The speed of sound of $n$-heptane, $n$-octane and their binary mixtures at temperatures $T=293.15$ to $523.15$ K and pressures up to $60$ MPa

Speeds of sound in liquid $n$-heptane, $n$-octane and their binary mixtures were measured at the temperatures $T=293.15$ to $523.15$ K and pressures up to $60$ MPa. The pulse-echo method with a frequency of $8$MHz and uncertainty of $\pm0.08\%$ was used. The measured values were fitted by polinomials, as functions of temperature and pressure, and the reliability of the present results was proved by comparison with the literature data.