A yellow precipitate formed on adding $\mathrm{Pb}(\mathrm{NO}{}_3){}_2$ to a colourless solution dissolves on boiling, and golden-yellow spangles separate on cooling. The precipitate is

$\mathrm{PbI}{}_2$ is considerably more soluble in hot water and recrystallises as golden spangles on cooling. The other yellow solids ($\mathrm{PbCrO}{}_4$, $\mathrm{AgI}$, $\mathrm{CdS}$) do not dissolve in boiling water. The test confirms iodide.