Mercury(II) thiocyanate
Names | |
---|---|
Other names
Mercuric thiocyanate
Mercuric sulfocyanate | |
Identifiers | |
3D model (
JSmol ) |
|
ECHA InfoCard
|
100.008.886 |
EC Number |
|
PubChem CID
|
|
UNII | |
CompTox Dashboard (EPA)
|
|
| |
| |
Properties | |
Hg(SCN)2 | |
Molar mass | 316.755 g/mol |
Appearance | White monoclinic powder
|
Odor | odorless |
Density | 3.71 g/cm3, solid |
Melting point | 165 °C (329 °F; 438 K) (decomposes) |
0.069 g/100 mL | |
Solubility | Soluble in dilute hydrochloric acid, KCN, ammonia slightly soluble in alcohol, ether |
−96.5·10−6 cm3/mol | |
Hazards | |
Occupational safety and health (OHS/OSH): | |
Main hazards
|
highly toxic |
GHS labelling:[1] | |
Danger | |
H300, H310, H330, H373, H410 | |
P260, P262, P270, P271, P273, P280, P284, P301+P316, P302+P352, P304+P340, P316, P319, P320, P321, P330, P361, P364, P391, P403+P233, P405, P501 | |
NFPA 704 (fire diamond) | |
Lethal dose or concentration (LD, LC): | |
LD50 (median dose)
|
46 mg/kg (rat, oral) |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|
Mercury(II) thiocyanate (Hg(SCN)2) is an inorganic
Synthesis and structure
The first synthesis of mercury thiocyanate was probably completed in 1821 by Jöns Jacob Berzelius:
- HgO + 2 HSCN → Hg(SCN)2 + H2O
Evidence for the first pure sample was presented in 1866 prepared by a chemist named Otto Hermes.
- Hg(NO3)2 + 2 KSCN → Hg(SCN)2 + 2KNO3
The compound adopts a polymeric structure with Hg2+ centres linearly coordinated to two S atoms with a distance of 2.381 Å. Four weak Hg2+--N interactions are indicated with distances of 2.81 Å.[4]
Uses
Mercury thiocyanate has a few uses in chemical synthesis. It is the precursor to other
Its reactions with organic halides yield two products, one with the sulfur bound to the organic compound and one with the nitrogen bound to the organic compound.[6]
Use in chloride analysis
It was discovered that mercury thiocyanate can improve detection limits in the determination of chloride ions in water by
It can determine the concentration of chloride ions in an aqueous solution. Mercury thiocyanate without iron (III) is added to a solution with an unknown concentration of chloride ions, forming a complex of the mercury thiocyanate and chloride ion that absorbs light at a 254 nm, allowing more accurate measurements of attention than the aforementioned technique using the iron.[7]
Pharaoh's serpent
Mercury thiocyanate was formerly used in pyrotechnics causing an effect known as the Pharaoh's serpent or Pharaoh's snake. When the compound is in the presence of a strong enough heat source, a rapid, exothermic reaction that produces a large mass of coiling, serpent-like solid is started. An inconspicuous flame, which is often blue but can also be yellow/orange, accompanies the combustion. The resulting solid can range from dark graphite gray to light tan in colour with the inside generally much darker than the outside.[2]
The reaction has several stages as follows:[8] Igniting mercury thiocyanate causes it to form an insoluble brown mass that is primarily carbon nitride, C3N4. Mercury sulfide and carbon disulfide are also produced.
References
- ^ "Mercuric thiocyanate (Compound)". pubchem.ncbi.nlm.nih.gov. Retrieved 31 May 2023.
- ^ .
- .
- doi:10.1139/v72-153
- .
- .
- ^ .
- ^ "Make a Pharaoh's Snake Firework". About.com Education. Archived from the original on 2012-02-01. Retrieved 2016-02-08.
External links
- "Pharaoh's snake". YouTube. September 2, 2008.
- "How to make the Pharaoh's Serpent (Mercury (II) Thiocyanate)". YouTube. March 24, 2014