Granted Patent
Utility
US 4,938,854 · App. 07/276,615
Method for purifying quaternary ammonium hydroxides
Inventors:
Hossein Sharifian, Alan R. Tanner
Patented Case
View Patent ↗
Granted: Jul 3, 1990
Filed: Nov 28, 1988
Inventors
Hossein Sharifian
Alan R. Tanner
Assignee (at issue)
Southwestern Analytical Chemicals, Inc.
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.