Naphthalene sublimation was used to experimentally determine the average mass transfer coefficient in parallel, turbulent flow of air over a flat plate having a step discontinuity. Transfer coefficients were collected for Reynolds numbers ranging from approximately 40 000 to 2 000 000. Data were compared to a semi-empirical relationship based on the 1/n power law. A formulation was devised involving the Schmidt number as an integral part of the solution, thus avoiding Reynolds’ analogy. The Schmidt number exponent and the power profile coefficient were expressed in terms of n, which makes the mass transfer coefficient directly obtainable from the Reynolds number.