Silver thiocyanate

Silver thiocyanate is the silver salt of thiocyanic acid with the formula AgSCN. Silver thiocyanate appears as a white crystalline powder. It is very commonly used in the synthesis of silver nanoparticles. Additionally, studies have found silver nanoparticles to be present in saliva present during the entire digestive process of silver nitrate. Silver thiocyanate is slightly soluble in water, with a solubility of 1.68 x 10⁻⁴ g/L.^[6] It is insoluble in ethanol, acetone, and acid.^[7]

Silver thiocyanate

Skeletal formula of silver thiocyanate
Ball-and-stick model of silver thiocyanate
Names
IUPAC name Silver(I) thiocyanate, Silver thiocyanate
Other names Thiocyanic acid, silver (1+) thiocyanate; Silver isothiocyanate; Silver sulphocyanide[1]
Identifiers
CAS Number	1701-93-5 Y
3D model (JSmol)	Interactive image
ChemSpider	66941 Y
ECHA InfoCard	100.015.395
EC Number	216-934-9
PubChem CID	74345
UNII	S44O8TME5U Y
UN number	3077
CompTox Dashboard (EPA)	DTXSID30883742
InChI InChI=1S/CHNS.Ag/c2-1-3;/h3H;/q;+1/p-1 Y[inchi] Key: RHUVFRWZKMEWNS-UHFFFAOYSA-M Y[inchi]
SMILES C(#N)[S-].[Ag+]
Properties
Chemical formula	AgSCN
Appearance	Colorless crystals
Odor	Odorless
Melting point	170 °C (338 °F; 443 K) decomposes[2]
Solubility in water	0.14 mg/L (19.96 °C) 0.25 mg/L (21 °C) 6.68 mg/L (100 °C)[1]
Solubility product (Ksp)	1.03·10−12[3]
Solubility	Insoluble in acids (reacts)[4] except when concentrated, acetates, aq. nitrates[1]
Solubility in silver nitrate	43.2 mg/L (25.2 °C, 3 nAgNO3/H2O)[1]
Solubility in sulfur dioxide	14 mg/kg (0 °C)[2]
Solubility in methanol	0.0022 mg/kg[2]
Magnetic susceptibility (χ)	−6.18·10−5 cm3/mol[3]
Structure
Crystal structure	Monoclinic, mS32 (293 K)[5]
Space group	C2/c, No. 15 (293 K)[5]
Point group	2/m (293 K)[5]
Lattice constant	a = 8.792(5) Å, b = 7.998(5) Å, c = 8.207(5) Å (293 K)[5] α = 90°, β = 93.75(1)°, γ = 90°
Formula units (Z)	8
Thermochemistry
Heat capacity (C)	63 J/mol·K[2]
Std molar entropy (S⦵298)	131 J/mol·K[2]
Std enthalpy of formation (ΔfH⦵298)	88 kJ/mol[2]
Hazards
GHS labelling:
Pictograms	[4]
Signal word	Warning
Hazard statements	H302, H312, H332, H410[4]
Precautionary statements	P273, P280, P501[4]
NFPA 704 (fire diamond)	2 0 0
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Structure

AgSCN is monoclinic with 8 molecules per unit cell. Each SCN⁻ group has an almost linear molecular geometry, with bond angle 179.6(5)°. Weak Ag—Ag interactions of length 0.3249(2) nm to 0.3338(2) nm are present in the structure.^[5]

Production

Solution reaction

Silver thiocyanate has been commonly produced by the reaction between silver nitrate and potassium thiocyanate.^{[citation needed]}

AgNO₃ + KSCN → KNO₃ + AgSCN

Ion-exchange route

Silver thiocyanate may be formed via an ion exchange reaction. In this double displacement reaction, silver nitrate and ammonium thiocyanate are dissolved in distilled water to produce silver thiocyanate and ammonium nitrate.^[8]

AgNO₃ + NH₄SCN → NH₄NO₃ + AgSCN

Additionally, silver thiocyanate can be formed through the double displacement reaction between ammonium thiocyanate and silver chloride to form a precipitate of silver thiocyanate.

AgCl + NH₄SCN → NH₄Cl + AgSCN

Uses

The most common use of silver thiocyanate is as a silver nanoparticle. Silver thiocyanate nanoparticles have been found in saliva throughout the entire artificial digestion of silver nitrate.^[9] The nanoparticles can also be used as good ion conductors.^[10]

Silver thiocyanate has also been used to absorb uv-visible light at values less than 500 nm. At longer wavelengths, silver thiocyanate has been found to have good photocatalytic properties.^[8]

Characterization

Upon production, silver thiocyanate can be characterized through a wide range of techniques: x-ray powder diffraction (XRD), x-ray photoelectron spectroscopy (XPS), Raman Spectroscopy, ultraviolet photoelectron spectroscopy (UPS), and thermogravimetric analysis (TGA).^{[citation needed]}