Isohyrores on the phase diagrams of multicoponent salt-water systems are often necessary in technological design. We obtained 650 points on isohy-drores at 25℃ for Na+
K+
Mg2+/Cl--H2O
2Na+
Mg2+/2Cl-
SO42--H2O systems by using Pitzers theory of electrolyte solution. These data are useful in estimating saturation point of salt of brine