Calcium cyanide

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Calcium cyanide
Calcium cyanide structure.svg
Names
IUPAC name
calcium dicyanide
Systematic IUPAC name
calcium dicyanide
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.008.856 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 209-740-0
PubChem CID
UNII
  • InChI=1S/2CN.Ca/c2*1-2;/q2*-1;+2
  • [Ca+2].[C-]#N.[C-]#N
Properties
Ca(CN)2
Molar mass 92.1128 g/mol
Appearancewhite powder
Odor hydrogen cyanide
Density 1.853 (20 °C)
Melting point 640 °C (1,184 °F; 913 K) (decomposes)
soluble
Solubility soluble in alcohol, weak acids
Structure
rhombohedric
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
Highly Toxic
NFPA 704 (fire diamond)
3
0
1
Non-flammable
Lethal dose or concentration (LD, LC):
39 mg/kg rat, oral [1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Calcium cyanide is the inorganic compound with the formula Ca(CN)2. It is the calcium salt derived from hydrocyanic acid. It is a white solid, although the pure material is rarely encountered. It hydrolyses readily (even in moist air) to release hydrogen cyanide and is very toxic. [3]

Contents

Preparation

Solutions of calcium cyanide can be prepared by treating calcium hydroxide with hydrogen cyanide. Solid calcium cyanide is produced commercially by heating calcium cyanamide with sodium chloride. The reaction is incomplete. The product is only of 50% purity, other components being sodium cyanide, calcium cyanamide, and carbon. Because of the carbon impurity, the solid is black, hence material is often called black cyanide. [3]

Reactivity

At temperatures around 600 °C, calcium cyanide converts to calcium cyanamide: [4] [5]

Ca(CN)2 → CaCN2 + C

It is suspected that this reaction is one step in the conversion of calcium carbide with nitrogen gas. The ratio of calcium cyanide to calcium cyanamide is sensitive to the presence of alkali metal halides, such as sodium chloride.

Calcium cyanide hydrolyzes upon acidification to form hydrogen cyanide:

Ca(CN)2 + 2 H+ → Ca2+ + 2 HCN

Calcium cyanide reacts with ammonium carbonate to give produce ammonium cyanide:

Ca(CN)2 + (NH4)2CO3 → 2 NH4CN + CaCO3

Uses

Calcium cyanide is used almost exclusively in the mining industry. It serves as an inexpensive source of cyanide in many leaching or vat operation to obtain precious metals such as gold and silver from their ores. [3] [6]

Safety

Like other cyanide salts, this compound is highly toxic and its use is strictly regulated.

Related Research Articles

<span class="mw-page-title-main">Cyanide</span> Any chemical compound with cyanide anion

A cyanide is a chemical compound that contains a C≡N functional group. This group, known as the cyano group, consists of a carbon atom triple-bonded to a nitrogen atom.

In chemistry, a salt is a chemical compound consisting of an ionic assembly of positively charged cations and negatively charged anions, which results in a compound with no net electric charge. A common example is table salt, with positively charged sodium ions and negatively charged chloride ions.

Potassium ferrocyanide Chemical compound

Potassium ferrocyanide is the inorganic compound with formula K4[Fe(CN)6]·3H2O. It is the potassium salt of the coordination complex [Fe(CN)6]4−. This salt forms lemon-yellow monoclinic crystals.

Sodium cyanide Chemical compound

Sodium cyanide is a poisonous compound with the formula NaCN. 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.

<span class="mw-page-title-main">Potassium hydroxide</span> Inorganic compound with the formula KOH

Potassium hydroxide is an inorganic compound with the formula KOH, and is commonly called caustic potash.

A nitrile is any organic compound that has a −C≡N functional group. The prefix cyano- is used interchangeably with the term nitrile in industrial literature. Nitriles are found in many useful compounds, including methyl cyanoacrylate, used in super glue, and nitrile rubber, a nitrile-containing polymer used in latex-free laboratory and medical gloves. Nitrile rubber is also widely used as automotive and other seals since it is resistant to fuels and oils. Organic compounds containing multiple nitrile groups are known as cyanocarbons.

Formamide Chemical compound

Formamide is an amide derived from formic acid. It is a colorless liquid which is miscible with water and has an ammonia-like odor. It is chemical feedstock for the manufacture of sulfa drugs and other pharmaceuticals, herbicides and pesticides, and in the manufacture of hydrocyanic acid. It has been used as a softener for paper and fiber. It is a solvent for many ionic compounds. It has also been used as a solvent for resins and plasticizers. Some astrobiologists suggest that it may be an alternative to water as the main solvent in other forms of life.

Strontium chloride Chemical compound

Strontium chloride (SrCl2) is a salt of strontium and chlorine.

Calcium nitrate Chemical compound

Calcium nitrate, also called Norgessalpeter (Norwegian salpeter), is an inorganic compound with the formula Ca(NO3)2(H2O)x. The anhydrous compound, which is rarely encountered, absorbs moisture from the air to give the tetrahydrate. Both anhydrous and hydrated forms are colourless salts. Calcium nitrate is mainly used as a component in fertilizers, but it has other applications. Nitrocalcite is the name for a mineral which is a hydrated calcium nitrate that forms as an efflorescence where manure contacts concrete or limestone in a dry environment as in stables or caverns. A variety of related salts are known including calcium ammonium nitrate decahydrate and calcium potassium nitrate decahydrate.

