Specific behavior of acid–base and neutralization reactions in supercritical water

Acid–base and its neutralization behaviors were analyzed with recently reported dissociation constant data determined by electrical conductivity, UV–Vis and pH methods at 400 °C and densities ranging from 0.3 to 1.0 g/cm3. The systems are HCl, HNO3, H2SO4, phenol, β-naphthol, β-naphthoic acid, NH4OH, alkali metal hydroxides and alkali metal chlorides. Among these systems, HCl and KOH are strongest acid and base, respectively. Then neutralization behaviors of HCl+NaOH, dissociation behavior of NaCl and titration behavior of HCl+LiCl and LiOH+LiCl were studied with dissociation constant data and activity coefficient formulation. The results gave informations that (1) the equivalence point for neutralization was placed at a little smaller NaOH concentration than initial HCl concentration, (2) NaCl solution behaved as a base, (3) H+ and OH− molalities in HCl and LiOH solutions, respectively, were decreased with increasing LiCl concentration.