Process for producing aryldiazonium salts from nitrogenous gases rich in nitrogen oxide, aqueous solutions of these salts and their use for the preparation of aminoazoaromatic compounds

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

Why it's free to use

• Filed February 23, 1979 and granted April 1, 1981. A European patent lasts at most 20 years from filing, so its term ended February 23, 1999.
• A supplementary protection certificate, which can extend a medicine or crop-protection patent, adds at most five and a half years, so even that would have ended by August 23, 2004.
• We check European rights only. A US or other national patent in its family could still be in force: check its family on Espacenet or Google Patents.