In his Natural History, Roman natural philosopher, Pliny the Elder, described a decadent dinner thrown by Cleopatra for Antony. According to Pliny (NH 9:58), Antony had feted the Egyptian Queen with many sumptuous dinners, and Cleopatra had begun turning her nose up at his attempts to impress her. Cleopatra made a wager with Antony that she could spend “10 millions of sesterces” at the next dinner, an exorbitant amount.
The next day, Cleopatra sat Antony at her dinner, but Antony noted that it was very nearly the same offerings as at his previous dinners.
He wondered to Cleopatra where she
could have possibly spent the millions of sesterces.
Cleopatra, pleased that Antony had taken her bait, ordered the next course, a cup of vinegar. Cleopatra then took one of her enormous pearl earrings from her ear and dissolved it in the vinegar.
Then she drank it.
The pearl earrings were made from the two largest pearls known to the world at the time. After Antony and Cleopatra’s defeat at the Battle of Actium by Octavian’s (later Caesar Augustus) forces, the other pearl was taken and split into two, where it served as the earrings for the statue of Venus in Rome’s Pantheon.
The question of whether a pearl could be dissolved in vinegar has long been a matter of scholarly debate up through the twenty-first century. For years, scholars have cast doubt on the veracity of the entire story, claiming that such a thing was impossible. In 2010, classicist Prudence J. Jones published the chemical formula for the reaction that shows that pearls do indeed disintegrate completely in vinegar. D. Fatta‐Kassinos of Cyprus is credited with providing the formula:
CaCO3 + 2CH3COOH -> Ca + 2CH3COO- + H2O+CO2
Jones explains, “Pearls are made up of calcium carbonate therefore the reaction between a pearl and vinegar is an acid–base reaction and vinegar would, as Pliny describes, destroy a pearl. The calcium carbonate in a pearl reacts with the acetic acid (vinegar) to produce calcium acetate, water, and carbon dioxide.”
Idea contributed by Lesley Lundeen, Chicago.
Discussion with Dr. Prudence Jones: Pearls, Chemistry, and Citation Bias
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Secondary Sources:
Prudence J. Jones, “Solution to Cleopatra's Cocktail challenge,” Analytical and Bioanalytical Chemistry (2011) 399:2307. Published online: 30 December 2010.