Sodium cyanide

Last updated
Sodium cyanide
Sodium cyanide bonding Sodium cyanide.svg
Sodium cyanide bonding
Sodium-cyanide-phase-I-unit-cell-3D-SF.png
Identifiers
3D model (JSmol)
ChEMBL
ChemSpider
ECHA InfoCard 100.005.091 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 205-599-4
PubChem CID
RTECS number
  • VZ7525000
UNII
UN number 1689
  • InChI=1S/CN.Na/c1-2;/q-1;+1 Yes check.svgY
    Key: MNWBNISUBARLIT-UHFFFAOYSA-N Yes check.svgY
  • InChI=1S/CN.Na/c1-2;/q-1;+1
    Key: MNWBNISUBARLIT-UHFFFAOYAG
  • [C-]#N.[Na+]
Properties
NaCN
Molar mass 49.0072 g/mol
Appearancewhite solid
Odor faint bitter almond-like
Density 1.5955 g/cm3
Melting point 563.7 °C (1,046.7 °F; 836.9 K)
Boiling point 1,496 °C (2,725 °F; 1,769 K)
48.15 g/100 mL (10 °C)
63.7 g/100 mL (25 °C)
Solubility soluble in ammonia, methanol, ethanol
very slightly soluble in dimethylformamide, SO2
insoluble in dimethyl sulfoxide
1.452
Thermochemistry [1]
70.4 J·mol−1·K−1
Std molar
entropy (S⦵298)
115.6 J·mol−1·K−1
−87.5 kJ·mol−1
−76.4 kJ·mol−1
Enthalpy of fusion (ΔfH⦵fus)
8.79 kJ·mol−1
Hazards
GHS labelling:
GHS-pictogram-skull.svg GHS-pictogram-pollu.svg
NFPA 704 (fire diamond)
NFPA 704.svgHealth 4: Very short exposure could cause death or major residual injury. E.g. VX gasFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
4
0
0
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
4 mg/kg (sheep, oral)
15 mg/kg (mammal, oral)
8 mg/kg (rat, oral) [2]
NIOSH (US health exposure limits):
PEL (Permissible)
TWA 5 mg/m3 [3]
REL (Recommended)
C 5 mg/m3 (4.7 ppm) [10-minute] [3]
IDLH (Immediate danger)
25 mg/m3 (as CN) [3]
Safety data sheet (SDS) ICSC 1118
Related compounds
Other cations
Potassium cyanide
Related compounds
 Hydrogen cyanide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

Sodium cyanide is a compound with the formula Na C N and the structure Na+− C≡N . It is a white, water-soluble solid. Cyanide has a high affinity for metals, which leads to the high toxicity of this salt. Its main application, in gold mining, also exploits its high reactivity toward metals. It is a moderately strong base.

Contents

Production and chemical properties

Sodium cyanide is produced by treating hydrogen cyanide with sodium hydroxide: [4]

HCN + NaOH → NaCN + H2O

Worldwide production was estimated at 500,000 tons in the year 2006. Formerly it was prepared by the Castner process involving the reaction of sodium amide with carbon at elevated temperatures.

NaNH2 + C → NaCN + H2

The structure of solid NaCN is related to that of sodium chloride. [5] The anions and cations are each six-coordinate. Potassium cyanide (KCN) adopts a similar structure. [6]

When treated with acid, it forms the toxic gas hydrogen cyanide:

NaCN + H+ → HCN + Na+

Because the salt is derived from a weak acid, sodium cyanide readily reverts to HCN by hydrolysis; the moist solid emits small amounts of hydrogen cyanide, which is thought to smell like bitter almonds (not everyone can smell it—the ability thereof is due to a genetic trait [7] ). Sodium cyanide reacts rapidly with strong acids to release hydrogen cyanide. This dangerous process represents a significant risk associated with cyanide salts. It is detoxified most efficiently with hydrogen peroxide (H2O2) to produce sodium cyanate (NaOCN) and water: [4]

NaCN + H2O2 → NaOCN + H2O

Applications

Cyanide mining

Gold cyanidation (also known as the cyanide process) is the dominant technique for extracting gold, much of which is obtained from low-grade ore. More than 70% of cyanide consumption globally is used for this purpose. The application exploits the high affinity of gold(I) for cyanide, which induces gold metal to oxidize and dissolve in the presence of air (oxygen) and water, producing the salt sodium dicyanoaurate (or sodium gold cyanide) (NaAu(CN)2): [4]

4 Au + 8 NaCN + O2 + 2 H2O → 4 Na[Au(CN)2] + 4 NaOH

A similar process uses potassium cyanide (KCN, a close relative of sodium cyanide) to produce potassium dicyanoaurate (KAu(CN)2). The

These soluble forms of gold (and silver) can be converted back to the metals by electrolysis.

