Inert-atmosphere experiments

Typical arrangement of apparatus for an inert-atmosphere experiment. Note that the surrounding bath may be used to heat (oil bath) or cool (ice bath) a reaction. When heating, a reflux condenser would be placed in one of the necks of the reaction flask. 

A different picture was obtained in the case of the reference Pt—BaAy-A Oj (1/20/100 w/w) sample (Figure 6.12). In the case of the TPD experiment performed after NO, adsorption at 350°C, the decomposition of stored NO, species was observed only above 350°C. Evolution of NO and 02 was observed in this case, along with minor quantities of N02 [25,28,33,35], Complete desorption of NO, was attained already slightly below 600°C. As in the case of the binary Ba/y-Al203 sample, the data hence indicate that nitrates formed upon N0/02 adsorption at 350°C followed by He purge at the same temperature, did not appreciably decompose below the adsorption temperature during the TPD run under inert atmosphere. 

In principle, the analysis of molecules, ions and adsorbed intermediates is possible if they survive the emersion (no potential control) and UH V conditions (elimination of most of the solvent). The use of ex situ methods for the analysis of sub-monolayer quantities of oxygen-sensitive substances requires an extremely inert atmosphere when the electrode is emersed. In order to check whether a given adsorbate survives the experimental conditions, a control experiment must be carried out, as we describe here for adsorbed CO on Pt. 

The study of metal ion/metal(s) interfaces has been limited because of the excessive adsorption of the reactants and impurities at the electrode surface and due to the inseparability of the faradaic and nonfaradaic impedances. For obtaining reproducible results with solid electrodes, the important factors to be considered are the fabrication, the smoothness of the surface (by polishing), and the pretreatment of the electrodes, the treatment of the solution with activated charcoal, the use of an inert atmosphere, and the constancy of the equilibrium potential for the duration of the experiment. It is appropriate to deal with some of these details from a practical point of view. 

Mechanism [5] was based on the results obtained from multi-step sequential pyrolysis experiments in an inert atmosphere (23). This mechanism [5] differs from [3], primarily in that [5] was proposed to be surface catalytic in nature, and that the reaction between the oxide particle surface and the organohalogen was considered only as the first step, initiating the process leading to the eventual formation of volatile antimony species. 

Some of the procedures described in the following chapters had to be carried out under an inert atmosphere, nitrogen or argon, to minimize contact with oxygen and moisture. It is then necessary to use Schlenk techniques including the utilization of a vacuum line connected to a high vacuum pump and an inert gas inlet. The use of such equipment requires experience in working under anhydrous conditions. 

This method, specific for the epoxidation of allylic alcohols, gives good results if the reaction is carried out under strictly anhydrous conditions, otherwise the yield or the enantiomeric excess can decrease, sometimes dramatically. This can explain the small differences between the results obtained during the validation experiments and the published results. All the different reagents are commercially available they can be used as received but in case of low yield and/or enantiomeric excess they should be distilled and dried under an inert atmosphere. Table 5.1 gives some other examples of substrates which can be epoxidized using the procedure described above. 

Repeated visual examination and impedence measurements indicated no degradation of the electrode over the course of the experiments (3 weeks). During this time, the selected electrodes were stored in the inert-atmosphere glove box in which the electrochemical experiments were performed. No electrode pretreatment procedures were used and the crystals were not recleaved. 

The photoacoustic calorimeter of figure 13.6 can be divided into three subsets of instruments converging on the sample cell. The first set is used to initiate the photophysical process in the cell the second allows the detection and measurement of the photoacoustic signal produced the third is used to measure the solution transmittance. A flow line conducts the solution throughout the system. The calorimeter can operate under inert atmosphere conditions, and the temperature variation during an experiment is less than 0.5 K. 

Intramolecular Electron-Transfer Rates. Experiments were carried out under inert atmosphere by reducing a known concen-... 

In order to produce an aqueous solution which fulfills these criteria, 120 g each of basalt, quartz monzonite, and shale were ground to powders less than 37 m in diameter. Each of the samples was placed in two liters of distilled-deionized water which had been pre-equilibrated with an atmosphere containing 10 percent CO2, 90 percent Ar, and 10 ppm Og. The experiment was carried out in an inert atmosphere box at room temperature (26 + 2°C). Samples of the fluid (10 ml) were extracted at various times over a 35-day period and filtered (O.OSpm). Analyses for Na, K, Mg, Ca, Fe, Al, Si02 (aq). Eh, and pH were made on each sample. The experiment was terminated at the end of 846 hours and analyses for HCO3, SO4, and Cl were made on each of the fluids. 

ProcedureSe One of the rock wafers from each of the containers used in the adsorption experiments was placed in a new polyethylene bottle containing 50 ml of the appropriate aqueous solution. The containers were removed from the inert atmosphere box and gently agitated for six weeks. Tracer concentrations in the solution were measured periodically as described previously. At the end of six weeks, the experiments were terminated, the wafers removed from the containers, and the tracer concentrations of the components of the system determined in the same manner as in the adsorption experiments. 

Comparable or larger errors are introduced by unwanted convective mass transport. Convection is caused by physical motion of the solution, sometimes purposefully introduced for techniques such as rotating electrode voltammetry. When a quiet solution is desired, however, convective errors may arise at longer experiment times (slow scan rates) from mechanical vibrations of the solution. Convection is a particular problem for cells inside inert-atmosphere boxes, on which fans and vacuum pumps may be operative. Convection raises the current... 

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