Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Equations of State for n-Hexadecane and n-Docosane



Raffaela Romeo, Eric W. Lemmon


Equations of state for n-hexadecane (C16H34) and n-docosane (C22H46) have been developed as functions of the Helmholtz energy with independent variables of temperature and density. The equations were developed based on experimental values of density, speed of sound, isobaric heat capacity, and vapor pressure. With these equations, all thermodynamic properties of n-hexadecane and n-docosane can be calculated. For n-hexadecane, the uncertainty in vapor pressure is 0.5 %. The uncertainty of the saturated liquid density is 0.05 % from the triple point up to 400 K, and 0.2 % at higher temperatures. The uncertainty in densities is within 0.5 %. The speed of sound and isobaric heat capacity can be calculated within 0.25 %. The uncertainties of the properties calculated with the equation for n-docosane are 5 % for vapor pressure, 0.1 % for saturated liquid density, 1 % for density, 0.5 % and 1 % for speed of sound at atmospheric pressure and higher pressures, respectively, and within 3 % for heat capacity.
International Journal of Thermophysics


equations of state, n-hexadecane, n-docosane, Helmholtz energy, thermodynamic properties


Romeo, R. and Lemmon, E. (2022), Equations of State for n-Hexadecane and n-Docosane, International Journal of Thermophysics, [online],, (Accessed June 22, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created August 5, 2022, Updated November 29, 2022