Berthelot equation of state

$kT=\left(p+{\frac {a}{Tv^{2}}}\right)\left(v-b\right)$

where Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle a} is an empirical constant.