Silver cyanide

Last updated
Silver cyanide
40 grams of silver cyanide on scale.png
40 grams of silver cyanide on a scale.
Names
IUPAC name
Silver cyanide
Other names
Argentous cyanide
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.007.317 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 208-048-6
PubChem CID
RTECS number
  • VW3850000
UNII
UN number 1684
  • InChI=1S/CN.Ag/c1-2;/q-1;+1 Yes check.svgY
    Key: LFAGQMCIGQNPJG-UHFFFAOYSA-N Yes check.svgY
  • InChI=1/CN.Ag/c1-2;/q-1;+1
    Key: LFAGQMCIGQNPJG-UHFFFAOYAM
  • [C-]#N.[Ag+]
Properties
AgCN
Molar mass 133.8856 g/mol
Appearancecolorless, gray (impure) crystals
Odor odorless
Density 3.943 g/cm3
Melting point 335 °C (635 °F; 608 K) (decomposes)
0.000023 g/100 mL (20 °C)
5.97×1017 [1]
Solubility soluble in concentrated ammonia, boiling nitric acid, ammonium hydroxide, KCN
insoluble in alcohol, dilute acid
43.2·10−6 cm3/mol
1.685
Structure
hexagonal
linear
Thermochemistry
Std molar
entropy
(S298)
84 J·mol−1·K−1 [2]
146 kJ·mol−1 [2]
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
toxic
GHS labelling:
GHS-pictogram-acid.svg GHS-pictogram-skull.svg GHS-pictogram-pollu.svg
Danger
H290, H300, H310, H315, H318, H330, H410
P234, P260, P262, P264, P270, P271, P273, P280, P284, P301+P310, P302+P350, P302+P352, P304+P340, P305+P351+P338, P310, P320, P321, P322, P330, P332+P313, P361, P362, P363, P390, P391, P403+P233, P404, P405, P501
NFPA 704 (fire diamond)
NFPA 704.svgHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilInstability 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g. calciumSpecial hazards (white): no code
3
1
1
Flash point 320 °C (608 °F; 593 K)
Lethal dose or concentration (LD, LC):
123 mg/kg (oral, rat)
Related compounds
Other anions
AgCl
Other cations
NaCN
Copper(I) 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 ?)
Structure of silver cyanide. Silver-cyanide-xtal-1x1x3-3D-bs-17.png
Structure of silver cyanide.

Silver cyanide is the chemical compound with the formula AgCN. It is a white salt that is precipitated upon treatment of solutions containing Ag+ with cyanide, which is used in some schemes to recover silver from solution. Silver cyanide is used in silver-plating.

Contents

Structure

The structure of silver cyanide consists of -[Ag-CN]- chains in which the linear two-coordinate Ag+ ions are bridged by the cyanide ions, [3] typical of silver(I) and other d10 ions. This is the same binding mode as seen in the more famous case of Prussian blue. These chains then pack hexagonally with adjacent chains offset by +/- 1/3 of the c lattice parameter. This is the same as the structure adopted by the high temperature polymorph of copper(I) cyanide. The silver to carbon and silver to nitrogen bond lengths in AgCN are both ~2.06 Å [4] and the cyanide groups show head-to-tail disorder. [5]

Reactions

AgCN precipitates upon the addition of sodium cyanide to a solution containing Ag+. On the addition of further cyanide, the precipitate dissolves to form linear [Ag(CN)2](aq) and [Ag(CN)3]2−(aq). Silver cyanide is also soluble in solutions containing other ligands such as ammonia or tertiary phosphines.

Silver cyanides form structurally complex materials upon reaction with other anions. [6] Some silver cyanides are luminescent. [7]

Uses

"Cyanidation" is widely used in the isolation of silver from its ores. Partial purification of silver compounds is usually effected by froth flotation. The silver ion is then separated from the skimmed froth with cyanide, yielding a solution of [Ag(CN)2]. The silver metal can then be plated out by electrolysis of such solutions. [8]

Both AgCN and KAg(CN)2 have been used in silver-plating solutions since at least 1840 when the Elkington brothers patented their recipe for a silver-plating solution. A typical, traditional silver-plating solution would contain 15-40 g·L−1 KAg(CN)2 , 12-120 g·L−1 KCN and 15 g·L−1 K2CO3. [9]

See also

Related Research Articles

<span class="mw-page-title-main">Cyanide</span> Any molecule with a cyano group (–C≡N)

In chemistry, 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.

<span class="mw-page-title-main">Coordination complex</span> Molecule or ion containing ligands datively bonded to a central metallic atom

A coordination complex is a chemical compound consisting of a central atom or ion, which is usually metallic and is called the coordination centre, and a surrounding array of bound molecules or ions, that are in turn known as ligands or complexing agents. Many metal-containing compounds, especially those that include transition metals, are coordination complexes.

<span class="mw-page-title-main">Potassium ferrocyanide</span> Chemical compound

Potassium hexacyanidoferrate(II) 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.

