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Fast-flow apparatus

Brune et have described a new tandem axis laser magnetic resonance (LMR), resonance fluorescence, and resonance absorption fast-flow apparatus for the study of the kinetics of elementary gas reactions. They placed emphasis on the simultaneous time-resolved detection of reactants and products, crosscalibration of detection axes, the use of multiple sources of free radicals and computer simulation of the time-dependence of the reactant and product concentrations in experiments designed to determine elementary reaction rate constants. They provided data for the reactions N + OH — H+NO, N-1-H02— products, O+OH— -H+02, and 0 + H02- OH+O2. [Pg.125]

Fig. 7. Schematic diagram of a continuous fast-flow apparatus. (From Hester. )... Fig. 7. Schematic diagram of a continuous fast-flow apparatus. (From Hester. )...
The example above of tire stopped-flow apparatus demonstrates some of tire requirements important for all fonns of transient spectroscopy. These are tire ability to provide a perturbation (pump) to tire physicochemical system under study on a time scale tliat is as fast or faster tlian tire time evolution of tire process to be studied, the ability to synclironize application of tire pump and tire probe on tliis time scale and tire ability of tire detection system to time resolve tire changes of interest. [Pg.2950]

The main limitation of HEX reactors is the short residence time, typically from a few seconds to a few minutes. Indeed, the apparatuses are smaller than the traditional ones and fast flow velocities are necessary in order to maintain good level of heat-transfer coefficients. However, as described in the previous paragraph, the highlighted transfer properties of HEX reactors allow us to operate in a few minutes, whereas it takes many hours in batch or semibatch mode. [Pg.263]

The oxidation of Fe(II) by CI2 is fast ( 2 = 80 + 5 l.mole . sec at 25 X, fi = 3 M) and yields mostly FeCP on the several millisecond time-scale of a stopped-flow apparatus. This does not allow differentiation between one- and two-equivalent mechanisms. The analogous oxidation of hypochlorous acid, ki =... [Pg.466]

Figure 1. Fast-flow reaction apparatus. Ions or ion clusters are introduced into the flow tube from various sources and reactions proceed after they encounter the reactants added through a ring injector located at a selected position in the flow tube. The disappearance of the reactant ions and formation of products is monitored with the quadrupole mass spectrometer/electron multiplier shown. Taken with permission from ref. 19. Figure 1. Fast-flow reaction apparatus. Ions or ion clusters are introduced into the flow tube from various sources and reactions proceed after they encounter the reactants added through a ring injector located at a selected position in the flow tube. The disappearance of the reactant ions and formation of products is monitored with the quadrupole mass spectrometer/electron multiplier shown. Taken with permission from ref. 19.
It has long been known that substitution at the anion of Zeise s salt, [Pt(CH=CH2)Cl3], is, thanks to the high trans effect of the coordinated ethene, very fast. Recent developments in low-temperature stopped-flow apparatus have now permitted the study of the kinetics of substitution at Zeise s and other [Pt(alkene)Cl3] anions in methanol solution. These substitutions obey the customary two-term rate law (i.e. with kohs = ki+ /s3[nucleophile]), with large negative AS values for the k2 term as expected for Sn2 processes (196). [Pg.97]

When the preformed and isolated IRS - [14C]Ile-AMP is mixed with tRNA in the pulsed quenched-flow apparatus (Figure 7.4), the first-order rate constant for the transfer of the [14C]Ile to the tRNA is measured to be the same as the kcit for the steady state aminoacylation of the tRNA under the same reaction conditions. The rate constant for the reaction of the intermediate is thus fast enough to be on the reaction pathway furthermore, reaction of the intermediate appears to be the rate-determining step. [Pg.456]

Interfacial mass transfer of trace gases into aqueous pnase is investigated in a UV absorption-stop flow apparatus. For the first time, the mass accommodation coefficients are determined for O3 (5.3x10" ) and for SO2 (>2x10 2) The results are incorporated into a simple model considering the coupled interfacial mass transfer and aqueous chemistry in cloud drops. It is shown that dissolution of O3 into a drop is fast compared with its subsequent oxidation of dissolved S02 In addition, the conversion rate of S(IV) to S(VI) in aqueous drops by ozone reactions is not limited by interfacial resistance. [Pg.111]

