A flask containing a hot solution of lead iodide is prepared. As the solution cools, crystals of lead iodide form and fall to the bottom of the flask.
Procedure Fill a large flask two-thirds full with water and heat to boiling.
Add solid lead iodide, small ammounts at a time until no-more will dissolve Stopper the flask and allow to cool. Observe that upon cooling, yellow crystals of lead iodide form throughout the flask and eventually fall to the bottom in a golden shower. You can of course speed up the reaction by cooling the flask. The cooled flask can be stoppered and re-used many times by reheating the solution to boiling to redisolve the crystals.