Granted Patent
Utility
US 4,217,202 · App. 05/958,673
Process for selective recovery of relatively metals-free bitumen from tar sand using a halogenated aliphatic solvent in combination with a second solvent
Inventors:
John A. Paraskos, Edward W. Smith
Patented Case
View Patent ↗
Granted: Aug 12, 1980
Filed: Nov 8, 1978
Inventors
John A. Paraskos
Edward W. Smith
Assignee (at issue)
Gulf Research & Development Company
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.