Law Plots Research Articles

Kinetics of the Oxidation of Pure Tungsten from 500° to 1300°C

Kinetic studies were made on the oxidation of tungsten from 500° to 1300°C for time periods up to 6 hr, and for oxygen pressures from 0.1 atm to 0.00132 atm. The rate data were fitted to the parabolic rate law. A number of deviations and transitions were observed. For all of the experiments the initial slopes of the parabolic rate law plots were smaller than the final values found for thick films. A transition in the rate of oxidation was observed for weight gains of 2500–4000 µg/cm2 at temperatures of 650°–800°C. Photographs of the oxidized surface above 650°C show that oxidation occurs in a preferential manner at the edges. Pressure had a strong effect on the rate of oxidation for the experiments above 950°C. At 1200°C weight loss curves were observed for pressures as high as 0.1 atm. Above 1200°C the oxidation reaction is similar to the combustion of graphite. The rate of oxidation is limited by the volatility of , the diffusion of oxygen to the surface, and the diffusion of away from the surface.

High Temperature Oxidation of High Purity Nickel between 750° and 1050°C

Kinetic studies on the oxidation of nickel using the vacuum microbalance method have been extended to 1050°C in order to determine the conditions and mechanisms of breakdown of the metal in oxidation. Below 900°C Ni oxidizes in the normal manner and the rate data fit in well with experimental rate relationship already established. At 900°C and higher, parabolic rate law plots of the data show increasing values of the constant with time. At 1000°C and higher, the oxide cracks away from the metal. It is suggested that Ni fails in protective oxidation due to a loss of adhesion at the oxide metal interface.

Rectification of Nonlinear Beer's Law Plots

Rectification of Nonlinear Beer's Law Plots

Transmittancy of commercial sugar liquors: dependence on concentration of total solids

The dependence of the transmittancy of a commercial sugar liquor on the concentration of total solids does not in general follow Beer's law. This behavior is attributed to the presence of appreciable light-scattering material in the solution. A linear dependence has been found to relate the concentration with the reciprocal of a*, the latter being; defined as equal to (—log T8)/bc, where T8 is the transmittancy, b the cell length, and c the concentration of total solids. The intercept at c=0 in a plot of I/a* versus c is equal in magnitude to the limiting slope of the Beer's law plot.