Granted Patent
Utility
US 4,581,220 · App. 06/541,121
Process for the extraction of metal values and novel metal extractants
Inventors:
Anthony J. Nelson, Peter M. Quan, David Stewart
Patented Case
View Patent ↗
Granted: Apr 8, 1986
Filed: Oct 12, 1983
Inventors
Anthony J. Nelson
Peter M. Quan
David Stewart
Assignee (at issue)
IMPERIAL CHEMICAL INDUSTRIES LIMITED
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.