For any valid study of reaction kinetics the phase equilibria involved must, be known. We present an apparatus designed to measure both phase equilibria and kinetics for reactions in near-critical water. Liquid-liquid mutual solubilities are reported for the benzene-water and toluene-water systems from 200 to 275 degrees C at the three-phase pressures and 172 bar. These data were found to be in good agreement with data reported in the literature. Additionally, the near-critical water reaction apparatus was used to verify one-phase regions for the phenol-water and p-cresol-water systems from 250 to 300 degrees C at 172 bar.