Silver chloride is a
chemical compound
A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one elemen ...
with the
chemical formula Ag Cl. This white
crystalline solid is well known for its low
solubility in
water (this behavior being reminiscent of the chlorides of Tl
+ and Pb
2+). Upon illumination or heating, silver chloride converts to silver (and chlorine), which is signaled by grey to black or purplish coloration to some samples. AgCl occurs naturally as a mineral
chlorargyrite
Chlorargyrite is the mineral form of silver chloride (AgCl). Chlorargyrite occurs as a secondary mineral phase in the oxidation of silver mineral deposits. It crystallizes in the isometric - hexoctahedral crystal class. Typically massive to colum ...
.
Preparation
Silver chloride is unusual in that, unlike most
chloride
The chloride ion is the anion (negatively charged ion) Cl−. It is formed when the element chlorine (a halogen) gains an electron or when a compound such as hydrogen chloride is dissolved in water or other polar solvents. Chloride salts ...
salts, it has very low solubility. It is easily synthesized by
metathesis: combining an
aqueous solution
An aqueous solution is a solution in which the solvent is water. It is mostly shown in chemical equations by appending (aq) to the relevant chemical formula. For example, a solution of table salt, or sodium chloride (NaCl), in water would be ...
of
silver nitrate (which is soluble) with a soluble chloride salt, such as
sodium chloride or
cobalt(II) chloride
Cobalt(II) chloride is an inorganic compound of cobalt and chlorine, with the formula . The compound forms several hydrates ·''n'', for ''n'' = 1, 2, 6, and 9. Claims of the formation of tri- and tetrahydrates have not been confirmed.M. T. Saugi ...
. The silver chloride that forms will precipitate immediately.
:
AgNO3 + NaCl -> AgCl(v) + NaNO3
:
2 AgNO3 + CoCl2 -> 2 AgCl(v) + Co(NO3)2
Structure and reactions
The solid adopts the
''fcc'' NaCl
Sodium chloride , commonly known as salt (although sea salt also contains other chemical salts), is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. With molar masses of 22.99 and 35.45 g/ ...
structure, in which each Ag
+ ion is surrounded by an
octahedron of six chloride ligands.
AgF and
AgBr crystallize similarly. However, the crystallography depends on the condition of crystallization, primarily free silver ion concentration, as is shown on the pictures left (greyish tint and metallic
lustre
Lustre or Luster may refer to:
Places
* Luster, Norway, a municipality in Vestlandet, Norway
** Luster (village), a village in the municipality of Luster
* Lustre, Montana, an unincorporated community in the United States
Entertainment
* ' ...
are due to partly
reduced
silver). AgCl dissolves in solutions containing
ligands such as
chloride
The chloride ion is the anion (negatively charged ion) Cl−. It is formed when the element chlorine (a halogen) gains an electron or when a compound such as hydrogen chloride is dissolved in water or other polar solvents. Chloride salts ...
,
cyanide
Cyanide is a naturally occurring, rapidly acting, toxic chemical that can exist in many different forms.
In chemistry, a cyanide () is a chemical compound that contains a functional group. This group, known as the cyano group, consists of a ...
,
triphenylphosphine,
thiosulfate
Thiosulfate ( IUPAC-recommended spelling; sometimes thiosulphate in British English) is an oxyanion of sulfur with the chemical formula . Thiosulfate also refers to the compounds containing this anion, which are the salts of thiosulfuric acid, e ...
,
thiocyanate and
ammonia
Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous wa ...
. Silver chloride reacts with these ligands according to the following illustrative equations:
:
AgCl (s) + Cl^- (aq) -> AgCl2^- (aq)
:
AgCl (s) + 2 S2O3^2- (aq) ->(Ag(S2O3)2)^3- (aq) + Cl^- (aq)
:
AgCl (s) + 2 NH3(aq) -> Ag(NH3)2+ (aq) + Cl^- (aq)
Silver chloride does not react with nitric acid.
Most complexes derived from AgCl are two-, three-, and, in rare cases, four-coordinate, adopting linear, trigonal planar, and tetrahedral coordination geometries, respectively.
