We report results of longitudinal (one-dimensional) neutron polarization analysis on polycrystalline bulk Co with an average crystallite size of D = 10 nm. The spin-flip small-angle neutron scattering (SANS) data are analyzed in the approach-to-saturation regime within the framework of micromagnetic theory. In particular, we provide a closed-form expression for the spin-flip SANS cross section [Formula: see text]. From the data analysis, we find a room-temperature value of A = (2.6 ± 0.1) × 10( - 11) J m( - 1) for the exchange-stiffness constant, which agrees well with earlier data.