISBN.
- ↑ Шаблон:Cite journal
- ↑ Шаблон:Cite journal
- ↑ Шаблон:Cite journal
- ↑ Zenkin, S. A.; Mamedov, S. B.; Mikhailov, M. D.; Turkina, E. Yu.; Yusupov, I. Yu. Glass Phys. Chem. 1997, 5, pp 393-399.
- ↑ Material Safety Data Sheet Шаблон:Webarchive
- ↑ Linping Kuai, Arjun A. Nair, and Martin F. Polz "Rapid and Simple Method for the Most-Probable-Number Estimation of Arsenic-Reducing Bacteria" Appl Environ Microbiol. 2001, vol. 67, 3168–3173. Шаблон:Doi.
