Pearly Whites

Fact: Pearls dissolve in vinegar.

Pearls are as solid as rocks, but drop your necklace in a glass of vinegar and watch your favourite pearls melt away before your eyes.

It might seem outlandish, but really its just simple chemistry. The trick is that pearls are simply calcium carbonate crystals (or CaCO3, if you’re feeling academic this afternoon). This means that when they react with vinegar – which is acetic acid, or CH3COOH – in a very standard, GCSE chemistry salt + acid reaction:

2 CH3COOH  +  CaCO3   –>  Ca(CH3COO)2 + H2O + CO2

The salt formed (calcium acetate) is, unlike calcium carbonate, soluble. This means that as the reaction happens the solid pearl dissolves away, leaving nothing but a sense that perhaps you should have performed this experiment on something a ltitle less expensive.

‘Another one of Mr Shaunak’s Little Bites of Science’
Image under Creative Commons license


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