Silver iodide is a yellowish-white powder used in photography, as a pigment, and in manufacturing certain types of glass. It is also an antiseptic and has several other medical uses. Ingestion of large amounts can lead to argyria, a condition characterized by darkening of the skin, eyes and throat. Silver iodide is a common ingredient in oral and eye drops.
In a photochemical process, silver iodide is used to produce a photographic image by the interaction of light with silver halides contained in a binder applied to a substrate. It is also used as an antiseptic for mucous membranes, in electronic and optical applications and in cloud seeding.
In the field of artificially influenced weather, silver iodide is used for catalyzing rainfall (cloud seeding). During this process, one gram of silver iodide produces tens of trillions of ice crystals in cold clouds that help to precipitate raindrops. It is also used to treat sandstorms, hailstorms and fog.
Silver iodide is found in nature in the mineral odargyrite and is extracted by reacting it with concentrated hydriodic acid under ruby red light. It is also prepared by reacting iodide solutions (such as sodium or potassium iodide) with silver nitrate (AgNO3), allowing the solution to precipitate as b-AgI. It is further reacted with iodine in aqueous solution to form a-AgI, which can then be purified by precipitation under a vacuum. The toxicity of silver iodide can be minimized by using it under well-ventilated conditions, wearing gloves and a lab coat, and avoiding eye contact. If poisoning is suspected, seek immediate medical attention.