  We derive a formula for the dry adiabatic lapse rate of atmospheres composed
of real gases. We restrict our study to those described by a family of
two-parameter cubic equations of state and the recent Guevara non-cubic
equation. Since our formula depends on the adiabatic curves, we compute them
all at once, considering molecules that can move, rotate, and vibrate, for any
equation of state. To illustrate our results, we estimate the lapse rate of the
troposphere of Titan, obtaining a better approximation to the observed data in
some instances, when compared to the estimation provided by the virial
expansion up to third order.