<span class="mw-page-title-main">Silver chloride</span> Chemical compound with the formula AgCl

Silver chloride is an inorganic chemical compound with the chemical formula AgCl. This white crystalline solid is well known for its low solubility in water and its sensitivity to light. Upon illumination or heating, silver chloride converts to silver, which is signaled by grey to black or purplish coloration in some samples. AgCl occurs naturally as the mineral chlorargyrite.

<span class="mw-page-title-main">Cyanate</span> Anion with formula OCN and charge –1

The cyanate ion is an anion with the chemical formula OCN. It is a resonance of three forms: [O−C≡N] (61%) ↔ [O=C=N] (30%) ↔ [O+≡C−N2−] (4%).

<span class="mw-page-title-main">Tin(II) chloride</span> Chemical compound

Tin(II) chloride, also known as stannous chloride, is a white crystalline solid with the formula SnCl2. It forms a stable dihydrate, but aqueous solutions tend to undergo hydrolysis, particularly if hot. SnCl2 is widely used as a reducing agent (in acid solution), and in electrolytic baths for tin-plating. Tin(II) chloride should not be confused with the other chloride of tin; tin(IV) chloride or stannic chloride (SnCl4).

<span class="mw-page-title-main">Copper(I) cyanide</span> Chemical compound

Copper(I) cyanide is an inorganic compound with the formula CuCN. This off-white solid occurs in two polymorphs; impure samples can be green due to the presence of Cu(II) impurities. The compound is useful as a catalyst, in electroplating copper, and as a reagent in the preparation of nitriles.

<span class="mw-page-title-main">Silver carbonate</span> Chemical compound

Silver carbonate is the chemical compound with the formula Ag2CO3. This salt is yellow but typical samples are grayish due to the presence of elemental silver. It is poorly soluble in water, like most transition metal carbonates.

<span class="mw-page-title-main">Silver azide</span> Chemical compound

Silver azide is the chemical compound with the formula AgN3. It is a silver(I) salt of hydrazoic acid. It forms a colorless crystals. Like most azides, it is a primary explosive.

Iron shows the characteristic chemical properties of the transition metals, namely the ability to form variable oxidation states differing by steps of one and a very large coordination and organometallic chemistry: indeed, it was the discovery of an iron compound, ferrocene, that revolutionalized the latter field in the 1950s. Iron is sometimes considered as a prototype for the entire block of transition metals, due to its abundance and the immense role it has played in the technological progress of humanity. Its 26 electrons are arranged in the configuration [Ar]3d64s2, of which the 3d and 4s electrons are relatively close in energy, and thus it can lose a variable number of electrons and there is no clear point where further ionization becomes unprofitable.

Potassium dicyanoargentate is an inorganic compound with the formula KAg(CN)2. A white solid, it is the K+ salt of the linear coordination complex [Ag(CN)2]. It forms upon treatment of virtually any silver salt with two equivalents of potassium cyanide.

The perrhenate ion is the anion with the formula ReO
4
, or a compound containing this ion. The perrhenate anion is tetrahedral, being similar in size and shape to perchlorate and the valence isoelectronic permanganate. The perrhenate anion is stable over a broad pH range and can be precipitated from solutions with the use of organic cations. At normal pH, perrhenate exists as metaperrhenate, but at high pH mesoperrhenate forms. Perrhenate, like its conjugate acid perrhenic acid, features rhenium in the oxidation state of +7 with a d0 configuration. Solid perrhenate salts takes on the color of the cation.

Cyanometallates or cyanometalates are a class of coordination compounds, most often consisting only of cyanide ligands. Most are anions. Cyanide is a highly basic and small ligand, hence it readily saturates the coordination sphere of metal ions. The resulting cyanometallate anions are often used as building blocks for more complex structures called coordination polymers, the best known example of which is Prussian blue, a common dyestuff.

<span class="mw-page-title-main">Cyanonickelate</span> Class of chemical compounds

The cyanonickelates are a class of chemical compound containing anions consisting of nickel atoms, and cyanide groups. The most important of these are the tetracyanonickelates containing four cyanide groups per nickel. The tetracyanonickelates contain the [Ni(CN)4]2− anion. This can exist in solution or in solid salts. The ion has cyanide groups arranged in a square around the central nickel ion. The symmetry of the ion is D4h. The distance from the nickel atom to the carbon is 1.87 Å, and the carbon-nitrogen distance is 1.16 Å. In their crystals, the tetracyanonickelate(II) anions are often arranged in a columnar structure (e.g. in K2[Ni(CN)4]). Tetracyanonickelate(II) can be oxidised electrochemically in solution to yield tetracyanonickelate(III) [Ni(CN)4]. [Ni(CN)4] is unstable and Ni(III) oxidises the cyanide to cyanate OCN. Tetracyanonickelate(III) can add two more cyanide groups to form hexacyanonickelate(III).

