Lead (II) Iodide Lead iodide, lead diiodide, or Plumbous iodide with the formula PbI₂ is often sold in a powder or crystal form and has a formula weight of 461.01g/mol. It is an ionic compound, consisting of two halogens (iodide) and one post-transition metal (lead). Following chemical solubility rules, it is insoluble in water and also denser than water. It has very high melting and boiling points of 402°C and 954°C respectively. It is extremely hazardous to human health (due to the lead content) as well as the aquatic environment. It’s color ranges from yellow, to yellow-orange, to orange-brown. It is also odorless and non-combustible.