In this experiment, we aim to investigate the sound velocities as well as the Equation of State (EOS) of Fe-S alloys at pressures above 300 GPa and temperatures up to several thousands of degrees. Therefore, nuclear inelastic scattering (NIS) and X-ray diffraction (XRD) are planned to be used. Applying the NIS technique brings the advantage of studying the lattice dynamics in order to gain the thermodynamic sample characterization. The measured phonon density of states provides the average Debye phonon velocity (vD), which is necessary to calculate the compressional (vp) and shear velocity (vs) of the material, in combination with the density and bulk modulus obtained by XRD. The measurements and following calculations will allow us to refine the amount of Sulphur in the Earth’s core, to explain its observed seismic parameters.