Stopped flow and continuous flow methods [11] have been used to follow proton transfer reactions with half-lives in the millisecond range. The stopped flow method which is more popular is essentially a device for mixing the reactants rapidly (typically in one millisecond) together with some means of observing the fast reaction which follows. Proton transfer from p-nitrobenzyl cyanide to ethoxide ion in ethanol/ether mixtures at —77 °C was studied in this way [12]. The reaction was followed spectrophotometrically. The most rapid reaction occurred with ti/2 ca. 2 x 10 2 sec although the equipment was suitable for following reactions with f1/2 ca. 2 x 10 3 sec. A similar method has been used to measure rates of proton transfer between weak carbon acids (for example, triphenylmethane) and bases (for example, alkoxide ions) in dimethyl sulphoxide [13], A continuous flow apparatus with spectrophotometric detection was used [14] to measure rates of ionization for substituted azulenes in aqueous solution (4), reactions for which half-lives between 2 and 70 msec were observed. [Pg.100]

Lorimer and Pepper have recently reported a study of the polymerisation of styrene by perchloric acid in methylene chloride at low temperature. Althou the stop-flow apparatus they used was not very fast, some rough ideas on the kinetics of initiation could be obtained. Assuming that the initial increase in absorption at 340 nm was due to the protonation of styrene, unhampered by side reactions (esterification), the approximate rate law observed at —80 °C,... [Pg.48]

The complicated kinetic pattern obtained for the non-stationaiy phase of these polymerisations ccwld not be entirely mastered by Pepper and Lorimer. Unfortunately their stop-flow apparatus was not very fast and we feel that with a more modern version of this technique, such as the instmments used by other authors in the last few years more accurate and informative results could be gathered. However, tentative vdues of... [Pg.78]

A fast flow is used when filling a system, but once the reaction is set up, one bubble every 5-10s is adequate. A piece of apparatus which is very useful when used in conjunction with a double manifold is a Quickfit 3-way tap, which is also described in more detail in Chapter 4. [Pg.132]

Figure 5. Flow apparatus for measuring rates of fast reactions... Figure 5. Flow apparatus for measuring rates of fast reactions...
A comprehensive discussion is given by Tischmeyer. Only in the case when the reaction rate is slow is a fast determination of the phase equilibrium possible with a standard apparatus. In many other cases, special equipment must be used. A flow apparatus enables to resolve the reaction time as a reaction locus. So, an appropriate flow will make it possible to make the measurements. [Pg.35]

A more spectacular gaseous titration technique is used for the estimation of the concentrations of various atomic species. This involves the use of a fast flow discharge apparatus and the spectroscopic estimation of the extent of various chemiluminescent reactions. Hydrogen and nitrogen atoms may both be titrated with NO, and oxygen atoms with N02 or the reactions being... [Pg.78]

Carrington and Levy and Westenberg and de Haas have reviewed the early work on gas-phase reactions in this field. The apparatus involves a fast-flow system where a gas, at a relatively low pressure is passed through a microwave discharge to the resonance cavity of the spectrometer. At room temperature, it is possible to have the cavity in variable positions but at higher temperatures it is fixed °° (Figs. 62 and 63, respectively). The rate coefficients found for reactions (57)-(60)... [Pg.91]

Apparatus for filtration, Erlenmeyerflasks, Buchner flasks, funnel, fast flow filter paper, and water aspirator. [Pg.196]

Techniques for the study of alkali metal complex formation involve devices to measure fast reactions. There are only few exceptions, namely very stable cryptand complexes where the binding of metal ions might be elucidated using classical methods. Any of the recording instruments mentioned in Section 2.2 should be suitable to follow the kinetics of the reactions, possibly in combination with a flow apparatus. Processes with half times as low as 1 ms could easily be investigated in this way. (For technical detail cf.46- ). [Pg.135]


See other pages where Fast-flow apparatus is mentioned: [Pg.217]    [Pg.187]    [Pg.220]    [Pg.230]    [Pg.286]    [Pg.217]    [Pg.187]    [Pg.220]    [Pg.230]    [Pg.286]    [Pg.2948]    [Pg.634]    [Pg.509]    [Pg.179]    [Pg.136]    [Pg.287]    [Pg.659]    [Pg.902]    [Pg.509]    [Pg.280]    [Pg.554]    [Pg.158]    [Pg.65]    [Pg.6311]    [Pg.6321]    [Pg.6563]    [Pg.6563]    [Pg.174]    [Pg.123]    [Pg.345]    [Pg.613]    [Pg.300]    [Pg.203]    [Pg.738]    [Pg.14]    [Pg.201]   
See also in sourсe #XX -- [ Pg.472 ]




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