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Precipitation of Lead Iodide

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

  1. Fill a large flask two-thirds full with water and heat to boiling.
  2. Add solid lead iodide, small ammounts at a time until no-more will dissolve
  3. Stopper the flask and allow to cool.
  4. Observe that upon cooling, yellow crystals of lead iodide form throughout the flask and eventually fall to the bottom in a golden shower.
Notes:
  1. The solubility of lead iodide is 0.41 g/100ml in hot water, and 0.044 g/100ml in cold water.
  2. You can of course speed up the reaction by cooling the flask. (Note - I have found that dropping ice into the flask causes the best reaction).
  3. The cooled flask can be stoppered and re-used many times by reheating the solution to boiling to redisolve the crystals.

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Last Updated: 5/23/02