text: Phosphinous acid (or Phosphinol) is the inorganic compound with the formula HPOH. It exists, fleetingly, as a mixture with its less stable tautomer HPO (phosphine oxide).  This mixture has been generated by low temperature oxidation of phosphine with ozone. HPOH is mainly of pedagogical interest.  Organophosphinous acids are more prevalent than the parent HPOH.