Granted Patent
Utility
US 5,116,997 · App. 07/684,874
Purification of indigo
Inventor:
Reinhold Kohlhaupt
Patented Case
View Patent ↗
Granted: May 26, 1992
Filed: Apr 15, 1991
Inventor
Reinhold Kohlhaupt
Assignee (at issue)
BASF SE
This patent predates the USPTO's electronic file wrapper — prosecution documents from this era exist only in the Patent Office's paper records. A certified copy of the file history can be ordered from the USPTO's paper archives.