Silver sulfide
Names | |
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IUPAC name
Silver(I) sulfide
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Other names
Silver sulfide
Argentous sulfide | |
Identifiers | |
3D model (
JSmol ) |
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ChemSpider | |
ECHA InfoCard
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100.040.384 |
EC Number |
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PubChem CID
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UNII | |
CompTox Dashboard (EPA)
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Properties | |
Ag2S | |
Molar mass | 247.80 g·mol−1 |
Appearance | Grayish-blackish crystal |
Odor | Odorless |
Density | 7.234 g/cm3 (25 °C)[1][2] 7.12 g/cm3 (117 °C)[3] |
Melting point | 836 °C (1,537 °F; 1,109 K)[1] |
6.21·10−15 g/L (25 °C) | |
Solubility product (Ksp)
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6.31·10−50 |
Solubility | Soluble in aq. HCN, aq. citric acid with KNO3 Insoluble in acids, alkalies, aqueous ammoniums[4] |
Structure | |
Cubic, cI8 (α-form) Monoclinic, mP12 (β-form) Cubic, cF12 (γ-form)[3][5] | |
Im3m, No. 229 (α-form)[5] P21/n, No. 14 (β-form) Fm3m, No. 225 (γ-form)[3] | |
2/m (α-form)[5] 4/m 3 2/m (β-form, γ-form)[3] | |
a = 4.23 Å, b = 6.91 Å, c = 7.87 Å (α-form)[5] α = 90°, β = 99.583°, γ = 90°
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Thermochemistry | |
Heat capacity (C)
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76.57 J/mol·K[6] |
Std molar
entropy (S⦵298) |
143.93 J/mol·K[6] |
Std enthalpy of (ΔfH⦵298)formation |
−32.59 kJ/mol[6] |
Gibbs free energy (ΔfG⦵)
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−40.71 kJ/mol[6] |
Hazards | |
Occupational safety and health (OHS/OSH): | |
Main hazards
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May cause irritation |
GHS labelling: | |
[2] | |
Warning | |
H315, H319, H335[2] | |
P261, P305+P351+P338[2] | |
NFPA 704 (fire diamond) | |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Silver sulfide is an inorganic compound with the formula Ag
2S. A dense black solid, it is the only sulfide of silver. It is useful as a photosensitizer in photography. It constitutes the tarnish that forms over time on silverware and other silver objects. Silver sulfide is insoluble in most solvents, but is degraded by strong acids. Silver sulfide is a network solid made up of silver (electronegativity of 1.98) and sulfur (electronegativity of 2.58) where the bonds have low ionic character (approximately 10%).
Formation
Silver sulfide naturally occurs as the tarnish on silverware. When combined with silver, hydrogen sulfide gas creates a layer of black silver sulfide patina on the silver, protecting the inner silver from further conversion to silver sulfide.[8] Silver whiskers can form when silver sulfide forms on the surface of silver electrical contacts operating in an atmosphere rich in hydrogen sulfide and high humidity.[9] Such atmospheres can exist in sewage treatment and paper mills.[10][11]
Structure and properties
Three
History
In 1833 Michael Faraday noticed that the resistance of silver sulfide decreased dramatically as temperature increased. This constituted the first report of a semiconducting material.[13]
Silver sulfide is a component of classical qualitative inorganic analysis.[14]
References
- ^ ISBN 978-1-4200-9084-0.
- ^ a b c d Sigma-Aldrich Co., Silver sulfide. Retrieved on 2014-07-13.
- ^ ISBN 978-2-88124-761-3.
- ^ Comey, Arthur Messinger; Hahn, Dorothy A. (February 1921). A Dictionary of Chemical Solubilities: Inorganic (2nd ed.). New York: The MacMillan Company. p. 835.
- ^ ISBN 978-3-540-31360-1.
- ^ ISBN 978-0-07-049439-8.
- ^ "MSDS of Silver Sulfide". saltlakemetals.com. Utah, USA: Salt Lake Metals. Archived from the original on 2014-08-10. Retrieved 2014-07-13.
- ISBN 978-1-111-58065-0.
- ^ "Degradation of Power Contacts in Industrial Atmosphere: Silver Corrosion and Whiskers" (PDF). 2002.
- PMID 20163816.
- ^ "Control of Hydrogen Sulfide Generation | Water & Wastes Digest". www.wwdmag.com. 5 March 2012. Retrieved 2018-07-05.
- ^ Frueh, A. J. (1958). The crystallography of silver sulfide, Ag2S. Zeitschrift für Kristallographie-Crystalline Materials, 110(1-6), 136-144.
- ^ "1833 - First Semiconductor Effect is Recorded". Computer History Museum. Retrieved 24 June 2014.
- ISBN 978-0-08-037941-8.
External links
- Tarnishing of Silver: A Short Review V&A Conservation Journal
- Images of silver whiskers NASA