Page 88 - Pharmaceutical Analytical Chemistry III
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❑DETERMINATION :

 Phenoldisulphonic acid method :

      OH OH OH

HSO3                                  HSO3                      NO2 KSO3                          NO2

                        + HNO3 H2SO4                                 12 N KOH or
                                                                    Conc. NH4OH

             SO3H                                   SO3H                                SO3K

        2,4-phenol                          6-nitro-2,4-phenol                    Yellow colored
      disulphonic acid                      disulphonic acid                           salt

                                               (Colorless)
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