, should be replaced by the expression
, where
is the mass of a molecule. The reason for this substitution is found in the fact that the magnitude of the constructed-volume element
varies with time due to the variation of velocities effected by molecular collisions. Now this variation of magnitude is not permissible with the probability considerations which here obtain. For the probability of a state which necessarily follows from another state must be like that of the latter. As the momenta after collision are the same as before collision, we have now in the momenta, co-ordinates which do not vary with time like their constituent velocities. Therefore if we substitute in (12) for the velocities
their corresponding momenta, the variation with time of the constructed-volume will cease and the objection cited will no longer be a valid one.
Now let us take up the determination of the number of complexions