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Ammonium thiocyanate

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Ammonium thiocyanate
Space-filling model of the ammonium cation
Space-filling model of the ammonium cation
Space-filling model of the thiocyanate anion
Space-filling model of the thiocyanate anion
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.015.614 Edit this at Wikidata
RTECS number
  • XN6465000
  • InChI=1S/CHNS.H3N/c2-1-3;/h3H;1H3 ☒N
    Key: SOIFLUNRINLCBN-UHFFFAOYSA-N ☒N
  • InChI=1/CHNS.H3N/c2-1-3;/h3H;1H3
    Key: SOIFLUNRINLCBN-UHFFFAOYAF
  • [S-]C#N.[NH4+]
Properties
NH4SCN
Molar mass 76.122 g/mol
Appearance Colorless hygroscopic crystalline solid
Density 1.305 g/cm3
Melting point 149.5 °C (301.1 °F; 422.6 K)
Boiling point 170 °C (338 °F; 443 K) (decomposes)
128 g/100 mL (0 °C)
Solubility soluble in liquid ammonia, alcohol, acetone
-48.1·10−6 cm3/mol
Hazards
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformFlammability 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilInstability 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g. calciumSpecial hazards (white): no code
2
1
1
Safety data sheet (SDS) External MSDS
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)

Ammonium thiocyanate is an inorganic compound with the formula NH4SCN. It is the salt of the ammonium cation and the thiocyanate anion.

Uses

Ammonium thiocyanate is used in the manufacture of herbicides, thiourea, and transparent artificial resins; in matches; as a stabilizing agent in photography; in various rustproofing compositions; as an adjuvant in textile dyeing and printing; as a tracer in oil fields; in the separation of hafnium from zirconium, and in titrimetric analyses.

Ammonium thiocyanate can also be used to determine the iron content in soft drinks by colorimetry.

Preparation

Ammonium thiocyanate is made by the reaction of carbon disulfide with aqueous ammonia. Ammonium dithiocarbamate is formed as an intermediate in this reaction, which upon heating, decomposes to ammonium thiocyanate and hydrogen sulfide:

CS2 + 2 NH3(aq) → NH2C(=S)SNH4 → NH4SCN + H2S

Reactions

Ammonium thiocyanate is stable in air; however, upon heating it isomerizes to thiourea:

The equilibrium mixtures at 150 °C and 180 °C contain 30.3% and 25.3% (by weight) thiourea, respectively. When heated at 200 °C, the dry powder decomposes to ammonia, hydrogen sulfide, and carbon disulfide, leaving a residue of guanidinium thiocyanate.

NH4SCN is weakly acidic; reacts with caustic soda or caustic potash to form sodium thiocyanate or potassium thiocyanate. It reacts with ferric salts to form a deep-red ferric thiocyanate complex:

6 SCN− + Fe3+ → [Fe(SCN)6]3−

Ammonium thiocyanate reacts with several metal ions including copper, silver, zinc, lead, and mercury, forming their thiocyanate precipitates, which may be extracted into organic solvents.

References

  1. A. F. Wells, Structural Inorganic Chemistry, 5th ed., Oxford University Press, Oxford, UK, 1984. ISBN 978-0198553700
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