Charles H. Pitt

The kinetics of gold cyanide adsorption on activated charcoal

Adsorption rates of gold cyanide on activated carbon were determined as a function of temperature, free cyanide concentration and charcoal concentration. The experimental rate data is explained by use of a diffusion controlled model developed by Crank. The adsorption rates were determined to be controlled by pore diffusion with the effective diffusion coefficient having an activation energy of 3.3 kcal/mol. Good agreement between experimental rate data and predicted rate curves by the diffusion model was obtained.

Dislocation Velocities in Nickel Single Crystals

The velocities of dislocations moving in nickel single crystals were measured at various temperatures as a function of stress. The data were found to fit an equation obtained from reaction‐rate theory.The activated volume varied approximately linearly with temperature and was independent of the applied stress over the rather limited range of stresses investigated.The enthalpy of activation was also independent of stress but changed abruptly with temperature from 1200 cal/mole at approximately 130°K to 2500 cal/mole at higher temperatures. This change is explained by a change in the Peierls stress, which is associated with a sudden increase in dislocation density at higher temperatures. The dislocations were believed to be emitted from sources which are thermally activated.

The adsorption of silver cyanide on activated charcoal

Experiments have been carried out on the adsorption of silver cyanide on charcoal from solution having various concentrations of sodium, calcium, free cyanide, and hydrogen ion. It has been found that sodium and calcium ions enhance the adsorption of silver cyanide on charcoal while free cyanide ions reduce the adsorption. A qualitative description of the adsorption based on the structure of the electrical double layer has been proposed to explain the effect of sodium, calcium and free cyanide ions on the adsorption. Increasing acidity of solution enhances the adsorption of silver cyanide on charcoal except in a certain pH range. The adsorption of silver cyanide in acid solution seems to be influenced by the zeta potential of the charcoal particles rather than by the adsorption of hydrogen ions. The adsorbability of different size ions on charcoal has been determined. The larger ions have a greater adsorption potential as shown by the order of adsorption amount with gold cyanide > silver cyanide > cyanide.

Kinetics and thermodynamics of silver cyanide adsorption on activated charcoal

An investigation has been carried out on the adsorption of silver cyanide from solution onto activated charcoal. The isosteric heats of adsorption and equilibrium constants for adsorption were determined from adsorption isotherms. The isosteric heat and equilibrium adsorption constants were shown to decrease with increasing surface coverage at low surface coverages while at intermediate surface coverages they remain fairly constant. The experimental isotherm data was found to fit the Langmuir adsorption isotherm in this intermediate range of surface coverage. A pore diffusion model was utilized to explain the experimental rate data. The experimental rates were found to be controlled by pore diffusion with the effective diffusivity having an activation energy of 2.6 kcal/mol. Good agreement between experimental rate data and predicted rate curve by the diffusion model was obtained.

Physical behaviour of oil shale at various temperatures and compressive loads: 1. Free thermal expansion

Abstract The effects of grade and specimen orientation on the free thermal expansion of oil shale were investigated. The expansion was found to increase with the grade of the specimen and to be dependent on orientation. The change in heating rate from 1.0 K min −1 to 3.5 K min −1 had little effect on the expansion of oil shale. It was found that many of the oil shale specimens would settle under their own weight once kerogen left the oil shale. The thermal expansion coefficients in the temperature range 373–473 K were determined to be little affected by increases in grade. A polynomial correlation of expansion versus grade and temperature in the temperature range 298–698 K is presented. The behaviour at temperature up to 1000–4000 K was also investigated.

Current Energy Requirements in the Copper Producing Industries

An analysis of energy usage in the production of refined cathode copper was made from mining ore to cathode copper. In mining copper ore the greatest energy consumers are ore hauling and blasting. Another important factor is the “recovery efficiency” of the metallurgical processes used to extract the copper. The mining and mineral concentrating energies are directly proportional to the “recovery efficiency,” with a typical mining operation requiring about 20 million Btu/ton of cathode copper produced. Mineral concentrating was also found to be a large energy consumer, requiring about 43 million Btu/ton of cathode copper. Some possibilities for energy savings in the mineral processing area include use of autogenous grinding and computer control for optimizing grinding operations, improved classifier efficiency, and optimizing the entire concentrator plant performance by interrelating all plant operations.

Stress Relaxation in Nickel Single Crystals between 77°−350°K

Stress‐relaxation tests were conducted in compression with nickel single crystals of various orientations and purities. The experiments were performed at five temperatures, 77°, 153°, 198°, 298°, and 350°K. The data are fit by the semilogarithmic equation, Δτ(kT/B) (In A′t+1), based on reaction rate theory. Crystals oriented to produce glide on intersecting slip planes exhibited no relaxation at the three lower test temperatures. This absence of relaxation is believed to be a result of the high activation enthalpy necessary to produce dislocation motion across the intersecting glide dislocations which would markedly reduce the rate of thermal activation. Crystals oriented to produce slip on a single set of planes had only one relaxation curve at low temperatures; no subsequent relaxation after the initial one could be induced. At higher temperatures, after relaxation had ended, new relaxation was easily initiated by increasing the stress slightly. The activated volumes obtained were almost independent of ...

Physical behaviour of oil shale at various temperatures and compressive loads. 2. Thermal expansion under various loads

Abstract The thermal expansion of oil shale for various applied compressive loads, grades and orientations of the bedding plane to the applied load have been measured. It was determined that increasing the compressive load decreases the maximum expansion. Under loads

Physical behaviour of oil shale at various temperatures and compressive loads: 3. Structural failure under loads

Abstract Most of the medium- and high-grade specimens of oil shale structurally failed during heating under a load above 0.1–0.5 MPa in the temperature range 650–770 K, while the low-grade specimens did not fail up to a load of 4.83 MPa. Increasing the compressive load decreased the temperature at which structural failure occurs. The load above which failure occurred was lower for higher-grade samples.

The recrystallization of 99.997% chromium

Abstract Recrystallization data were obtained on samples of warm worked 99.997% chromium that had been deformed 60% by rolling. The per-cent recrystallized as a function of time was obtained using quantitative optical microscopy techniques. Specimens in various stages of recrystallization yielded activation energies of about 80 kcal/mole. The recrystallization data were analyzed using the theory of Avrami. Deviations from the theoretical equations occurred in the initial part and latter stages of the recrystallization process. The initial deviation was attributed to the overlap of recovery with recrystallization, which was confirmed by transmission electron-microscopy studies, while the latter deviation was attributed to the lack of perfectly random nucleation. Isothermal grain-growth measurements were conducted on the growing, unimpinged, recrystallized grains. An initial decrease in the growth rates was attributed to a decrease in the strain energy by concurrent recovery and recrystallization processes occurring during the initial stages of recrystallization. When the recovery processes were essentially complete, the growth rates became constant until extensive impingement of the grains began to occur.