======Golden Rain======


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**Materials: **{{$demo.materials_description}}\\
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**Safety: **{{$demo.safety_description}}\\
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**Alternative titles:** Lead Iodide Precipitation
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====Summary====                   
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====Procedure====  
  - Dissolve 1.65 g of lead(II) nitrate in 400 mL of distilled water in one beaker.  
  - Dissolve 1.66 g of potassium iodide in 400 mL of distilled water in another beaker.  
  - Combine the two solutions in a flask (about 800 mL total). A yellow precipitate of lead iodide forms immediately.  
  - Heat the mixture to about 80 °C, stirring until all the lead iodide dissolves.  
  - Allow the flask to cool slowly. As it cools, brilliant golden-yellow crystals of lead iodide form and fall, creating the golden rain effect.  
  - For best viewing, place the flask where bright sunlight can shine through it against a dark background.



====Links==== 
Golden Rain - mrhomescientist: 
{{youtube>4xSUvSGywXo?}}\\


📄 Golden Rain Experiment - Chem Talk: [[https://chemistrytalk.org/lead-iodide-reaction/]]\\


====Variations====
  * Repeat the experiment with smaller volumes for a quicker classroom demo.  
  * Place the flask on a magnetic stirrer during cooling to keep crystals suspended longer.  
  * Compare the rapid precipitation of PbI₂ at room temperature with the slower, more ordered crystallization upon cooling.



====Safety Precautions====
  * Lead nitrate and lead iodide are toxic — avoid ingestion, inhalation, and skin contact.  
  * Always wear safety glasses, gloves, and a lab coat.  
  * Perform the experiment in a well-ventilated lab or fume hood.  
  * Do not dispose of lead salts down the drain. Collect precipitates for proper hazardous waste disposal.  
  * Keep all lead compounds away from food and student handling.




====Questions to Consider====
  * Why does lead iodide precipitate immediately when the two salts are first mixed? (PbI₂ is insoluble in cold water.)  
  * Why does heating dissolve the precipitate? (The solubility of PbI₂ increases with temperature.)  
  * Why does crystallization produce hexagonal plate-like crystals? (PbI₂ has a hexagonal crystal lattice structure.)  
  * What would happen if excess iodide ions were added? (A soluble plumbate complex, [PbI₄]²⁻, could form instead of PbI₂ precipitating.)  
  * Why must lead salts be disposed of carefully? (They are toxic and harmful to the environment.)