The equation proposed earlier has been derived from a new kinetic concept. It is shown to be a reasonable approximation of this new consideration. The equation is also shown to be mathematically consistent with the general fact that when the thermomolecular pressure difference is plotted against the normally measured pressure, a single maximum is obtained. The curves calculated from this equation are shown to agree closely with those from the Weber equation using van Itterbeek and de Grande's data. The practical use of the equation is discussed.