Measurement of the speed of sound in supercritical n-pentane at temperatures from (422.69–653.53) K and pressures from (3.5–10.0) MPa

n -Pentane is one of the main components in many industrial fluids, and is widely used as the fuel. The speed of sound can be used for developing the Helmholtz energy formulation and calculating other thermodynamic properties, which has not been reported yet for supercritical n -pentane. In this paper, the speed of sound in supercritical n -pentane was measured by the Brillouin light scattering (BLS) technique within the temperature limits of (422.69–653.53) K along four isobars at p  = (3.5, 6.0, 8.0, and 10.0) MPa. The relative uncertainty of our BLS experimental system is estimated to be less than 0.6% and the relative uncertainty of the reported speed of sound values is estimated to be 0.85% considering the influence of impurities in the sample. The dependences of the speed of sound on temperature and pressure were also analyzed. At the end, we compared the experimental data with the calculated values from the multiparameter EOS proposed by Span and Wagner and the Modified BWR EOS proposed by J. Ratanapisit and J.F. Ely. The AARD is 1.3% for the multiparameter EOS and 1.5% for the Modified BWR EOS, respectively.