A New High Temperature Phase Equilibrium Apparatus for Water-salts System

Based upon the needle value technique devised by Waldeck, Lynn and Hill, a new phase equilibrium apparatus for high temperature water-salts system with an inner liquid sampler and an inner detached solid sampler was designed and manufactured. The operating method of the apparatus was described in detail. To validate the credibility of the experiment equipment at acquiring solubility data, an invariant point of the phase diagram of the system NaOH-Na2CO3-H2O at 150oC with the equilibrium solid pairs Na2CO3 vs NaOH, and an invariant point of the phase diagram of the system Na2CO3-NaHCO3-H2O with the equilibrium solid pairs Na2CO3 vs NaHCO3•Na2CO3•2H2O were measured, respectively, and the obtained data were in relative agreement with those reported in corresponding references. Data repeatability tests for the experimental equipment and the investigating method were of small coefficient of variation.