:
3AgCl(s) + Na3AsO3(aq) -> Ag3AsO3(s) + 3NaCl(aq)
:
3AgCl(s) +Na3AsO4(aq) -> Ag3AsO4(s) + 3NaCl(aq)
Above 2 reactions are particularly important in
qualitative analysis of AgCl in labs as AgCl is white in colour, which changes to
Ag3AsO3 (silver arsenite) which is yellow in colour or
Ag3AsO4(
Silver arsenate) which is reddish brown in colour.
Chemistry
In one of the most famous reactions in chemistry, addition of colorless aqueous
silver nitrate to an equally colorless solution of sodium chloride produces an opaque white precipitate of AgCl:
:
Ag+ (aq) + Cl^- (aq) -> AgCl (s)
This conversion is a common test for the presence of
chloride
The chloride ion is the anion (negatively charged ion) Cl−. It is formed when the element chlorine (a halogen) gains an electron or when a compound such as hydrogen chloride is dissolved in water or other polar solvents. Chloride salts ...
in solution. Due to its conspicuousness it is easily used in titration, which gives the typical case of
argentometry In analytical chemistry, argentometry is a type of titration involving the silver(I) ion. Typically, it is used to determine the amount of chloride present in a sample. The sample solution is titrated against a solution of silver nitrate of known ...
.
The
solubility product Solubility equilibrium is a type of dynamic equilibrium that exists when a chemical compound in the solid state is in chemical equilibrium with a solution of that compound. The solid may dissolve unchanged, with dissociation, or with chemical reac ...
, ''K''
sp, for AgCl in water is at room temperature, which indicates that only 1.9 mg (that is,
) of AgCl will dissolve per liter of water. The chloride content of an aqueous solution can be determined quantitatively by weighing the precipitated AgCl, which conveniently is non-hygroscopic, since AgCl is one of the few transition metal chlorides that is unreactive toward water. Interfering ions for this test are bromide and iodide, as well as a variety of ligands (see
silver halide). For AgBr and AgI, the ''K''
sp values are 5.2 x 10
−13 and 8.3 x 10
−17, respectively.
Silver bromide (slightly yellowish white) and
silver iodide (bright yellow) are also significantly more photosensitive than is AgCl.
AgCl quickly darkens on exposure to light by disintegrating into elemental
chlorine
Chlorine is a chemical element with the symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine is ...
and metallic
silver. This reaction is used in photography and film.
Uses
*The
silver chloride electrode
A silver chloride electrode is a type of reference electrode, commonly used in electrochemical measurements. For environmental reasons it has widely replaced the saturated calomel electrode. For example, it is usually the internal reference elect ...
is a common reference electrode in
electrochemistry
Electrochemistry is the branch of physical chemistry concerned with the relationship between electrical potential difference, as a measurable and quantitative phenomenon, and identifiable chemical change, with the potential difference as an outco ...
.
*Silver chloride's low solubility makes it a useful addition to pottery glazes for the production of "Inglaze
lustre
Lustre or Luster may refer to:
Places
* Luster, Norway, a municipality in Vestlandet, Norway
** Luster (village), a village in the municipality of Luster
* Lustre, Montana, an unincorporated community in the United States
Entertainment
* ' ...
".
*Silver chloride has been used as an antidote for
mercury poisoning, assisting in the elimination of
mercury.
*Silver chloride is used:
** to make
photographic paper since it reacts with photons to form
latent image and via photoreduction
** in
photochromic lenses, again taking advantage of its reversible conversion to Ag metal
** in
bandage
A bandage is a piece of material used either to support a medical device such as a dressing or splint, or on its own to provide support to or to restrict the movement of a part of the body. When used with a dressing, the dressing is applie ...
s and wound healing products
** to create yellow, amber, and brown shades in
stained glass
Stained glass is coloured glass as a material or works created from it. Throughout its thousand-year history, the term has been applied almost exclusively to the windows of churches and other significant religious buildings. Although tradition ...
manufacture
** as an
infrared transmissive optical component as it can be hot-pressed into window and lens shapes
** as an antimicrobial agent:
*** in some personal deodorant products
*** for long-term preservation of drinking water in water tanks
See also
*
Photosensitive glass
References
{{DEFAULTSORT:Silver Chloride
Chlorides
Silver compounds
Metal halides
Coordination complexes
Photographic chemicals
Light-sensitive chemicals
Rock salt crystal structure