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

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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. No grant is recorded for it in Canada; had it been granted, its 20-year term would have 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.