  We analyze the electromagnetic contributions to the octet and decuplet baryon
masses using the heavy baryon approximation in chiral effective field theory
and methods we developed in earlier analyses of the baryon masses and magnetic
moments. Our methods connect simply to Morpurgo's general parametrization of
the electromagnetic contributions and to semirelativistic quark models. Our
calculations are carried out including the one-loop mesonic corrections to the
basic electromagnetic interactions, so to two loops overall. We find that to
this order in the chiral loop expansion there are no three-body contributions.
The Coleman-Glashow relation and other sum rules derived in quark models with
only two-body terms therefore continue to hold, and violations involve at least
three-loop processes and can be expected to be quite small. We present the
complete formal results and some estimates of the matrix elements here.
Numerical calculations will be presented separately.
