  The paper introduces the isotopic Foldy-Wouthuysen representation. This
representation was used to derive equations for massive interacting fermion
fields. When the interaction Hamiltonian commutes with the matrix, these
equations possess chiral invariance irrespective of whether fermions have mass
or are massless. The isotopic Foldy-Wouthuysen representation preserves the
vector and axial currents irrespective of the fermion mass value. In the Dirac
representation, the axial current is preserved only for massless fermions. In
the isotopic Foldy-Wouthuysen representation, the ground state of fermions
(vacuum) turns out to be degenerate, and therefore there is the possibility of
spontaneously breaking parity (P - symmetry). This study considers the example
of constructing a chirally symmetric quantum electrodynamics framework in the
isotopic Foldy-Wouthuysen representation. A number of physical processes are
calculated in the lowest orders of the perturbation theory. Final results of
the calculations agree with the results of the standard quantum
electrodynamics.
