Alcahest

In Renaissance alchemy, alkahest was the theorized "universal solvent". It was supposed to be capable of dissolving any composite substance, including gold, without altering or destroying its fundamental components. By extracting from composite substances their fundamental virtues and properties, alchemists hoped to gain control of invaluable medical healing properties. For this reason the alkahest was earnestly sought. At the same time, its very existence was debated among alchemists and philosophers.