after each period of N2O etching, by measuring the mass loss rate in argon, in argon with N2O added, and again in argon. Rsublimation has Arrhenius temperature dependence, and was found to be significant compared to the N2O etching rates only for TNP ≥ 1800 K. Rbackground, attributed to etching reactions with background O2 and water (partial pressures ≤10 -7 Torr), was negligible compared to Rsublimation and RN2O except at the lowest TNP. The rates for etching by N2O or O2 ("RN2O", "RO2") have been corrected by subtracting Rbaseline from the raw mass loss rates measured with N2O or O2 added to the trap at known partial pressures (PN2O, PO2).