Calcium sulfide Chemical compound of formula CaS

Calcium sulfide is the chemical compound with the formula CaS. This white material crystallizes in cubes like rock salt. CaS has been studied as a component in a process that would recycle gypsum, a product of flue-gas desulfurization. Like many salts containing sulfide ions, CaS typically has an odour of H2S, which results from small amount of this gas formed by hydrolysis of the salt.

Ammonium fluoride Chemical compound

Ammonium fluoride is the inorganic compound with the formula NH4F. It crystallizes as small colourless prisms, having a sharp saline taste, and is highly soluble in water. Like all fluoride salts, it is moderately toxic in both acute and chronic overdose.

Calcium cyanamide Chemical compound

Calcium cyanamide is the inorganic compound with the formula CaCN2. It is the calcium salt of the cyanamide (CN2−
2
) anion. This chemical is used as fertilizer and is commercially known as nitrolime. It was first synthesized in 1898 by Adolph Frank and Nikodem Caro (Frank–Caro process).

Potassium cyanate is an inorganic compound with the formula KOCN. It is a colourless solid. It is used to prepare many other compounds including useful herbicide. Worldwide production of the potassium and sodium salts was 20,000 tons in 2006.

Cyanamide Chemical compound featuring a nitrile group attached to an amino group

Cyanamide is an organic compound with the formula CN2H2. This white solid is widely used in agriculture and the production of pharmaceuticals and other organic compounds. It is also used as an alcohol-deterrent drug. The molecule features a nitrile group attached to an amino group. Derivatives of this compound are also referred to as cyanamides, the most common being calcium cyanamide (CaCN2).

Ammonium bifluoride Chemical compound

Ammonium hydrogen fluoride is the inorganic compound with the formula NH4HF2 or NH4F·HF. It is produced from ammonia and hydrogen fluoride. This colourless salt is a glass-etchant and an intermediate in a once-contemplated route to hydrofluoric acid.

Ammonium metavanadate Chemical compound

Ammonium metavanadate is the inorganic compound with the formula NH4VO3. It is a white salt, although samples are often yellow owing to impurities of V2O5. It is an important intermediate in the purification of vanadium.

Sodium ferrocyanide Chemical compound

Sodium ferrocyanide is the sodium salt of the coordination compound of formula [Fe(CN)6]4−. In its hydrous form, Na4Fe(CN)6 · 10 H2O (sodium ferrocyanide decahydrate), it is sometimes known as yellow prussiate of soda. It is a yellow crystalline solid that is soluble in water and insoluble in alcohol. The yellow color is the color of ferrocyanide anion. Despite the presence of the cyanide ligands, sodium ferrocyanide has low toxicity (acceptable daily intake 0–0.025 mg/kg body weight). The ferrocyanides are less toxic than many salts of cyanide, because they tend not to release free cyanide. However, like all ferrocyanide salt solutions, addition of an acid can result in the production of hydrogen cyanide gas, which is extremely toxic.

Ammonium cyanide Chemical compound

Ammonium cyanide is an unstable inorganic compound with the formula NH4CN.

Ammonium thiosulfate Chemical compound

Ammonium thiosulfate (ammonium thiosulphate in British English) is an inorganic compound with the formula (NH4)2S2O3. It is white crystalline solid with ammonia odor, readily soluble in water, slightly soluble in acetone and insoluble in ethanol and diethyl ether.

Potassium dicyanoaurate is an inorganic compound with formula K[Au(CN)2]. It is a colorless to white solid that is soluble in water and slightly soluble in alcohol. The salt itself is often not isolated, but solutions of the dicyanoaurate ion ([Au(CN)2]) are generated on a large scale in the extraction of gold from its ores.

References

  1. "GESTIS-Stoffdatenbank". gestis-dguv-de. Retrieved 2022-04-16.
  2. "CALCIUM CYANIDE | CAMEO Chemicals | NOAA".
  3. 1 2 3 Gail, Ernst; Gos, Stephen; Kulzer, Rupprecht; Lorösch, Jürgen; Rubo, Andreas; Sauer, Manfred (2004). "Cyano Compounds, Inorganic". Ullmann's Encyclopedia of Industrial Chemistry . Weinheim: Wiley-VCH. doi:10.1002/14356007.a08_159.pub2.
  4. "Production of Hydrocyanic Acid" United States Patent Office.1933.(accessed April 22, 2012).
  5. Thomas Güthner; Bernd Mertschenk (2006). "Cyanamides". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a08_139.pub2. ISBN   3527306730.
  6. "Use of Cyanide for the Gold Industry" International Cyanide Management Code for the Use of Cyanide in the Gold .2011. http://www.cyanidecode.org/cyanide_use.php (accessed April 22, 2012).