“Golden rain” experiment
How to obtain shiny “golden” crystals
When a hot solution of lead iodide cools down, the salt settles in beautiful golden particles.
Wear protective glasses and gloves. Lead compounds are very poisonous! Don’t swallow the salts and solutions! Follow general safety recommendations. Chemical experiments must be carried out in full compliance with the legislation of your country.
Warning! Do not try this at home. Only under professional supervision.
Reagents and equipment:
- lead nitrate (0.3 g );
- potassium iodide (0.3 g);
- acetic acid (~1-2 ml);
- distilled water (500 ml);
- three beakers;
- cuvette 50 ml.
In different beakers, dissolve lead nitrate and potassium iodide in small quantities of water (5 ml) Add a little acetic acid to the solution, to prevent its hydrolysis. Heat the remaining distilled water to ~80°С. Mix the solutions of lead nitrate and potassium iodide in a cuvette. A yellow sediment forms. Add hot water until the sediment dissolves completely. Let the solution cool. When it cools, beautiful gold crystals of lead iodide begin to settle.
When the solutions of the two salts are mixed, an exchange reaction takes place:
Pb(NO₃)₂ + 2KI → PbI₂↓ + 2KNO₃
The forming lead iodide is insoluble in cold water, but at a high temperature its solubility increases. So in a hot solution, precipitation is not observed. When the mixture cools, the solubility of lead iodide decreases, and Pbl₂ crystals gradually begin to settle, which resemble golden flakes.