Silver chloride Formula
Silver chloride, also known as chlorargyrite, is inorganic salt very use as a component of photographic papers and film and in some analytic methods to valid the quantity of chloride ions in solution.
Formula and structure: Silver chloride chemical formula is AgCl and its molar mass is 143.318 g mol-1. Silver chloride is formed by the cation Ag+) and the anion Cl-. Silver chloride has a face centered cubic crystal structure with an unit cells forms by one cation surrounded by 6 anions (it can also be considered one anion surrounded by 6 cations) and it is very similar to other silver halide and even sodium chloride NaCl. It has also been reported other type of crystal structure depending of the crystallization conditions. Its chemical structure can be written as below, in the common representations used for organic molecules.
Occurrence: Silver chloride is found in nature in some minerals such as chlorargyrite.
Preparation: Silver chloride is also obtained by chemical synthesis. The main method for obtaining is similar to silver bromide and other silver halide. It is prepared using a reaction between silver nitrate and sodium chloride in aqueous medium:AgNO3 + NaCl → AgCl(s)+ Na+ + NO3- AgNO3 + NaCl → AgCl(s)+ Na+ + NO3-
Physical properties: Silver chloride is a white crystalline solid. Its density is 5.56 g mL-1. Its melting point is 455 ºC and its boiling point is 1550 ºC. It is insoluble in water, dilute acids and alcohols, but it is very soluble in ammonia, hydrochloric and sulfuric acids, potassium bromide solution and alkali cyanide.
Chemical properties: The reactivity profile of silver chloride is also similar to the silver bromide, which include many silver complex that can be formed when the AgCl react with ligands such as chloride and ammonia:
AgCl(s) + Cl- → AgCl2-
AgCl(s) + 2NH3 → [Ag(NH3)2]+ + Cl-
Moreover, silver chloride is well known by the reaction which allow the detection of chloride in a determinate solution. In this reaction, silver nitrate is added to the sample and the formation of a white precipitated of silver chloride will indicate the presence of chloride ions:
AgNO3 + Cl- → AgCl(s)
Uses: Silver chloride is used to measure the quantity of chloride in a determinate solution, in a method known as argentometry. Moreover it is also added to photography supplies and film due AgCl decomposes when exposed to the light. Other uses include the production of electrodes, photochromic lenses and other optical components. In medicine, it is use as an antidote for mercury poisoning.
Health effects / safety hazards: Silver chloride is very toxic to environment, especially to the wild life in lakes and rivers. It can cause irritation in eyes, respiratory system and skin. It is corrosive to metals. Silver chloride is decomposed by light.