Speed of Sound Measurements and a Fundamental Equation of State for Hydrogen Chloride

A fundamental equation of state in
terms of the Helmholtz energy
is presented for hydrogen chloride. Any thermodynamic property can
be calculated by combinations of its derivatives with respect to the
independent variables temperature and density. The present equation
of state is applicable in the entire fluid region. Its accuracy is
assessed by comparison with the available experimental literature
data from the triple point temperature to 480 K and a maximum pressure
of 40 MPa. A reasonable extrapolation behavior beyond these temperature
and pressure limits is ensured to allow for an application to mixture
models. For the development of the present equation of state, speed
of sound measurements are carried out in the liquid and dense vapor
phases by means of the pulse-echo technique. Because no speed of sound
measurements for this fluid are reported in the literature, the present
experimental data set is crucial for the accurate modeling of caloric
properties of hydrogen chloride.