An alternative rigorous expression for the limiting current in reverse pulse polarography (RPP) under semi-infinite diffusion of the amalgamated product inside the spherical electrode is presented, together with comparison of previously reported expressions. For typical parameters (radius 0.02 cm, drop time 1 s, pulse time 50 ms) the neglecting of the sphericity can introduce errors of around 27% in the limiting current value and the error increases with decreasing drop radius and increasing drop time. Some approximations (from literature and newly found) lead to very simple and accurate expressions which are then compared. RPP is shown to be particularly suitable for determining the stability constant in metal-macromolecule complexation within the excess ligand framework, as complex adsorption does not affect the limiting current. Inclusion of sphericity on the normalised limiting current is straightforward and an error of around 8% in the planar normalised current is found for typical parameters in macromolecular systems. Two simple approximate expressions to account for sphericity yield sufficiently accurate estimates (under 1%) of the normalised current for these typical cases. A spherically corrected normalised current, which allows the fitting of the stability constant with the same procedure as usually carried out assuming planar diffusion, is presented.