In the late 18th century what was the term "dephlogisticated" applied to?

Question

In the late 18th century, Pennsylvania built a presidential palace in a futile effort to have Philadelphia made the permanent national capital. What happened to it?

Answer 1

Air
English philosopher and chemist Joseph Priestley isolated what he called "dephlogisticated air" in 1774. Early western chemical theory was that phlogiston is released when a substance was burnt, that the released phlogiston is absorbed by the air, then absorbed by growing plants which is why air does not spontaneously combust and why plant matter burns. The "dephlogisticated air" Priestley isolated was oxygen.