ABSTRACT
Why did transmutation of metals seem plausible at that time? This was long before the atomic theory of matter was accepted, and so the word 'element' had a different meaning. All substances were supposed to be made of various proportions of the four Aristotelian 'Elements' - Air, Earth, Fire, Water (see Fig. 11.1, p. 69). But Aristotle meant principles, or properties, rather than elements in the modern chemical sense. Proportions of (tenuous) airy, earthy, hot and humid characteristics were seen as imposed on a central prima materia. It was a familiar observation that substances changed into other substances, such as earth becoming fruit. But as it was incorruptible, gold had a special status making it uniquely hard to transmute. It was known well before the seventeenth century that gold could be dissolved by ordinary - not magical or 'philosophic' - aqua regia, a mixture of nitric and hydrochloric acids. It was thought, however, that this did not change the essential nature of the gold, but dissolved it essentially unchanged into small particles. Great efforts went into dissolving gold for transmutation. Robert Boyle would quote the alchemical saying: 'It is harder to destroy gold than make it.'
