- Silver nitrate (AgNO₃) is an inorganic compound composed of silver, nitrogen, and oxygen. It is one of the most important and versatile silver salts used in laboratories, industry, and medicine. In its pure form, silver nitrate appears as colorless, transparent crystals that are highly soluble in water, forming a colorless solution. It is the primary source of various other silver compounds, as it readily reacts with halides, sulfides, and other anions to form corresponding silver salts such as silver chloride, silver bromide, and silver sulfide.
- Silver nitrate crystallizes in the orthorhombic crystal system and has a molecular weight of 169.87 g/mol. It melts at approximately 212°C, decomposing at higher temperatures to yield silver, nitrogen dioxide, and oxygen gases. The compound is odorless but has a bitter metallic taste, and it is non-volatile under normal conditions. It is light-sensitive, gradually darkening upon exposure to light due to the photochemical reduction of silver ions to metallic silver. Silver nitrate is highly soluble in water, ethanol, and acetone, forming an aqueous solution that serves as a powerful oxidizing agent.
- Silver nitrate is typically prepared by dissolving metallic silver or silver oxide in dilute nitric acid, followed by evaporation of the solution to crystallize the compound:
- 3Ag + 4HNO₃ → 3AgNO₃ + 2H₂O + NO
- As a reactive compound, silver nitrate participates in numerous chemical reactions. When treated with halide ions (Cl⁻, Br⁻, I⁻), it forms insoluble precipitates of silver halides—AgCl, AgBr, and AgI—a principle widely used in qualitative inorganic analysis to identify halide ions. It also reacts with organic compounds containing hydroxyl or amino groups, and serves as a precursor for producing silver oxide, silver carbonate, and metallic silver through controlled reduction processes.
- Silver nitrate has broad applications across multiple disciplines. In analytical chemistry, it is employed in titrations, particularly in Mohr’s method for chloride ion determination. In medicine, it has been historically used as an antiseptic and cauterizing agent due to its strong antimicrobial properties. Dilute solutions (1–2%) of silver nitrate were once applied to prevent ophthalmia neonatorum (eye infection in newborns) caused by Neisseria gonorrhoeae. In industry, silver nitrate serves as the key starting material for manufacturing photographic films, mirrors, silver plating, and explosive silver compounds such as silver fulminate and silver azide. It is also used in the synthesis of nanoparticles for advanced materials and biomedical applications.
- Although silver nitrate is not highly toxic in small quantities, it is a strong oxidizing agent and should be handled with care. Contact with skin results in black or brown stains, caused by the reduction of silver ions to metallic silver upon exposure to light. Prolonged or repeated exposure can cause skin irritation or argyria, a condition characterized by bluish-gray discoloration of the skin due to silver deposition. Ingestion or inhalation of large amounts can be harmful, and protective gloves and eyewear are recommended when handling the compound. Silver nitrate solutions should be stored in dark, tightly sealed containers to prevent photodecomposition.
- From an environmental perspective, silver nitrate and its derivatives have notable antimicrobial and catalytic properties that are exploited in water purification and pollution control. Its ability to release Ag⁺ ions, which are toxic to bacteria and fungi, makes it useful in sterilization and environmental disinfection. Chemically, silver nitrate is regarded as the gateway compound to nearly all other silver salts, owing to its solubility, reactivity, and straightforward synthesis.
