Kinetics of Reaction of SO2 with Marble

In industrial environments, the decay of marble takes place primarily due to atmospheric ${\mathrm{SO}}_2\text{.}$ In order to predict quantitatively the rate of weathering of marble, we reacted four varieties of marble at 20 °C and 100% relative humidity in atmospheres containing 10 and 300 ppm ${\mathrm{SO}}_2\text{.}$ The surface rate constant, $k_s$, was calculated from the mass loss of reacted samples upon leaching the reaction product by immersion in water. For application to marble, the grain theory model commonly used to evaluate gas‐solid non‐catalytic reactions was modified to provide for calculation of $k_s$ and the diffusion coefficient, $D_{\mathrm{eg}}\text{.}$ Further, the volumetric rate constant, $k_v\text{,}$ was determined based upon the x‐ray diffraction data. In both these cases, it was found that the total magnitude of reaction can be determined only through summation of the kinetically controlled initial reaction and the subsequent diffusion‐controlled reaction. The next paper in this issue uses these reaction constants to predict the weathering of marble in natural environments.