GASEOUS REDUCTION RATES OF SOLID SILICA.

Spherical specimens of solid transparent silica were suspended in a stream of hydrogen or carbon monoxide. Reduction rates ranged from 0. 7 multiplied by 10**-**7 to 4. 5 multiplied by 10**-**7 mol/cm**2 sec for H//2 reduction and from 3. 0 multiplied by 10**-**9 to 2. 4 multiplied by 10**-**8 mol/cm**2 sec for CO reduction. The specific reduction rates increased with increase of gas velocity and temperature but decreased with increase of sample diameter. The results are interpreted to show that the rate of reduction of silica in hydrogen is controlled by mass transfer in a gas film. In carbon monoxide, there is mixed control by mass transfer and interfacial reaction.