THE EFFECT OF DOPING ON THE THERMAL-DECOMPOSITION OF SODIUM-BROMATE

The thermal decomposition of sodium bromate doped with potassium bromate and sodium bromide, each in the mole fraction range 10(-4)-10(-1), was studied by thermogravimetry. The activation energy, frequency factor and entropy of activation were computed using the Coats-Redfern, Freeman-Carroll and Horowitz-Metzger methods. Doping enhances the decomposition and decreases the energy of activation, the effect increasing with increase in concentration of the dopant. The mechanism of decomposition follows the Avrami equation, 1 - (1 - alpha)1/3 = kt, and the rate-controlling process is a phase-boundary reaction assuming spherical symmetry.