Chemical feedstock

Some commercially significant chemicals are derived from cyanide: cyanuric chloride, cyanogen chloride, and cyanogen. [4]

Several specialty nitriles may be produced by alkylation of cyanide, a strong nucleophile. Illustrative is the synthesis of benzyl cyanide by the reaction of benzyl chloride and sodium cyanide: [8]

C6H5CH2Cl + NaCN → C6H5CH2CN + NaCl

Electroplating

Cyanide baths (solutions) of metal ions are used to electroplate many metals, including platinum, gold, and silver. Cadmium plating gives excellent corrosion resistance and is achieved using cadmium oxide and sodium cyanide. [9] Copper 'strikes' (thin high quality layers) are traditionally formed using cyanide electroplating, these thin interstitial layers allow adhesion between metals that are usually incompatible, such as chromium and aluminium.[ citation needed ]

Niche uses

Being highly toxic, sodium cyanide is used to kill or stun rapidly such as in collecting jars used by entomologists and in widely illegal cyanide fishing.

It was used as an insecticide, rodenticide and antibacterial, but these uses were cancelled by the EPA in 1987. [10]

Toxicity

Sodium cyanide, like other soluble cyanide salts, is among the most rapidly acting of all known poisons. NaCN is a potent inhibitor of respiration, acting on mitochondrial cytochrome oxidase and hence blocking electron transport. This results in decreased oxidative metabolism and oxygen utilization. Lactic acidosis then occurs as a consequence of anaerobic metabolism. An oral dosage as small as 200–300 mg can be fatal.

Disposal

Due to toxicity considerations, the disposal of cyanide is subject to stringent regulations. Industrial cyanide effluent is typically destroyed by oxidation using peroxysulfuric acid, hydrogen peroxide, sulfur dioxide/copper salts ("Inco process") or all three ("Combiox Process"). Use of sodium hypochlorite, traditional for laboratory-scale wastes, is impractical on a commercial scale. Hydrolysis at higher temperatures is highly effective, but requires specialized equipment. Lastly, cyanide wastes can be acidified for recovery of hydrogen cyanide. [4]

References

  1. ↑ CRC handbook of chemistry and physics : a ready-reference book of chemical and physical data. William M. Haynes, David R. Lide, Thomas J. Bruno (2016-2017, 97th ed.). Boca Raton, Florida. 2016. ISBN   978-1-4987-5428-6. OCLC   930681942.{{cite book}}: CS1 maint: location missing publisher (link) CS1 maint: others (link)
  2. ↑ "Cyanides (as CN)". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  3. 1 2 3 NIOSH Pocket Guide to Chemical Hazards. "#0562". National Institute for Occupational Safety and Health (NIOSH).
  4. 1 2 3 4 5 Gail, Ernst; Gos, Stephen; Kulzer, Rupprecht; Lorösch, Jürgen; Rubo, Andreas; Sauer, Manfred; Kellens, Raf; Reddy, Jay; Steier, Norbert; Hasenpusch, Wolfgang (2011). "Cyano Compounds, Inorganic". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a08_159.pub3. ISBN   978-3-527-30385-4.
  5. ↑ Wells, A.F. (1984) Structural Inorganic Chemistry, Oxford: Clarendon Press. ISBN   0-19-855370-6.
  6. ↑ H. T. Stokes; D. L. Decker; H. M. Nelson; J. D. Jorgensen (1993). "Structure of potassium cyanide at low temperature and high pressure determined by neutron diffraction". Phys. Rev. B (Submitted manuscript). 47 (17): 11082–11092. Bibcode:1993PhRvB..4711082S. doi:10.1103/PhysRevB.47.11082. PMID   10005242.
  7. ↑ Online Mendelian Inheritance in Man (OMIM): 304300
  8. ↑ Adams, Roger; Thal, A. F. (1922). "Benzyl cyanide". Organic Syntheses. 2: 9. doi:10.15227/orgsyn.002.0009.
  9. ↑ Schulte-Schrepping, Karl-Heinz; Piscator, Magnus (2000). "Cadmium and Cadmium Compounds". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a04_499. ISBN   978-3-527-30385-4.
  10. ↑ "Reregistration Eligibility Decision (R.E.D. Facts) Sodium cyanide" (PDF). United States Environmental Protection Agency. September 1994.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.