Lead iodide

Lead(II) iodide or lead iodide is a salt with the formula PbI2. At room temperature, it is a bright yellow odorless crystalline solid, that becomes orange and red when heated. It was formerly called plumbous iodide. Lead(II) iodide or lead iodide is a salt with the formula PbI2. At room temperature, it is a bright yellow odorless crystalline solid, that becomes orange and red when heated. It was formerly called plumbous iodide. The compound currently has a few specialized applications, such as the manufacture of solar cells and X-ray and gamma-ray detectors. Its preparation is a popular demonstration in basic chemistry education, to teach topics such as double displacement reactions and stoichiometry. It is decomposed by light at moderately high temperatures and this effect has been used in a patented photographic process. Lead iodide was formerly employed as a yellow pigment in some paints, with the name iodide yellow. However, that use has been largely discontinued due to its toxicity and poor stability. PbI2 is commonly synthesized via a double displacement reaction between potassium iodide KI and lead(II) nitrate Pb(NO3)2 in water solution: While the potassium nitrate KNO3 is soluble, the lead iodide PbI2 is nearly insoluble at room temperature, and thus precipitates out. Other soluble salts containing lead(II) and iodide can be used instead, for example lead(II) acetate and sodium iodide. The compound can also be synthesized by reacting iodine vapor with molten lead between 500 and 700 °C. A thin film of PbI2 can also be prepared by depositing a film of lead sulfide PbS and exposing it to iodine vapor, by the reaction The sulfur is then washed with dimethyl sulfoxide.