Oxygen dissolution experiments

In the paddle method, bulk Reynolds numbers range from Re = 2292 (25 rpm, 900 mL) up to Re = 31025 (200 rpm, 500 mL). In contrast, Reynolds numbers employing the basket apparatus range from Re = 231 to Re = 4541. These Reynolds numbers are derived from dissolution experiments in which oxygen was the solute [(10), Chapter 13.4.8] and illustrate that turbulent flow patterns may occur within the bulk medium, namely for flow close to the liquid surface of the dissolution medium. The numbers are valid provided that the whole liquid surface rotates. According to Levich (9), the onset of turbulent bulk flow under these conditions can then be assumed at Re 1500. 

Dissolved Oxygen. The experimental results demonstrate that in the absence of basalt, DO is maintained at high levels, while in the presence of basalt, oxygen is effectively removed (see Figure 1). Although the ferrous iron content of Umtanum basalt mesostasis is not well known, estimates from bulk ferrous/ferric iron data and from microcharacterization of mesostasis phases (7, 20) indicate that the amount of Fe2+ available for oxygen consumption by mesostasis dissolution is large relative to the amount of DO (>.10 on a mole/mole basis).Thus, the available Fe2+ concentration should remain constant over the duration of the experiments. 

The relationship of the stirring rate in these experiments to the rates of hydrolysis reactions of basalt phases is indicative of surface-reaction controlled dissolution (21). First order kinetics are not inconsistent with certain rate-determining surface processes (22). Approximate first order kinetics with respect to dissolved oxygen concentration have been reported for the oxidation of aqueous ferrous iron (23) and sulfide (24), and in oxygen consumption studies with roll-type uranium deposits(25). 

Activation control of an overall dissolution rate can, of course, reside in the reduction process, in the oxidation process, in a mixture of both, or in a mixture including some transport control. The reduction process is usually more influential in determining the overall rate. Thus, in the absence of transport control, the kinetics of the electrode process for reduction of hydrated protons, or water molecules, or dissolved molecular oxygen plays the major role in metal dissolution kinetics. Indeed the literature confirms the conclusion that many of the systems seen in experiment or in practice are diffusion controlled that most of the rest are under mixed diffusion and activation control and that those with some activation control... 

The CO2 method has also demonstrated the sensitivity of polyalkene photooxidation to the humidity of the oxygen environment. Previously, the effect of water has been attributed to factors such as dissolution and removal of reaction products by liquid water. This cannot be the case in the present experiments. 

V wilh respect to metal dissolution and - 0.8 V with respect to oxygen reduction. In most studies of electrode kinetics, however, the experiment is set up in such a manner that only one reaction can take place in the range of potential studied, and the overpotential is unambiguously defined. 

The study of the kinetics of oxidation (photochemical oxidation in particular) of aldehydes in liquid phase by dissolved oxygen has generally been carried out by measuring, as a function of time, the volume of oxygen absorbed at constant pressure. In experiments of this kind, the rate of dissolution of oxygen is governed by the chemical phenomenon and not by a physical phenomenon of diffusion, provided the two following conditions are fulfilled simultaneously (cf. references 5a and 5b) ... 

The study was made at much lower temperatures (—90 to —40°C.), to avoid any bad effects on the dissolution of O2 caused by the high vapor pressure manifested by ethanal at room temperature. This also lowered the rate of thermal oxidation to a value which was negligible compared with that of the photochemical reaction. Since ethanal was at that time very difficult to dissolve in the usual solvents, all the experiments were carried out on the pure substance. The liquid was irradiated with ultraviolet light with an average wavelength near 3000 A. (mercury lines 2967, 3023, and 3130 A.) the oxygen pressure varied between 0.2 and 1 atm. 

The majority of studies on surface chemistry of ion-bombarded samples are concerned with the oxidation arid corrosion of materials. One part of the experiments covers the corrosion and oxidation in gaseous atmosphere such as air or oxygen at normal or high temperatures. The other, smaller, part deals with aqueous corrosion, in particular with the dissolution of metals and the formation of passivating layers in aqueous solutions. The interest in this subject found its expression in two conferences in 1975 and in 1978 ... 

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