Granted Patent
Utility
US 3,939,248 · App. 05/250,601
Process and apparatus for manufacturing phosphoric acid
Inventor:
Harold B. Caldwell
Patented Case
View Patent ↗
Granted: Feb 17, 1976
Filed: May 5, 1972
Inventor
Harold B. Caldwell
Assignee (at issue)
Whiting 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.