GOLDEN RAINThis experiment is based on an instantaneous chemical reaction known as “Gold Reaction”. The bright yellow precipitate is formed by mixing the solutions containing lead(II) ions and iodide ions.

Pb(NO3)2 + 2 KI ------> PbI2 + 2KNO3

HOW TO DO THIS ?

Two solutions need to be prepared in advance. These are 0.3 wt.% solutions of potassium iodide and lead nitrate. The solutions need to be made strictly in distilled water and make sure that both the solutions should be perfectly colourless before mixing.

Now mix approximately equal volumes of KI and Pb(NO3)2 solutions in a flask and allow to settle. As a result of this, the lead iodide will precipitate out and get settled at the bottom of flask.

Now decant off the supernatant liquid ( mother liquior) and add the wet precipitate to a similar volume of hot water (70 – 80C) acidified with a little glacial acetic acid in a round bottomed flask. The precipitate will quickly dissolve.

Now allow the solution to cool down. After the flask is cooled (under a stream of cold water) beautiful shiny golden crystals begin to form; these slowly fill the flask. If the lamp is allowed to shine on the flask against a black background the crystallisation process appears to the viewers as “golden rain” in a blaze of beautiful

Colour. The effect is even better if room is darkened.

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