Kinetics of the Reduction of Lead Compounds and Glasses

The kinetics of the gas–solid reduction reactions of high purity dry hydrogen with selected lead compounds and glasses was investigated. Materials studied were PbO, Pb₂SiO₄, PbSiO₃, PbZrO₃, PbTiO₃, lead zirconate titanate (54/46, Zr/Ti ratio), lead orthosilicate glass, and lead metasilicate glass. A constant pressure (1 atm) hydrogen flow (2 liters per minute) system was used in reacting the powdered materials at specified constant temperatures. The extent of reduction was quantitatively determined by (1) weight loss of the reacted specimen, and (2) dew point of the reaction atmosphere. Expressions are presented for relating both the weight loss and the dew point to the fraction of reduction, a. The activation energies for the reduction reactions were calculated from plots of log h (reaction rate constant) versus 1/T °K. Activation energies obtained were 18.4, 19.9, 21.0, 34.6, 46.5, and 47.0 kcal per mole, respectively, for the first six compounds. The lead glasses, which reacted below their melting ranges, were reduced appreciably less than the lead compounds.