Ammonium thiocyanate

Ammonium thiocyanate
Space-filling model of the ammonium cation	Space-filling model of the thiocyanate anion
Identifiers
CAS Number	1762-95-4 ;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:231858;
ChemSpider	14901 ;
ECHA InfoCard	100.015.614
EC Number	217-175-6;
PubChem CID	15666;
RTECS number	XN6465000;
UNII	YYL9152Z1Y ;
UN number	3077
CompTox Dashboard (EPA)	DTXSID3029653 ;
	InChI InChI=1S/CHNS.H3N/c2-1-3;/h3H;1H3 Key: SOIFLUNRINLCBN-UHFFFAOYSA-N ; InChI=1/CHNS.H3N/c2-1-3;/h3H;1H3 Key: SOIFLUNRINLCBN-UHFFFAOYAF;
	SMILES [S-]C#N.[NH4+];
Properties
Chemical formula	[NH4][SCN]
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)
Solubility in water	128 g/(100 mL) (0 °C)
Solubility	soluble in liquid ammonia, alcohol, acetone
Magnetic susceptibility (χ)	−48.1·10−6 cm3/mol
Hazards
	GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H302, H312, H332, H410, H412
Precautionary statements	P261, P264, P270, P271, P273, P280, P301+P312, P302+P352, P304+P312, P304+P340, P312, P322, P330, P363, P391, P501
NFPA 704 (fire diamond)	2 1 1
Safety data sheet (SDS)	External MSDS
Related compounds
Other anions	Ammonium cyanate
Other cations	Guanidinium thiocyanate; Lithium thiocyanate; Sodium thiocyanate; Potassium thiocyanate; Barium thiocyanate; Cobalt(II) thiocyanate; Copper(I) thiocyanate; Copper(II) thiocyanate; Silver thiocyanate; Mercury(II) thiocyanate; Lead(II) thiocyanate;
Related compounds	Ammonium cyanide
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Ammonium thiocyanate is an inorganic compound with the formula [NH₄]⁺[SCN]⁻. It is an ammonium salt of thiocyanic acid. It consists of ammonium cations [NH₄]⁺ and thiocyanate anions [SCN]⁻.

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 (important for the production of hafnium-free zircalloy for use in nuclear fuel cladding), and in titrimetric analyses.

In May 1945, USAAF General Victor E. Betrandias advanced a proposal to his superior General Arnold to use of ammonium thiocyanate to reduce rice crops in Japan as part of the bombing raids on their country.^[1]

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

Ammonium thiocyanate may also be used to separate quinidine, from liquors, after the isolation of quinine from the neutral, aqueous, sulphate solution. The salt is added to the hot solution and the gummy solid that forms is strained off from the liquid. The solid is then refluxed with methanol, which dissolves most of the impurities, leaving the quinidine thiocyanate as a crystalline solid of 90 - 95% purity. Following separation, (usually by centrifuge) the solid may then be further purified to pharmaceutical quality. (Quinidine is used for the treatment of heart arrhythmia and therefore has considerable value.)

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) → [NH₂−CS₂]⁻[NH₄]⁺ → [NH₄]⁺[SCN]⁻ + 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.

[NH₄]⁺[SCN]⁻ is weakly acidic due to the ammonium ion; it reacts with alkali hydroxides, such as sodium hydroxide or potassium hydroxide to form sodium thiocyanate or potassium thiocyanate, along with water and ammonia. The thiocyanate anion, specifically, 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

^ John David Chappell (1997). Before the Bomb: How America Approached the End of the Pacific War. University Press of Kentucky. pp. 91–92. ISBN 978-0-8131-7052-7.

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

[Chappell1997-1] John David Chappell (1997). Before the Bomb: How America Approached the End of the Pacific War. University Press of Kentucky. pp. 91–92. ISBN 978-0-8131-7052-7.

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