  The change in the fluxes of the lightest and heaviest nuclei in the mass
composition of primary cosmic radiation in the energy range of E0 = 1-100 PeV
is analyzed on the basis of data from the KASCADE-Grande experiment. This
analysis is performed by means of the min-max age (Smin-max) method for
extensive air showers (EAS) that is proposed in the present article. This
method makes it possible to estimate the exponents of the spectra for the
lightest and heaviest nuclei in the mass composition of primary cosmic
radiation and to study irregularities in these spectra at energies E0 in the
range under consideration. The Smin-max method for estimating the mass
composition of primary cosmic radiation is based on a sizable sample (more than
100 million events) of data on EAS features in the range of E0 = 1-100 PeV from
the KASCADE-Grande experiment. It is shown that, in the primary-energy range of
E0 = 1-100 PeV, the exponent in the integrated spectrum changes from 2.1 to 2.7
for the lightest nuclei in the mass composition of primary cosmic radiation and
from 1.5 to 2.1 for the heaviest nuclei. These results comply with the
conclusion drawn by the KASCADE-Grande Collaboration that the knee in the E0
spectrum of nuclei of primary cosmic radiation in the range of E0 = 3-5 PeV is
due to the elimination of light nuclei. The bump appearing in the E0 spectrum
of primary cosmic radiation according to the database of the KASCADE-Grande
experiment and lying in the range of E0 = 50-75 PeV is analyzed by the Smin-max
method and is found to agree with data of the GAMMA (GAMMA-07) experiment.
