Lead Iodide Complex Salts

Lead iodide combines with hydriodic acid to form a crystalline compound, and with a large number of metallic iodides to form double salts.

The compound HI.PbI₂.5H₂O is obtained in unstable crystals by the action of hydriodic acid on lead in presence of air, or by dissolving lead iodide in hydriodic acid; and the following double iodides have been described: PbI₂.2LiI.4H₂O, PbI₂.LiI.5H₂O, PbI₂.4NaI, PbI₂.2NaI.4H₂O, PbI₂.2NaI.6H₂O, PbI₂.KI.2H₂O (other potassium salts have been described, but their existence is doubtful), 3PbI₂.4NH₄I.6H₂O, 3PbI₂.4N(CH₃)₄I, PbI₂.RbI.2H₂O, PbI₂.CsI; also double iodides containing the following elements: Mg, Ca, Sr, Ba, Zn, Cd, Sn, Cr, Fe, Mn, Ni, Co, Al, P, As, Sb, Bi. The pyridine compounds PbI₂.2C₅H₅N and PbI₂.3C₅H₅N have been prepared.

The following chloriodides PbI₂.PbCl₂ or PbICl and 3PbICl.H₂O, and the bromiodide PbI₂.3PbBr₂ are said to exist, but it is questionable whether they are true compounds or isomorphous mixtures of the different halides.