Zilverchloride

Zilverchloride, known in English as silver chloride and chemical formula AgCl, is an inorganic salt that forms when silver ions meet chloride ions. It appears as a white, crystalline solid and is nearly insoluble in water. In aqueous solution it dissociates into Ag+ and Cl−, and its solubility is governed by a solubility product of about 1.8 × 10−10 at 25°C.

Silver chloride is notable for its photoreactivity. Upon exposure to light, it undergoes a photochemical reduction to metallic silver, described by the equation 2 AgCl → 2 Ag + Cl2. This light sensitivity underlies historical photography, where silver chloride-containing emulsions darkened to form images.

Preparation and notable reactions. AgCl forms as a white precipitate when solutions containing Ag+ are treated with chloride ions, for example by mixing silver nitrate with a chloride source. In solution it can be dissolved by ammonia, forming the diamminesilver complex [Ag(NH3)2]+, and it can also form soluble thiosilver complexes in the presence of thiosulfate. Because of its low solubility, AgCl is commonly used as a qualitative indicator for chloride ions in analytical chemistry.

Uses. Historically important in photography as a light-sensitive component of photographic emulsions and papers. In electrochemistry, the silver/silver chloride electrode uses a coating of AgCl on silver to establish a stable reference potential. AgCl preparations are also used in qualitative chloride tests and, in a broader sense, as a reagent in various analytical procedures.

Occurrence and safety. The mineral chlorargyrite is the natural form of AgCl and occurs in oxidized silver ore deposits. Silver chloride is of low solubility, which limits systemic exposure, but it can be irritant if inhaled as dust and should be handled with appropriate precautions.