Compressibility of liquid FeS measured using X-ray radiograph imaging

•We apply in-situ X-ray radiograph technique to liquid density measurement at HP.•Density of liquid FeS was measured at 1650K and pressures up to 5.6GPa.•The isothermal bulk modulus of liquid FeS was derived from the EOS data.•The bulk modulus of Fe–S liquid system is not linear to its composition.•The bulk modulus of Fe–S liquid vs. composition follows an exponential function. Density of liquid FeS was measured at 1650K and pressures up to 5.6GPa using the X-ray absorption radiograph system of the X17B2 beamline at the National Synchrotron Light Source at the Brookhaven National Laboratory. The experimental data were fitted to the third-order Birch–Murnaghan equation of state to calculate the isothermal bulk modulus (K0) of the liquid, yielding K0=11±3GPa when the pressure derivative of bulk modulus is fixed at 5. Combining this result with those from previous studies on Fe–S liquid system, we suggest an exponential relation between the liquid Fe–S alloy bulk modulus and its sulfur content.