Pressure jump experiments

Quednau J and Schneider G M 1989 A new high-pressure cell for differential pressure-jump experiments using optical detection Rev. Sc/. Instnim. 60 3685-7... 

Temperature jump studies were performed in combination with stopped-flow experiments94 in response to criticism as to the reliability of temperature jump experiments26,142 and divergent interpretation of the kinetics. In particular, the suggestion from pressure jump experiments that the association step is diffusive in nature... 

Table 8 Equilibrium constants and association and dissociation rate constants for derivatives 27 and 28 with a-CD determined by temperature jump (27, T — 14 °C, I — 0.5 M), stopped-flow (28, T = 25 °C, /= 0.1 M) and with pressure jump experiments (29, T = 25 °C, /= 0.15 M)...

The circles refer to the pressure jump experiments of Hachiya et al. The relationship is expressed by an almost linear correlation (slope 0.92) ... 

Linear-free energy relation between the rate constants for water exchange k w [s 1] and the intrinsic adsorption rate constants katjS(int) [M 1 s 1] from the pressure jump experiments of Hachiya et al. The intrinsic constants refer to an uncharged surface. The linear-free energy relations based on the experimental points are extended to some ions with lower H20 exchange rate in order to predict adsorption rates. 

The simplest experiment we can visualise performing is the very rapid application of a small strain which is then maintained at a constant level. This is simply a strain-jump experiment and can be treated in an analogous fashion to a temperature or a pressure-jump experiment. The stress will follow the strain and increase to a maximum value. For an... 

Figure 4.4. Typical oscillograms of pressure-jump experiments. Relative change in conductivity for pressure-jumps of 13.1 MPa in solutions of 0.05 M InCI, pH = 3.25. (a) At 383 K showing only pressure decay, (b) At 300.5 K, r = 50 15 /us. (c) At 273.7 K. r = 215 10 jj.s. (d) Solution of 0.10 M a-ketoglutaric acid, pH 1.69. at 274 K, t = 25.8 s. [From Knoche and Wiese (1974), with permission. ...

First, we present pressure jump experiments carried out in DEPC-water dispersions to study the Lp-L gel-to-fluid main transition, which occurs at Fm = 12 °C at ambient pressure and which has a pressure dependence of ATJAp = 20 °C kbar . Selected SAXS diffraction patterns at 18 °C after a pressure jump from 200 bar (L phase) to 370 bar (Lp phase) are depicted in Fig,... 

Clearly both the electrostatic interaction 2 nd the line tension between gel and fluid phases " have been shown to dramatically affect size and morphological shapes of the domains formed. In the extreme case, arising from diffusion limited aggregation effects, even dendritic growth on pressure-jump experiments has been reported.25... 

Adsorption kinetics will be discussed first. Figure 11A shows the equilibration of the alumina system after the addition of HCl [16]. Figure IIB shows that the adsorption of Cu, with liberation of protons [47], takes about 24 h to reach equilibrium. Figure 11C gives kinetic data for the adsorption of Co, Fe, and Ni ions [54], evidently in equilibrium after about 1 h. On the other hand, pressure jump experiments of Cu adsorption used a time scale of 10 -10 s [55]. These results are mentioned to demonstrate that reactions taking place in the adsorption system may have rates that differ by several orders of magnitude. 

Hachiya et al. [60,61] found a linear relationship between the logarithms of intrinsic adsorption constants and the hydrolysis constant of the metal ions for Cu, Pb, Zn, Co. and Mn. They described pressure jump experiments [61] with y AI2O3, showing a fast and a slow process — attributed to two surfaces sites — with Cu ", Zn, Co, and The relaxation times decreased with metal ion... 

The kinetics of intercalation and deintercalation of alkali metal ions were investigated in pressure-jump experiments while monitoring the electrical conductivity of the samples (32). These studies indicate biphasic kinetics whose magnitudes are in milliseconds the rates of the fast and slow components increased with increased concentrations of the metal ions. The forward and reverse rates depend on the interlayer distances, and the fast and slow components have been attributed to the ingress of ions into the galleries and interlayer diffusion, respectively. Similar biphasic kinetics on millisecond-second time scales were also observed in pressure-jump experiments for the deprotonation-reprotonation of a-ZrP (33). In the latter case, the slow and fast components have been attributed to deprotonation from the surface and from the interlayer regions of the solid, respectively. 

Shift of equilibrium concentration y and actual concentration y at a pressure jump experiment, t in arbitrary units, y is calculated for a single rslaxation effect with T = 1 and pressure drop at... 

As the process free ions —Pouter sphere complex is fast, the reaction in pressure-jump experiments is characterised by a single relaxation time. 

Ultrasonics Ultrasonics works on the same principle as the pressure jump experiment in that pressure is changed. The system to be studied is irradiated with an ultrasonic transducer which causes a repeating pressure fluctuation(Stuehr 1986). If the period of the ultrasonics is much longer than the time of the chemical reaction being studied, the chemical system will shift as the equilibrium constant shifts and there will be no absorption of energy. If however the reaction that is being studied occurs on the same time scale as the pressure... 

T. Emilsson, M. Grubele and H. Bohr, Proposal for a pressure jump experiment, Carlsberg Funding, 1996... 

We have discussed temperature-jump experiments. Pressure-jump experiments are analyzed in the same way, with sudden changes in pressure that produce partial pressures that deviate from equilibrium partial pressures at the new total pressure. 

---