Kinetic investigation of the reaction between tungsten and bromine

Abstract

The reaction between tungsten and bromine has been studied between 1 063 and 1 213 K with bromine concentratrations of 0·5–1·5 mol m^–3 in a static system utilising a quartz spring to record weight loss. The reaction is zero order with respect to tungsten concentration, but the order with respect to bromine varies from 1·70 to 1·16 with increase in temperature. The species produced at the tungsten surface are probably WBr₂ and WBr₅ and their formation is attributed to stepwise attack by atomic bromine on the tungsten. The rate constant over the temperature range is given by k/mol^–½m^5//₂s^–1= 1·12 × 10^–9 exp –(82·7 ± 4·0 kJ mol^–1/RT). The effect of addition of argon and nitrogen on the reaction system has been studied. Reaction rates are in excess of those expected for simple dilution and this is partially explained on the basis that the increased rate is a consequence of traces of oxygen present in the two gases.