Varying Oxygen Partial Pressure Research Articles

Oxygen Transport and Reaction Rates at an Air‐Depolarized Copper Cathode

Air‐depolarized partially submerged electrodes were studied to determine the location of the zones of reaction and the rate‐controlling steps in their operation. Reaction was found to occur primarily on that part of the surface of the electrodes covered by the electrolyte meniscus. The rate‐controlling step was the diffusion of oxygen through the liquid meniscus to the electrode surface. The mass transport of oxygen as a rate‐controlling step was eliminated in a specially constructed wiped, rotating, partially submerged copper electrode. This electrode was used to measure the oxidation rate of copper at room temperature for various partial pressures of oxygen. Oxidation rates were found to be great enough to support far larger current densities than are generally attainable in normal oxygen‐electrode operation. The oxidation of copper was found to follow the logarithmic equation where was independent of oxygen partial pressure, and was proportional to the square root of the oxygen partial pressure.

Automatic control of dissolved oxygen levels in fermentations

AbstractDissolved oxygen levels in fermentation systems are affected by (a) gas flow rate, (b) degree of agitation, and (c) oxygen partial pressure in the gas. Since the first two variables cannot easily be separated, a method for dissolved oxygen control has been devised based on the variation of oxygen partial pressure in the gas. Oxygen and nitrogen are fed to a special mixing valve capable of varying the proportions of the two gases while keeping the total flow rate constant. A dissolved oxygen electrode and control system adjust the valve setting to automatically maintain a preset oxygen level. Oxygen analyzers, monitoring the inlet and outlet gas streams, provide additional information from which oxygen absorption and uptake rates may be determined. The system provides a means for the quantitative and independent study of aeration and agitation effects. In addition, it offers a basis for routine control of oxygen levels in plant fermentation equipment.

The effect of oxygen on the radiosensitivity of growing bone in the tail of the mouse.

The effect of X irradiation on the growth of the tails of young mice was investigated. The animals were irradiated when seven days old, and the growth during subsequent weeks was compared with that of litter-mate control animals. The reduction in growth was found to give a reproducible index of radiation damage. The tails of groups of animals were irradiated while breathing various partial pressures of oxygen ranging from one-tenth to three atmospheres. The tails of another group were irradiated with the blood occluded to render them anoxic. In this way the variation of relative radiosensitivity of the growing mouse tail was determined for various partial pressures of oxygen in the respired gas.

The routine-active oxygen consumption of the milk fish

Seasonal variations in temperature, dissolved oxygen and salinity have great influence upon marine life. However, these factors incidental to the tropical environment have not been fully investigated. In this paper some effects of a sudden change in temperature as well as the effects of various partial pressures of oxygen upon its uptake are presented with reference to Chanos chanos-the milk fish, so widely used in fish culture. An attempt has also been made to relate this study to a limited range of size of the fish.