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Silver Sulfide

Silver sulfide represented by the chemical formula Ag2S [1] is a black crystalline powder that is soluble in nitric acid, sulfuric acid and alkali cyanide solutions. Ag2S is insoluble in alcohol [1, 5]. It occurs in nature as the mineral argentite and is an ionic compound [5, 6]. It is very stable and doesn’t decompose easily except at an extremely high temperature or by the electrolysis of the molten compound [11].

Silver Sulfide

Silver Sulfide Identification

CAS Number 21548-73-2 [1]
PubChem CID 30686 [2]
ChemSpider ID 145878 [3]
EC Number 244-438-2 [1]

Composition and Synthesis

Silver sulfide can be prepared by a reaction between silver and gaseous hydrogen sulfide. Hydrogen gas is released in the process.

2Ag + H2S = Ag2S + H2

Our silverware tarnishes because of the above reaction. Air contains traces of hydrogen sulfide which causes the silver to tarnish forming silver sulfide. You can polish your silver utensils clean by rubbing them with a cloth and polishing compounds [7] It can be represented by the below reaction with aluminum that involves the reduction of silver sulfide to silver [13].

3Ag2S + 2Al = 6Ag + Al2S3

Silver Sulfide Formula

Properties and Characteristics of Silver Sulfide

General Properties

Molar mass/molecular weight 248.804 g/mol [2]

Physical Properties

Color/appearance Black powder [1]
Melting point/freezing point 845°C, 1553°F [1]
Boiling point N/A [1]
Density 7.234 g cm-3 [1]
State of matter at room temperature (normal phase) Solid [1]
Resistivity 0.1 – 10 ohm-m [14]

Chemical Properties

Solubility in water Insoluble [5]
pH <7 (acidic) [6]

Atomic Properties

Crystal structure Orthogonal [4]
Band gap of nanoparticles 0.96 eV [10]

Silver Sulfide Structure

Prominent Reactions

Silver sulfide reacts with hydrochloric acid to produce silver chloride and hydrogen sulfide [9].

Ag2S + 2HCl = 2AgCl + H2S

It reacts with nitric acid to form silver sulfate, nitric oxide and water [8].

3Ag2S + 8HNO3 = 3Ag2SO4 + 8NO + 4H2O

Silver Sulfide Uses

  1. The compound finds application in anti-microbial and anti-bacterial agents [4].
  2. As a photosensitizer in photography [4].
  3. As a lab reagent [4].
  4. Inlaying in niello metalwork and ceramics [5].

Is It Dangerous

The compound is irritating to the eyes, skin and respiratory system. Hence contact and inhalation should be avoided [4]. Ingestion is harmful as it may cause health hazards like irreversible pigmentation during metabolism [12].

Silver Sulfide (Ag2S) Price

5 gram of the compound costs around $80 [8].


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  2. Disilver Sulphide –
  3. Silver Sulfide –
  4. Silver sulfide (Ag2S) semiconductors –
  5. Silver (I) Sulfide –
  6. Is Silver Sulfide An Acid or Base? –
  7. What is Silver Sulfide? – Chemical Formula & Uses –
  8. Silver (I) Sulfide –
  9. Silver sulfide hydrochloric acid ag 2 s 2hcl 2agcl h –
  10. The structural and optical constants of Ag2S semiconductor nanostructure in the Far-Infrared –
  11. Chemical decomposition of silver sulfide? –
  12. Exposure-Related Health Effects of Silver and Silver Compounds: A Review –
  13. Finishing techniques in metalwork –
  14. Silver and sulfur: case studies, physics and possible solutions-

2 responses to “Silver Sulfide”

  1. Shub says:

    Ag2S + 2HCl = 2AgCl + H2S

    How can this reaction take place despite silver being less reactive than hydrogen in the reactivity series?

    • Satyam Bhuyan says:

      Silver alone cannot displace hydrogen from hydrochloric acid, but silver sulfide can. So, this reaction is possible.

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