Nevertheless, the computation is much easier with this reduced equation.
2.
If on the other hand d \ rho / ds is not identically 0, then its zeroes are isolated and the reduced equations can be combined to yield the orbital equation
3.
Its essential feature is that if we scale the thermodynamic variables that describe an equation of state ( temperature, pressure, and volume ) with respect to their values at the liquid-gas critical point, all simple fluids obey the same reduced equation of state.