Process for the preparation of rare-earth and ammonium twin oxalates, their use in preparing rare-earth oxides, and rare-earth oxides thereof

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Listed from its CIPO record in Patent Yard's archive of Canadian patents past their term. Its claims, description and drawings are in the CIPO record and on Google Patents, and the Claude kit works from them.

Why it's free to use

• Filed November 12, 1991 and granted January 11, 2000. A Canadian patent filed from October 1, 1989 lasts 20 years from filing, so its term ended November 12, 2011.
• A certificate of supplementary protection adds at most two years for a drug, so even that would have ended by November 12, 2013.
• We check Canadian rights only. A patent in its family in another country could still be in force: check its family on Google Patents.