Assertion: arsenic's compound | /r/ObjectUse | used in the manufacture of felt hats
Facets:
value: in the 18th and 19th century
type: TEMPORAL
Source sentences:
text: The phrase "mad as a hatter" is likely a reference to mercury poisoning among milliners (so-called "mad hatter disease"), as mercury-based compounds were once used in the manufacture of felt hats in the 18th and 19th century.