Characterisation of ortho- and meta-boric acids in the vapour phase

Abstract

Vibrational spectroscopy in the vapour phase has shown metaboric acid cyclic trimer in equilibrium with monomeric orthoboric acid and water. An approximately equal amount of boron (1 : 3 mole ratio) is present as (HBO₂)₃ and as H₃BO₃, at 350 °C and a few atmospheres total (water and boric acid) pressure; a condensed phase of widely variable composition is also present. Proportionately very much less trimer is present at the lowest temperatures (just over 100 °C for IR work).