In this study some thermodynamic parameters including freezing point, boiling point and the
vapor pressure of Urmia Lake salt water were investigated as some important environmentally monitored
physicochemical properties of Urmia Lake. In this regard salt concentration is chiefly responsible for the
modification of the thermodynamic properties of Urmia Lake water which affects its overall environmental
and ecological characteristics. On the other hand, the Urmia Lake is now supposed to be the most convenient
place for many rare aquatic species and therefore interpreted to be unique from the viewpoint of qualitative
characteristics. For the goals of this study water sampling and analysis where performed in two wet and dry
periods of the lake in order to represent the extremes of the lake’s environmental variability. Prevailing
chemical ions in the water body were determined and used for the estimation of the relative thermodynamic
coefficients of salt water for the acquisition of the freezing point, boiling point and the vapor pressure of the
Urmia Lake water. Interpolated calibration curves were plotted for the changes in the studied parameters
versus a variety of salt concentrations indicating a linear relationship between the investigated parameters and
the prevailing salt concentration of the Urmia Lake. The calibration curves were then formulated to simplify
the estimation of the thermodynamic parameters of the Urmia Lake for any salinity conditions. Real sample
analysis also showed a very good agreement between the estimated and observed values.