Lead(II) iodide

Physical properties

Yellow hexagonal crystals; density 6.16 g/cm3; melts at 402°C; vaporizes at 954°C; decomposes at 180°C when exposed to green light; slightly soluble in water (0.44 g/L at 0°C and 0.63 g/L at 20°C); Ksp 8.49x10-9 at 25°C; partially soluble in boiling water (4.1 g/L at 100°C); insoluble in ethanol; soluble in alkalis and alkali metal iodide solutions.

Preparation

Lead diiodide is prepared by mixing aqueous solutions of lead nitrate or lead acetate with an aqueous solution of potassium or sodium iodide or hydriodic acid, followed by crystallization. The product is purified by recrystallization. Pb2+(aq) + 2Iˉ (aq) → PbI2(s).

General Description

A yellow crystalline solid. Insoluble in water and denser than water. Primary hazard is threat to the environment. Immediate steps should be taken to limit spread to the environment. Used in printing and photography, to seed clouds and other uses.

Air & Water Reactions

Slightly water soluble.

Reactivity Profile

Lead(II) iodide has weak oxidizing or reducing powers. Redox reactions can however still occur. The majority of compounds in this class are slightly soluble or insoluble in water. If soluble in water, then the solutions are usually neither strongly acidic nor strongly basic. These compounds are not water-reactive. Light sensitive

Hazard

Lead diiodide is toxic if ingested. The symptoms are those of lead poisoning.

Health Hazard

Early symptoms of lead intoxication via inhalation or ingestion are most commonly gastrointestinal disorders, colic, constipation, etc.; weakness, which may go on to paralysis, chiefly of the extensor muscles of the wrists and less often the ankles, is noticeable in the most serious cases. Ingestion of a large amount causes local irritation of the alimentary tract. Pain, leg cramps, muscle weakness, paresthesias, depression, coma, and death may follow in 1 or 2 days. Contact with eyes causes irritation.

Potential Exposure

Lead iodide is used in bronzing, gold pencils; mosaic gold; printing, and photography

Shipping

UN3288 Toxic solids, inorganic, n.o.s., Hazard Class: 6.1; Labels: 6.1-Poisonous materials, Technical Name Required. UN3077 Environmentally hazardous substances, solid, n.o.s., Hazard class: 9; Labels: 9-Miscellaneous hazardous material, Technical Name Required

Purification Methods

It crystallises from a large volume of water. The solubility in H2O is 1.1% at ~10o, and 3.3% at ~ 100o.

Incompatibilities

Lead iodide has weak oxidizing or reducing powers. Redox reactions can however still occur. The majority of compounds in this class are slightly soluble or insoluble in water. If soluble in water, then the solutions are usually neither strongly acidic nor strongly basic. These compounds are not water-reactive. Light sensitive Contact with oxidizers or active metals may cause violent reaction