Silver phosphate or silver orthophosphate is a light sensitive, yellow, water-insoluble chemical compound composed of

silver Silver is a chemical element; it has Symbol (chemistry), symbol Ag () and atomic number 47. A soft, whitish-gray, lustrous transition metal, it exhibits the highest electrical conductivity, thermal conductivity, and reflectivity of any metal. ...

and

phosphate Phosphates are the naturally occurring form of the element phosphorus. In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthop ...

ions of formula Ag₃ P O₄.

Synthesis, reactions and properties

Silver phosphate is formed as a yellow solid precipitate by the reaction between a soluble silver salt, such as

silver nitrate Silver nitrate is an inorganic compound with chemical formula . It is a versatile precursor to many other silver compounds, such as those used in photography. It is far less sensitive to light than the halides. It was once called ''lunar causti ...

, with a soluble

orthophosphate In chemistry, a phosphoric acid, in the general sense, is a phosphorus oxoacid in which each phosphorus (P) atom is in the oxidation state +5, and is bonded to four oxygen (O) atoms, one of them through a double bond, arranged as the corners ...

. Its

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 ...

is 8.89×10⁻¹⁷ mol⁴·dm⁻². The precipitation reaction is analytically significant and can be used in qualitative or quantitative analysis. This compound dissolves in aqueous

ammonia Ammonia is an inorganic chemical compound of nitrogen and hydrogen with the chemical formula, formula . A Binary compounds of hydrogen, stable binary hydride and the simplest pnictogen hydride, ammonia is a colourless gas with a distinctive pu ...

. Large crystals of silver phosphate form upon gradual evaporation of such ammoniacal solutions. Its structure has been confirmed by

X-ray crystallography X-ray crystallography is the experimental science of determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to Diffraction, diffract in specific directions. By measuring th ...

Uses

The precipitation of silver phosphate is useful in traditional

analytical chemistry Analytical skill, Analytical chemistry studies and uses instruments and methods to Separation process, separate, identify, and Quantification (science), quantify matter. In practice, separation, identification or quantification may constitute t ...

. Precipitation of silver phosphate is also used in silver staining of biological materials (after reduction to silver metal) - as a magnifying agent for phosphate. Silver phosphate also found use in early photography as a light sensitive agent. Silver phosphate exhibits antibacterial properties.

Research

Silver phosphate is a high (90%)

quantum yield In particle physics, the quantum yield (denoted ) of a radiation-induced process is the number of times a specific event occurs per photon absorbed by the system. \Phi(\lambda)=\frac Applications Fluorescence spectroscopy The fluorescence ...

photocatalyst In chemistry, photocatalysis is the acceleration of a photoreaction in the presence of a photocatalyst, the excited state of which "repeatedly interacts with the reaction partners forming reaction intermediates and regenerates itself after each ...

for the visible light photochemical splitting of water and for production of activated oxygen by the same method.

Other silver phosphates

Silver pyrophosphate Ag₄P₂O₇ (CAS No. 13465-97-9) can be prepared as a white precipitate from reaction of silver(I) and

pyrophosphate In chemistry, pyrophosphates are phosphorus oxyanions that contain two phosphorus atoms in a linkage. A number of pyrophosphate salts exist, such as disodium pyrophosphate () and tetrasodium pyrophosphate (), among others. Often pyrophosphates a ...

ions. Like silver orthophosphate it is light sensitive. Silver orthophosphate turns red on exposure to light. It has a density of 5.306 g/cm³ and a melting point of 585 °C.Bulletin of the National Research Council, National Research Council (U.S.A), 1950, pp.56-5
google books link
/ref> A hydrate also exists which decomposes at 110 °C. Silver metaphosphate (AgPO₃) (CAS No. 13465-96-8)
''www.chemicalbook.com'' is a white solid with a density of 6.370 g/cm³ and a melting point of 482 °C. A hydrate also exists which decomposes at 240 °C.

References

{{Phosphates Silver compounds Phosphates