Based on the modified kinetic model of the Landolt and the Dushman reactions published recently, an exact expression has been derived for the concentration dependence of the Landolt time. It is also shown that all the apparently contradictory formulas, regarding the concentration dependence of the Landolt time, reported previously at quite different experimental circumstances can easily be reconciled from the simplification of the newly proposed equation. It also means that the formula derived may satisfactorily be applied to calculate the Landolt time basically with no restrictions for the concentration of the reactants.