Protonic salts diffusion time

Figure 7. The variation of the rate of proton dissociation from excited hydroxypyrene trisulfonate on the molar concentration of the salt (O, ) time-resolved fluorescence measurements ( , ) steady-state fluorescence measurements (A) proton diffusion coefficient, normalized for pure water (data from Glietenberg et al. 1968). Open symbols, MgCl2 closed symbols, LiC104.

Activity in n-butane isomerization reaction of various alkaline salts of H3PW12O40 and H4SiWi2O40 was shown to be strongly dependent on the strength and number of accessible protons whereas the stability with time on stream was correlated to the presence of mesoporosity. For the liquid iC4/C4 continuous alkylation reaction, the strength and the number of acid sites appeared less important than the existence of mesoporosity indicating that the diffusion of the reactants and of the products plays an important role in this reaction. 

Cooke and Wien have found that the NMR proton chemical shift in muscle water is similar to that in an aqueous salt solution273. The relaxation times are different. But the activation energy of the diffusion co-efficient of cellular water in muscle... 

Fig. 8.2. Examples of ion exchange, monitored by FCS. (a) FITC measured at different pH. Decays of the correlation curves in the 1ms, 2-80 xs, and l xs time range are attributed to translational diffusion, proton exchange and single-triplet state transitions of the fluorophores, respectively, (b) FITC at pH6, with different concentrations of phosphate buffer. Inset Measured fcprot vs. concentration of buffer/salt at pH6. (c) FCS curves of GFP (S65T) at different pH. (d) The calcium sensitive dye Rh-II, measured at different concentrations of free calcium...

Local anesthetics are weak bases and are usually made as HCl salts which are soluble and stable in water. The pK of the compound determines when the ionized and unionized forms are equal (see Table 1 for values of pK and percentage ionization at pH 7.4). The time of onset of the block is related to diffusion of the anesthetic into the nerve fiber, which occurs only in the unionized, or non-proton-ated form. Sodium bicarbonate is often added (1 mEq(lOml) lidocaine or 0.1 mEq(lOml) ... 

EM base films cast from NMP solutions may exhibit changes in the intrinsic oxidation state when undergoing a protonation de-protonation cycle [85,86]. For protonation carried out in aqueous mineral acids, an acid treatment time of one hour followed by rapid deprotonation in NaOH, can increase the intrinsic oxidation state to that of NA. However, lower oxidation. states than that of NA were obtained from films with increasing acid exposure time. The increase in intrinsic state after one cycle of acid-base treatment is not readily observed in EM powders [85,86]. The difference in behaviour many be due to the hindrance to water diffusion and the associated hydrolysis reactions in the dense as-cast EM base films. PAN salt films obtained either by acid treatment of as-cast EM base film or by direct casting of PAN salts in NMP solutions also undergo a change in film morphology upon deprotonation [327]. As-cast EM base films lack porosity... 

SSNMR spectroscopy is unparalleled with respect to the diversity of techniques designed specifically to probe structure and dynamics with site selectivity, not to mention examine phase/component miscibility. Beyond the first-pass analysis of ID spectra to differentiate potential salt and co-crystal forms from those of the individual components, both relaxometry and 2D correlation spectroscopy have been increasingly used to characterize salts and co-crystals. H Ti (or Tih) relaxation time measurements can provide direct evidence of phase heterogeneity (to confirm the presence of phase impurities and/or rule out salt/ co-crystal formation) based on the observation of multiple relaxation times characteristic of different component phases in a given material. rip(or Tipn) relaxation, which like Tih relaxation, is strongly affected by efficient spin diffusion over the entire proton reservoir, is also frequently applied to study mixtures, and in favorable cases, both Tih and TipH measurements can allow domain sizes (hundreds of angstroms in the case of Tih) to be calculated. In contrast to relaxometry, which provides direct evidence of component phase separation, dipolar correlation techniques, for example, CP-HETCOR... 

The incorporation of tunicin whiskers induced an approximately threefold decrease in conductivity. Possible explanations include (i) the low dielectric constant of ceUulosic fillers, (ii) interactions between cellulose and PEO, and (iii) the effect of whiskers on salt dissociation and ion mobility. Indeed, the relaxation time of H protons was significantly reduced with the addition of whiskers, and the diffusion coefficients for both cation and anion decreased by almost a factor of 3." The decrease in ionic mobility is in... 

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