In the paper “Re-evaluation of activities of magnesium and zinc components in the magnesium–zinc binary system from very low to high temperature” by Morishita et al. , which recently appeared as a Feature Article in this journal, the authors made the following three statements, commencing with the first sentence of the abstract: 1. The activities of zinc, a Zn , and magnesium, a Mg , from very low to high temperatures in the Mg–Zn binary system were evaluated for the first time from the relationship between the Gibbs energies of formation, Δ f G ° T , of Mg 48 Zn 52 , Mg 2 Zn 3 , MgZn 2 and Mg 2 Zn 11 and their phase equilibria.” 2. It was found that the a Zn and a Mg values in the compounds steeply changed from the minimum to maximum as a function of the composition in a narrow solubility range.” 3. “…at very low temperatures, a Zn and a Mg were very small approaching to zero, …”; “The values of log a Zn and log a Mg in the two-phase regions were found to be decreased … and resulted in very small values”. These three statements are disputed and commented below. For convenience, let us start with the second statement.