Granted Patent
Utility
US 4,804,526 · App. 07/107,329
Process for purifying phosphoric acid for electrical semiconductor use
Inventors:
Richard E. Hall, Peter H. Zeh, Frederic B. Jueneman
Patented Case
View Patent ↗
Granted: Feb 14, 1989
Filed: Oct 13, 1987
Inventors
Richard E. Hall
Peter H. Zeh
Frederic B. Jueneman
Assignee (at issue)
FMC CORPORATION
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.