  In this paper we analyze the energy evolution of the muon content of air
showers between $10^{18.4}$ and $10^{19.6}$ eV to be able to determine the most
likely mass composition scenario from future number of muons measurements. The
energy and primary mass evolution of the number of muons is studied based on
the Heitler-Matthews model and Monte Carlo simulation of the air shower. A
simple model to describe the evolution of the first and second moments of
number of muons distributions is proposed and validated. An analysis approach
based on the comparison between this model's predictions and data to
discriminate among a set of composition scenarios is presented and tested with
simulations. It is shown that the composition scenarios can be potentially
discriminated under the conditions imposed by the method. The discrimination
power of the proposed analysis is stable under systematic changes of the
absolute number of muons from model predictions and on the scale of the
reconstructed energy.