The fluorosulfates or fluorosulfonates are a set of salts of fluorosulfuric acid with an ion formula SO3F. The fluorosulfate anion can be treated as though it were a hydrogen sulfate anion with hydroxyl substituted by fluorine. The fluorosulfate ion has a low propensity to form complexes with metal cations. Since fluorine is similar in size to oxygen, the fluorosulfate ion is roughly tetrahedral and forms salts similar to those of the perchlorate ion. It is isoelectronic with sulfate, SO4−2. When an organic group is substituted for the anions, organic fluorosulfonates are formed.

<span class="mw-page-title-main">Phosphenium</span> Divalent cations of phosphorus

Phosphenium ions, not to be confused with phosphonium or phosphirenium, are divalent cations of phosphorus of the form [PR2]+. Phosphenium ions have long been proposed as reaction intermediates.

Sulfidostannates, or thiostannates are chemical compounds containing anions composed of tin linked with sulfur. They can be considered as stannates with sulfur substituting for oxygen. Related compounds include the thiosilicates, and thiogermanates, and by varying the chalcogen: selenostannates, and tellurostannates. Oxothiostannates have oxygen in addition to sulfur. Thiostannates can be classed as chalcogenidometalates, thiometallates, chalcogenidotetrelates, thiotetrelates, and chalcogenidostannates. Tin is almost always in the +4 oxidation state in thiostannates, although a couple of mixed sulfides in the +2 state are known,

Sulfidogermanates or thiogermanates are chemical compounds containing anions with sulfur atoms bound to germanium. They are in the class of chalcogenidotetrelates. Related compounds include thiosilicates, thiostannates, selenidogermanates, telluridogermanates and selenidostannates.

<span class="mw-page-title-main">Gold(I) cyanide</span> Chemical compound

Gold(I) cyanide is the inorganic compound with the chemical formula AuCN. It is the binary cyanide of gold(I). It is an odourless, tasteless yellow solid. Wet gold(I) cyanide is unstable to light and will become greenish. Gold(I) cyanide itself is only of academic interest, but its derivative dicyanoaurate is an intermediate in gold cyanidation, the extraction of gold from its ores.

<span class="mw-page-title-main">Selenocyanate</span> Class of chemical compounds

A selenocyanate is an ion or chemical compound that contains the -SeCN group, which could be in the form of an anion, SeCN. Organic selenocyanates also exist.

References

  1. John Rumble (June 18, 2018). CRC Handbook of Chemistry and Physics (99 ed.). CRC Press. pp. 5–189. ISBN   978-1138561632.
  2. 1 2 Zumdahl, Steven S. (2009). Chemical Principles 6th Ed. Houghton Mifflin Company. p. A23. ISBN   978-0-618-94690-7.
  3. Bowmaker, Graham A.; Kennedy, Brendan J.; Reid, Jason C. (1998). "Crystal Structures of AuCN and AgCN and Vibrational Spectroscopic Studies of AuCN, AgCN, and CuCN". Inorg. Chem. 37 (16): 3968–3974. doi:10.1021/ic9714697. PMID   11670511.
  4. Hibble, S. J.; Cheyne, S. M.; Hannon, A. C.; Eversfield, S. G. (2002). "Beyond Bragg scattering: the structure of AgCN determined from total neutron diffraction". Inorganic Chemistry. 41 (5): 1042–1044. doi:10.1021/ic015610u. PMID   11874335.
  5. Bryce, David L.; Wasylishen, Roderick E. (2002). "Insight into the Structure of Silver Cyanide from 13C and 15N Solid-State NMR Spectroscopy". Inorganic Chemistry. 41 (16): 4131–4138. doi:10.1021/ic0201553. ISSN   0020-1669. PMID   12160400.
  6. Urban, Victoria; Pretsch, Thorsten; Hartl, Hans (2005-04-29). "From AgCN Chains to a Fivefold Helix and a Fishnet-Shaped Framework Structure". Angewandte Chemie International Edition. 44 (18): 2794–2797. doi:10.1002/anie.200462793. ISSN   1433-7851. PMID   15830404.
  7. Omary, Mohammad A.; Webb, Thomas R.; Assefa, Zerihun; Shankle, George E.; Patterson, Howard H. (1998). "Crystal Structure, Electronic Structure, and Temperature-Dependent Raman Spectra of Tl[Ag(CN)2]: Evidence for Ligand-Unsupported Argentophilic Interactions". Inorganic Chemistry. 37 (6): 1380–1386. doi:10.1021/ic970694l. ISSN   0020-1669. PMID   11670349.
  8. Etris, S. F. (2010). "Silver and Silver Alloys". Kirk-Othmer Encyclopedia of Chemical Technology. pp. 1–43. doi:10.1002/0471238961.1909122205201809.a01.pub3. ISBN   978-0471238966.
  9. Blair, Alan (2000). "Silver plating". Metal Finishing. 98 (1): 298–303. doi:10.1016/S0026-0576(00)80339-6.