Boyle and the Definition of an Element.
§ 73. Robert Boyle (1626-1691) had defined an element as a substance which could not be decomposed, but which could enter into combination with other elements giving compounds capable of decomposition into these original elements. Hence, the metals were classed among the elements, since they had defied all attempts to decompose them. Now, it must be noted that this definition is of a negative character, and, although it is convenient to term “elements” all substances which have so far defied decomposition, it is a matter of impossibility to decide what substances are true elements with absolute certainty; and the possibility, however faint, that gold and other metals are of a compound nature, and hence the possibility of preparing gold from the “base” metals or other substances, must always remain. This uncertainty regarding the elements appears to have generally been recognised by the new school of chemists, but this having been so, it is the more surprising that their criticism of alchemistic art was not less severe.