Lavoisier proposes silica as an oxide of an unknown element

Background. Antoine-Laurent de Lavoisier was a French nobleman and chemist central to the 18th-century chemical revolution, noted for establishing oxygen's role in combustion against phlogiston theory and for shifting chemistry from a qualitative to a quantitative science. By 1787 he was engaged in reforming chemical nomenclature, a context in which his conjecture about silica emerged.

The Proposal on Silica. In 1787 Lavoisier suspected that silica might be an oxide of a fundamental chemical element. Silicon's strong chemical affinity for oxygen meant he had no means of reducing the oxide to isolate the element, so the substance remained hypothetical. He also predicted the existence of silicon in his first extensive list of elements, dated 1787.

Nomenclature Context. The proposal coincided with the nomenclature reform Lavoisier submitted to the academy in 1787 with Louis-Bernard Guyton de Morveau, Claude-Louis Berthollet, and Antoine François de Fourcroy. Their Méthode de nomenclature chimique, published in Paris by Chez Cuchet, tied naming to Lavoisier's oxygen theory; its list of earths described them as oxides of yet unknown metals.