.. _gas_const_sec: Gas constant value properties ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ An example to define a gas with constant properties is given below: :: EOS GAS SURFACE_DENSITY 1.87 kg/m^3 FORMULA_WEIGHT 44.0 g/mol DENSITY CONSTANT 11.00 !defaults to kmol/m3, unit cannot be specified. VISCOSITY CONSTANT 0.0395 cP ENTHALPY CONSTANT 1.8890d0 J/kmol END Except for Density, the units are optional. If not entered they will take the following defaults: * enthalpy units : :math:`J/k\mbox{mol}` * viscosity units : :math:`Pa.s` * density units are :math:`\mbox{kmol}/m^3`, and units cannot be specified.