Granted Patent
Utility
US 4,249,990 · App. 06/026,204
Process for removal of potassium values from pulp mill liquors
Inventors:
Allan Gilbert, W. Howard Rapson
Patented Case
View Patent ↗
Granted: Feb 10, 1981
Filed: Apr 2, 1979
Inventors
Allan Gilbert
W. Howard Rapson
Assignee (at issue)
ERCO Envirotech Ltd.
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.