Thermodynamics Research Center / ThermoML | Fluid Phase Equilibria

ABSTRACT

The solubilities of ternary system Na2SO4-CO(NH2)2-H2O and MgSO4-CO(NH2)2-H2O and quaternary system Na2SO4-MgSO4-CO(NH2)2-H2O at 60 C were measured by isothermal method, and the corresponding phase diagrams were studied. There are five crystalline fields in the quaternary system Na2SO4-MgSO4-CO(NH2)2-H2O at 60 C, which correspond to MgSO4.6H2O, Na2SO4.MgSO4.4H2O, Na2SO4, CO(NH2)2 and MgSO4.CO(NH2)2.4H2O respectively. On the basis of the analyses of the phase diagram of the quaternary system Na2SO4-MgSO4-CO(NH2)2-H2O at 60 C and 25 C, Na2SO4 and Mg - N compound fertilizers can be produced using CO(NH2)2 as salting-out agent directly. On the basis of the extended Pitzer model of electrolyte solution theory, the solubilities of Na2SO4-MgSO4-CO(NH2)2-H2O system at 60 C were calculated. The results showed that calculated values were well consistent with experimental results.