Chemical Properties
Yellow Crystalline Powder
Physical properties
Light yellow hexagonal crystals or powder; darkens on exposure to light; density 5.68 g/cm3 ; melts at 558°C; vaporizes at 1,506°C; insoluble in water, most acids and ammonium carbonate solution; moderately soluble in concentrated solutions of alkali chloride, bromide, and thiosulfate; readily soluble in solutions of alkali cyanides, iodides and in hot concentrated hydriodic acid.
Definition
T3DB: Silver iodide is an iodide of silver. It is a photosensitive solid used in photography, as an antiseptic in medicine, and in rainmaking. Silver is a metallic element with the chemical symbol Ag and atomic number 47. It occurs naturally in its pure, free form, as an alloy with gold and other metals, and in minerals such as argentite and chlorargyrite.
Preparation
Silver iodide is prepared by adding a solution of sodium or potassium iodide to a hot solution of silver nitrate: Ag+ (aq) + Iˉ (aq) → Ag I (s) The precipitate is washed with boiling water. The preparation is done in the dark under ruby red light.
Hazard
Silver iodide may cause irritation and psoriasis, and the main hazards encountered in the use and handling of silver iodide arise from its toxicological properties. It is toxic by a variety of routes (i.e. inhalation, ingestion and dermal contact) and exposures may include rashes, conjunctivitis, psoriasis (permanent greyish-grey discolouration of the skin, conjunctiva, and internal organs), headache, fever, hypersensitivity reactions, laryngitis and bronchitis.
Health effects
Silver itself is not toxic to humans, but most silver salts are. In large doses, silver and compounds containing it can be absorbed into the circulatory system and become deposited in various body tissues, leading to argyria, which results in a blue-grayish pigmentation of the skin, eyes, and mucous membranes. Argyria is rare, and although, so far as known, this condition does not otherwise harm a person's health, it is disfiguring and usually permanent. Mild forms of argyria are sometimes mistaken for cyanosis.
Flammability and Explosibility
Nonflammable
