[ANON POST] Persuading Lavoisier that Sapphire Is an Element
I'm writing a story part of which is set in 18th Century Paris shortly after Lavoisier's publication of Méthode de nomenclature chimique. One of my characters wants to convince Lavoisier that Sapphire is an element. They do not need to succeed but I'd like an idea of the evidence they might put forward and how (and if) Lavoisier might counter it. The character isn't a scientist but is a lady of leisure with an interest in current developments in science.
For instance, I'm unclear whether people would have been aware, at the time, that Sapphire was an oxide (or at least decomposable - because contemporary confusions about oxygen). Might Lavoisier have been aware but an interested lay person not aware?
Basically I'm looking for a plausible for circa 1790 argument that Sapphire is an element that is framed with reference to Lavoisier's treatise.
I've read the wikipedia pages on Lavoisier, Sapphire, Corundum and Chemical Nomenclature. I've searched on "Méthode de nomenclature chimique", "Sapphire history", "Sapphire history chemistry", "Corundum History"
