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| Identifiers | |
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3D model (JSmol) | |
| ChEMBL | |
| ChemSpider |
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| ECHA InfoCard | 100.005.091 |
| EC Number |
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| RTECS number |
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| UNII | |
| UN number | 1689 |
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| Properties | |
| NaCN | |
| Molar mass | 49.0072 g/mol |
| Appearance | white solid |
| Odor | faintbitter 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 inammonia,methanol,ethanol very slightly soluble indimethylformamide,SO2 insoluble indimethyl sulfoxide |
Refractive index (nD) | 1.452 |
| Thermochemistry[1] | |
| 70.4 J·mol−1·K−1 | |
Std molar entropy(S⦵298) | 115.6 J·mol−1·K−1 |
Std enthalpy of formation(ΔfH⦵298) | −87.5 kJ·mol−1 |
Gibbs free energy(ΔfG⦵) | −76.4 kJ·mol−1 |
Enthalpy of fusion(ΔfH⦵fus) | 8.79 kJ·mol−1 |
| Hazards | |
| GHS labelling: | |
  | |
| NFPA 704 (fire diamond) | |
| Flash point | Non-flammable |
| Lethal dose or concentration (LD, LC): | |
LD50 (median dose) | 4 mg/kg (sheep, oral) 15 mg/kg (mammal, oral) 8 mg/kg (rat, oral)[3] |
| NIOSH (US health exposure limits): | |
PEL (Permissible) | TWA 5 mg/m3[2] |
REL (Recommended) | C 5 mg/m3 (4.7 ppm) [10-minute][2] |
IDLH (Immediate danger) | 25 mg/m3 (as CN)[2] |
| Safety data sheet (SDS) | ICSC 1118 |
| Related compounds | |
Othercations | Potassium cyanide |
Related compounds | Hydrogen cyanide |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Sodium cyanide is acompound with theformulaNaCN and thestructureNa+−C≡N. It is a white,water-soluble solid.Cyanide has a high affinity for metals, which leads to the hightoxicity of thissalt. Its main application, ingold mining, also exploits its high reactivity toward metals. It is amoderately strong base.
Sodium cyanide is produced by treatinghydrogen cyanide withsodium hydroxide:[4]
Worldwide production was estimated at 500,000 tons in the year 2006. Formerly it was prepared by the Castner process involving the reaction ofsodium amide with carbon at elevated temperatures.
The structure of solid NaCN is related to that ofsodium chloride.[5] The anions and cations are each six-coordinate.Potassium cyanide (KCN) adopts a similar structure.[6]
When treated withacid, it forms the toxic gashydrogen cyanide:
Because the salt is derived from a weak acid, sodium cyanide readily reverts to HCN byhydrolysis; the moist solid emits small amounts of hydrogen cyanide, which is thought to smell like bitteralmonds (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 withhydrogen peroxide (H2O2) to producesodium cyanate (NaOCN) and water:[4]
Gold cyanidation (also known as the cyanide process) is the dominant technique for extractinggold, much of which is obtained from low-gradeore. 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 saltsodium dicyanoaurate (or sodium gold cyanide) (NaAu(CN)2):[4]
A similar process usespotassium cyanide (KCN, a close relative of sodium cyanide) to producepotassium dicyanoaurate (KAu(CN)2).
These soluble forms of gold (and silver) can be converted back to the metals by electrolysis.
Some commercially significant chemicals are derived from cyanide:cyanuric chloride,cyanogen chloride, andcyanogen.[4]
Several specialtynitriles may be produced by alkylation of cyanide, a strongnucleophile. Illustrative is the synthesis ofbenzyl cyanide by the reaction ofbenzyl chloride and sodium cyanide:[8]
Cyanide baths (solutions) of metal ions are used toelectroplate many metals, includingplatinum, gold, and silver.Cadmium plating gives excellent corrosion resistance and is achieved usingcadmium 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]
Being highly toxic, sodium cyanide is used to kill or stun rapidly such as in collecting jars used byentomologists and in widely illegalcyanide fishing.
It was used as aninsecticide,rodenticide andantibacterial, but these uses were cancelled by theEPA in 1987.[10]
Sodium cyanide, like other soluble cyanide salts, is among the most rapidly acting of all known poisons. NaCN is a potent inhibitor of cellularrespiration, acting on mitochondrialcytochrome 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.
Due to toxicity considerations, the disposal of cyanide is subject to stringent regulations. Industrial cyanide effluent is typically destroyed by oxidation usingperoxysulfuric acid,hydrogen peroxide,sulfur dioxide/copper salts ("Inco process") or all three ("Combiox Process"). Use ofsodium 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 ofhydrogen cyanide.[4]
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