We propose two experimental schemes to determine and so to realize the
Avogadro constant N_A at the level of 10−7 or better with a watt
balance experiment and a cold atom experiment measuring h/m(X) (where h is
the Planck constant and m(X) the mass of the atom X). We give some
prospects about achievable uncertainties and we discuss the opportunity to test
the existence of possible unknown correction factors for the Josephson effect
and quantum Hall effect