The Oxidation of Tin

By means of a vacuum microbalance, the rates of oxidation of pure tin have been determined over a temperature range of 150°–220°C, and for several different pressures of oxygen in the range of 10 −3 mm to 500 mm Hg. For oxygen pressures of 1 mm and above, the oxidation appears to proceed with time in three stages: ( a ) initially, the rate is low, but it increases to a maximum; ( b ) it then decreases and follows a direct logarithmic relationship; and ( c ) finally, for long times and thick films, the rate becomes erratic, either increasing rapidly or leveling off. Below an oxygen pressure of 1 mm, the oxidation rate increases continuously with time, and the rate‐determining step in the kinetic process appears to be the dissociation of oxygen.