Phase diagram calculations require only the differences between the chemical potentials of the involved phases. This makes it possible to use even artificial thermodynamic parameter sets which then have to be corrected by means of additional terms. It is demonstrated that mass spectrometric investigations yield a simpler, but more effective algebraic description of the thermodynamic ternary mixing behavior than the results of previous phase diagram assessments : mass spectrometric measurements in the liquid phase, and in the restricted field of fee-phase in the system Fe-Ni-Cr together with the algebraic descriptions of the three binary boundary systems Fe-Ni, Ni-Cr, and Cr-Fe as reported in previous works make it possible to compute ternary phase equilibria in the system Fe-Ni-Cr, showing better agreement with the experimental phase equilibria data than the assessments as reported by Kundrat and Elliot, Hillert and Qiu, and Lee. Additional advantage of the mass spectrometric determined molar Gibbs energy is that the description of the magnetic contributions Z(k)(alpha,mag)(T,x(alpha)) has been merely reduced to the expressions of the pure species.