text: Nitric acid is a source of nitric oxide complexes, although the details are obscure.  Probably relevant is the conventional self-dehydration of nitric acid:
  : 2 HNO → NONO + HO
  Nitric acid is used in some preparations of nitroprusside from ferrocyanide:
  : HNO + [Fe(CN)] → [Fe(CN)(NO)] + OH + OCN