It is found, for pressures ∼ 1 atm and above, that the residence time for molecular oxygen, in the gas‐phase combustion region surrounding a 525‐&mgr; zirconium droplet, is of the same order of magnitude or greater than the mean dissociation time for molecular oxygen; therefore, the concentration of species are assumed to have their equilibrium values. The distribution of species over the reaction zone is calculated by means of free‐energy minimization. Calculation of the existing equilibria, under known reaction conditions, illustrates the existence or nonexistence of condensed phases. The meanings of reactive collision probability, apparent over‐all oxygen incorporation probability and minimum fractional surface oxygen incorporation, as related to droplet combustion, are discussed. Additionally, some methods by which the maximum combustion temperature of the Zr‐oxygen system has been obtained are discussed.