  We explore the feasibility of estimating primary cosmic ray composition at
ultra high energies from the study of lateral age parameter of Extensive Air
Showers (EAS) at ground level. Using different types of lateral distribution
functions, we fit the particle density of simulated EAS to find the lateral age
parameter. We discuss the chemical composition calculating the merit factor for
each parameter distribution. The analysis considers three different primary
particles (proton, iron and gamma), four different zenith angles (0{\deg},
15{\deg}, 30{\deg} and 45{\deg}) and three primary energies (10^{17.25} eV,
10^{17.50} eV and 10^{17.75} eV).
