Silver sulfide
































































Silver sulfide (Ag
2S) is the sulfide of silver. It is useful as a photosensitizer in photography.




Contents





  • 1 Properties


  • 2 Miscellanea


  • 3 Structure


  • 4 References


  • 5 External links




Properties


This dense black solid constitutes the tarnish that forms over time on silverware and other silver objects.[8] Silver sulfide is insoluble in all 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%).



Miscellanea


  • It is a component of classical qualitative inorganic analysis.[9]

  • 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. [10]

  • 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.[11] Such atmospheres can exist in sewage treatment and paper mills.[12][13]


Structure


Three forms are known: monoclinic acanthite (β-form), stable below 179 °C, body centered cubic so-called argentite (α-form), stable above 180 °C, and a high temperature face-centred cubic (γ-form) stable above 586 °C.[5] The higher temperature forms are electrical conductors. It is found in nature as relatively low temperature mineral acanthite. Acanthite is an important ore of silver. In the acanthite, monoclinic, form there are two crystallographically distinct silver atoms with two and three near neighbour sulfur atoms respectively.[14] The name argentite refers to a cubic form, which, due to instability in "normal" temperatures, is found in form of the pseudomorphosis of acanthite after argentite.



References




  1. ^ ab Lide, David R., ed. (2009). CRC Handbook of Chemistry and Physics (90th ed.). Boca Raton, Florida: CRC Press. ISBN 978-1-4200-9084-0..mw-parser-output cite.citationfont-style:inherit.mw-parser-output qquotes:"""""""'""'".mw-parser-output code.cs1-codecolor:inherit;background:inherit;border:inherit;padding:inherit.mw-parser-output .cs1-lock-free abackground:url("//upload.wikimedia.org/wikipedia/commons/thumb/6/65/Lock-green.svg/9px-Lock-green.svg.png")no-repeat;background-position:right .1em center.mw-parser-output .cs1-lock-limited a,.mw-parser-output .cs1-lock-registration abackground:url("//upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Lock-gray-alt-2.svg/9px-Lock-gray-alt-2.svg.png")no-repeat;background-position:right .1em center.mw-parser-output .cs1-lock-subscription abackground:url("//upload.wikimedia.org/wikipedia/commons/thumb/a/aa/Lock-red-alt-2.svg/9px-Lock-red-alt-2.svg.png")no-repeat;background-position:right .1em center.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registrationcolor:#555.mw-parser-output .cs1-subscription span,.mw-parser-output .cs1-registration spanborder-bottom:1px dotted;cursor:help.mw-parser-output .cs1-hidden-errordisplay:none;font-size:100%.mw-parser-output .cs1-visible-errorfont-size:100%.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration,.mw-parser-output .cs1-formatfont-size:95%.mw-parser-output .cs1-kern-left,.mw-parser-output .cs1-kern-wl-leftpadding-left:0.2em.mw-parser-output .cs1-kern-right,.mw-parser-output .cs1-kern-wl-rightpadding-right:0.2em


  2. ^ abcd Sigma-Aldrich Co., Silver sulfide. Retrieved on 2014-07-13.


  3. ^ abcd Tonkov, E. Yu (1992). High Pressure Phase Transformations: A Handbook. 1. Gordon and Breach Science Publishers. p. 13. ISBN 2-88124-761-X.


  4. ^ Comey, Arthur Messinger; Hahn, Dorothy A. (February 1921). A Dictionary of Chemical Solubilities: Inorganic (2nd ed.). New York: The MacMillan Company. p. 835.


  5. ^ abcde "Silver sulfide (Ag2S) crystal structure". 41C. Springer Berlin Heidelberg. 1998: 1–4. doi:10.1007/10681727_86. ISBN 978-3-540-31360-1.


  6. ^ abcd Pradyot, Patnaik (2003). Handbook of Inorganic Chemicals. The McGraw-Hill Companies, Inc. p. 845. ISBN 0-07-049439-8.


  7. ^ "MSDS of Silver Sulfide". saltlakemetals.com. Utah, USA: Salt Lake Metals. Retrieved 2014-07-13.


  8. ^ "Silver". chemistryexplained.com. Advameg, Inc. Retrieved 2014-07-13.


  9. ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 0-08-037941-9.


  10. ^ Zumdahl, Steven S.; DeCoste, Donald J. (2013). Chemical Principles (7th ed.). p. 505. ISBN 978-1-111-58065-0.


  11. ^ "Degradation of Power Contacts in Industrial Atmosphere: Silver Corrosion and Whiskers" (PDF). 2002.


  12. ^ Dutta, Paritam K.; Rabaey, Korneel; Yuan, Zhiguo; Rozendal, René A.; Keller, Jürg (2010). "Electrochemical sulfide removal and recovery from paper mill anaerobic treatment effluent". Water Research. 44 (8): 2563–2571. doi:10.1016/j.watres.2010.01.008. ISSN 0043-1354.


  13. ^ "Control of Hydrogen Sulfide Generation | Water & Wastes Digest". www.wwdmag.com. Retrieved 2018-07-05.


  14. ^ FRUEH, A. J. (1958). The crystallography of silver sulfide, Ag2S. Zeitschrift für Kristallographie-Crystalline Materials, 110(1-6), 136-144.




External links



  • Tarnishing of Silver: A Short Review V&A Conservation Journal


  • Images of silver whiskers NASA

Silver sulfide

Ball-and-stick model of silver sulfide

Sample of silver sulfide
Names

IUPAC name
Silver(I) sulfide, Silver sulfide

Identifiers

CAS Number



  • 21548-73-2 ☑Y


3D model (JSmol)


  • Interactive image


ChemSpider


  • 145878 ☒N


ECHA InfoCard

100.040.384

EC Number
244-438-2


PubChem CID


  • 166738


UNII


  • 9ZB10YHC1C ☒N





Properties

Chemical formula


Ag2S

Molar mass
247.80 g·mol−1
Appearance
Grayish-black 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]

Solubility in water

6.21·10−15 g/L (25 °C)


Solubility product (Ksp)

6.31·10−50

Solubility
Soluble in aq. HCN, aq. citric acid with KNO3
Insoluble in acids, alkalies, aqueous ammoniums[4]
Structure

Crystal structure


Monoclinic, mP12 (β-form)
Cubic, cI8 (α-form)
Cubic, cF12 (γ-form)[3][5]

Space group

P21/n, No. 14 (α-form)[5]
Im3m, No. 229 (β-form)
Fm3m, No. 225 (γ-form)[3]

Point group

2/m (α-form)[5]
4/m 3 2/m (β-form, γ-form)[3]

Lattice constant



a = 4.23 Å, b = 6.91 Å, c = 7.87 Å (α-form)[5]

α = 90°, β = 99.583°, γ = 90°

Thermochemistry


Heat capacity (C)

76.57 J/mol·K[6]


Std molar
entropy (So298)

143.93 J/mol·K[6]


Std enthalpy of
formation (ΔfHo298)

−32.59 kJ/mol[6]


Gibbs free energy (ΔfG˚)

−40.71 kJ/mol[6]
Hazards
Main hazards
May cause irritation

GHS pictograms

The exclamation-mark pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)[2]

GHS signal word
Warning

GHS hazard statements


H315, H319, H335[2]

GHS precautionary statements


P261, P305+351+338[2]

NFPA 704


[7]



Flammability code 0: Will not burn. E.g., waterHealth code 0: Exposure under fire conditions would offer no hazard beyond that of ordinary combustible material. E.g., sodium chlorideReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogenSpecial hazards (white): no codeNFPA 704 four-colored diamond

0


0


0





Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).


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Infobox references










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