Silver chloride

Names
IUPAC name Silver(I) chloride
Other names Cerargyrite Chlorargyrite Horn silver Argentous chloride
Identifiers
CAS Number	7783-90-6 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:30341 Y
ChemSpider	22967 Y
ECHA InfoCard	100.029.121
PubChem CID	24561
RTECS number	VW3563000
UNII	MWB0804EO7 Y
CompTox Dashboard (EPA)	DTXSID4035251
InChI InChI=1S/Ag.ClH/h;1H/q+1;/p-1 Y Key: HKZLPVFGJNLROG-UHFFFAOYSA-M Y InChI=1S/Ag.ClH/h;1H/q+1;/p-1 Key: HKZLPVFGJNLROG-UHFFFAOYSA-M
SMILES Cl
Properties
Chemical formula	AgCl
Molar mass	143.32 g·mol−1
Appearance	White solid
Density	5.56 g cm−3
Melting point	455 °C (851 °F; 728 K)
Boiling point	1,547 °C (2,817 °F; 1,820 K)
Solubility in water	520 μg/100 g at 50 °C
Solubility product (Ksp)	1.77×10−10[1]
Solubility	soluble in NH3, conc. HCl, conc. H2SO4, alkali cyanide, (NH4)2CO3, KBr, Na2S2O3; insoluble in alcohol, dilute acids.
Magnetic susceptibility (χ)	−49.0·10−6 cm3/mol
Refractive index (nD)	2.071
Structure[2]
Crystal structure	cubic
Space group	Fm3m (No. 225)
Lattice constant	a = 555 pm
Coordination geometry	Octahedral
Thermochemistry
Std molar entropy (S⦵298)	96 J·mol−1·K−1[3]
Std enthalpy of formation (ΔfH⦵298)	−127 kJ·mol−1[3]
Hazards
NFPA 704 (fire diamond)	2 0 0
Safety data sheet (SDS)	Fischer Scientific, Salt Lake Metals
Related compounds
Other anions	silver(I) fluoride, silver bromide, silver iodide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). N verify (what is YN ?) Infobox references

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 (and chlorine), which is signaled by grey to black or purplish coloration in some samples. AgCl occurs naturally as the mineral chlorargyrite.

It is produced by a metathesis reaction for use in photography and in pH meters as electrodes.

Preparation

Silver chloride is unusual in that, unlike most chloride salts, it has very low solubility. It is easily synthesized by metathesis: combining an aqueous solution of silver nitrate (which is soluble) with a soluble chloride salt, such as sodium chloride (which is used industrially as a method of producing AgCl), or cobalt(II) chloride. The silver chloride that forms will precipitate immediately.^[3][4]: 46

${\displaystyle {\ce {AgNO3 + NaCl -> AgCl(v) + NaNO3}}}$

${\displaystyle {\ce {2 AgNO3 + CoCl2 -> 2 AgCl(v) + Co(NO3)2}}}$

It can also be produced by the reaction of silver metal and aqua regia; however, the insolubility of silver chloride decelerates the reaction. Silver chloride is also a by-product of the Miller process, where silver metal is reacted with chlorine gas at elevated temperatures.^{[4]: 21 [5]}

History

Silver chloride has been known since ancient times. Ancient Egyptians produced it as a method of refining silver, which was done by roasting silver ores with salt to produce silver chloride, which was subsequently decomposed to silver and chlorine.^[4]: 19 However, it was later identified as a distinct compound of silver in 1565 by Georg Fabricius.^[6][7] Silver chloride, historically known as luna cornea (which could be translated as "horn silver" as the moon was an alchemic codename for silver),^[7] has also been an intermediate in other historical silver refining processes. One such example is the Augustin process developed in 1843, wherein copper ore containing small amounts of silver is roasted in chloridizing conditions and the silver chloride produced is leached by brine, where it is more soluble.^[4]: 32

Silver-based photographic films were first made in 1727 by Johann Heinrich Schulze with silver nitrate. However, he was not successful in making permanent images, as they faded away.^[8] Later in 1816, the use of silver chloride was introduced into photography by Nicéphore Niépce.^{[4]: 38–39 [9]}

Structure

The solid adopts the fcc NaCl structure, in which each Ag⁺ ion is surrounded by an octahedron of six chloride ligands. AgF and AgBr crystallize similarly.^[10] However, the crystallography depends on the condition of crystallization, primarily free silver ion concentration, as is shown in the picture to the left (greyish tint and metallic lustre are due to partially reduced silver).^[11]

Above 7.5 GPa, silver chloride transitions into a monoclinic KOH phase. Then at 11 GPa, it undergoes another phase change to an orthorhombic TlI phase.^[2]

Reactions

AgCl dissolves in solutions containing ligands such as chloride, cyanide, triphenylphosphine, thiosulfate, thiocyanate and ammonia. Silver chloride reacts with these ligands according to the following illustrative equations:^{[4]: 25–33}

${\displaystyle {\ce {AgCl (s) + 2 CN^- (aq) -> Ag(CN)2^- (aq) + Cl^- (aq)}}}$

${\displaystyle {\ce {AgCl (s) + 2 S2O3^2- (aq) ->(Ag(S2O3)2)^3- (aq) + Cl^- (aq)}}}$

${\displaystyle {\ce {AgCl (s) + 2 NH3(aq) -> Ag(NH3)2+ (aq) + Cl^- (aq)}}}$

Of these reactions used to leach silver chloride from silver ores, cyanidation is the most commonly used. Cyanidation produces the soluble dicyanoargentate complex, which is later turned back to silver by reduction.^[4]: 26

Silver chloride does not react with nitric acid, but instead reacts with sulfuric acid to produce silver sulfate.^[12] Then the sulfate is protonated in the presence of sulfuric acid to bisulfate, which can be reversed by dilution. This reaction is used to separate silver from other platinum group metals.^[4]: 42

Most complexes derived from AgCl are two-, three-, and, in rare cases, four-coordinate, adopting linear, trigonal planar, and tetrahedral coordination geometries, respectively.^[13]

${\displaystyle 3\text{AgCl}(\text{s})+{\text{Na}}_3^{}{\text{AsO}}_3^{}(\text{aq})⟶<!--\; ⟶\; -->{\text{Ag}}_3^{}}$Zdroj:https://en.wikipedia.org?pojem=Silver_chloride
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