Silver Chloride

Author: Hans Lohninger

AgCl adopts the fcc NaCl structure, in which Ag⁺ ions are surrounded by octahedrons of six chloride ligands.

Chemistry

AgCl dissolves in solutions containing chloride, cyanide, thiosulfate, or ammonium ions by forming complexes according to the following equations:

AgCl(s) + Cl^-(aq) AgCl₂^-(aq)
AgCl(s) + 2CN^-(aq) Ag(CN)₂^-(aq) + Cl^-(aq)
AgCl(s) + 2 S₂O₃^2-(aq) Ag[(S₂O₃)₂]^3-(aq) + Cl^-(aq)
AgCl(s) + 2 NH₄OH(aq) Ag[(NH₃)₂]⁺(aq) + Cl^-(aq) + 2 H₂O

Due to the low solubility product of silver chloride, AgCl precipitates when a colorless silver nitrate solution ist mixed with a colorless sodium chloride solution:

Ag⁺(aq) + Cl^-(aq) AgCl(s)

The opaque white precipitate of AgCl quickly darkens on exposure to light. This reaction is a common test for the presence of chloride in a solution. The solubility product, K_sp, for AgCl is 1.810^-10; the solubility of AgCl in water is 1.9 mg/l at room temperature.

Usage

• Photographic paper: silver chloride is reduced by photons to form a latent image (however, normally silver bromide is used for photographic papers)
• Photochromic lenses: silver chloride is used in photochromic lenses (lenses which change their color when hit by sunlight)
• Silver chloride is used as the cathode in seawater-activated batteries (Mg/AgCl cells)
• The silver electrode is a common reference electrode in electrochemistry.
• Stained glass manufacture: silver chloride creates yellow, amber, and brown shades