Bases titration data

A. Kraft, Determination of the pAfa of Multiprotic, Weak Acids by Analyzing Potentiometric Acid-Base Titration Data with Difference Plots, ... 

Recent studies have shown that the NICA-Donnan model fits very well to the acid-base titration data of HAs and FAs form organic amendments and of unamended and amended soils, pointing out substantial differences in site densities,... 

Accurate measurement of surface acidity constants for reactions 11 and 12 can be difficult (Davis and Kent, 1990 Dzombak and Morel, 1990), especially for natural systems (Stollenwerk, 1995). Acidity constants are often derived from acid-base titration data (Parks and de Bruyn, 1962), and constants for several metal oxides have been published. These published values have been used as initial estimates for modeling adsorption in natural systems with complex mineralogy. The acidity constants have then been optimized simultaneously with equilibrium constants for other solutes to give the best fit to experimental data (Goldberg and Glaubig, 1988b Kent et al, 1995 Kent et al., 2001). 

From the analysis of the acid-base titration data in Figures 5.30 through 5.34, positive cooperativity results from the apolar-polar repulsive free energy of hydration, that is, from the competition for hydration between apolar (hydrophobic) and polar (e.g., charged) species. The general statement can be that the appearance on the scene of the first polar, for example, charged, species must do the work of destructuring hydrophobic hydration in order to achieve adequate hydration for itself. 

Figure 5. Two-phase potentiometric acid-base titration data for PSl6o in n-octanol Na" " (x), K" " (o), Cs" " (A) in the presence of 10 2 M NaCl, KCl, CsCl (aqueous phase).

The acid-base titration data exhibit unusual characteristics compared to the classic curves usually... 

Table 1 Material feature and interfacial acid-base processes assumed in the surface com-plexation model for montmor-illonite, and the results of fitting potentiometric acid-base titration data at different ionic strengths.

Figure 19.7 Curve for a strong acid-strong base titration. Data (af/eft) for the titration of 40.00 mL of 0.1000 M HCI with 0.1000 M NaOH. In a strong acid-strong base titration, pH = 7.00 at the equivalence point. Each molecular view shows the relative numbers of species, other than solvent (any H2O shown is the product of the reaction), at one point during the titration.

In both models, the concentration of surface species was calculated from acid-base titration data to determine the speciation of the solution-solid interface. From a knowledge of the concentration of solution and interfacial species, the mass action... 

Wyman and collaborators presented conclusive experimental evidence that Conant s assumption was justified—that imidazole residues of histidine must be linked to the iron in hemoglobin. The differential acid-base titration data of German and Wyman (30) between hemoglobin and oxyhemoglobin were taken as the base for calculations by Wyman (92), and these established the existence in hemoglobin of two acid groups (pK 5.25 and 7.81). On oxygenation, these values shifted to 5.75 and 6.80. 

Fig. 9. Genesis of acid tain (13). From the oxidation of C, S, and N during the combustion of fossil fuels, there is a buildup in the atmosphere (gas phase, aerosol particles, raindrops, snowflakes, and fog) of CO2 and the oxides of S and N, which leads to acid—base interaction. The importance of absorption of gases into the various phases of gas, aerosol, and atmospheric water depends on a number of factors. The genesis of acid rain is shown on the upper right as an acid—base titration. The data given are representative of the environment in the vicinity of Zurich, Switzedand.

This method is applicable when the fluorescence of a ligand is quenched in presence of DNA or RNA and provides base-dependent specificity [135]. In fluorescence quenching experiments the titration data is plotted according to the Stern-Volmer equation ... 

Avdeef, A. Weighting sdieme for regression analysis using pH data from add-base titrations. Anal. Chim. Acta 1983, 148, 237-244. 

The authors studied, as they call it, "acid-base equilibria in glacial acetic acid however, as they worked at various ratios of indicator-base concentration to HX or B concentration, we are in fact concerned with titration data. In this connection one should realize also that in solvents with low e the apparent strength of a Bronsted acid varies with the reference base used, and vice versa. Nevertheless, in HOAc the ionization constant predominates to such an extent that overall the picture of ionization vs. dissociation remains similar irrespective of the choice of reference see the data for I and B (Py) already given, and also those for HX, which the authors obtained at 25° C with I = p-naphthol-benzein (PNB) and /f B < 0.0042, i.e., for hydrochloric acid K C1 = 1.3 102, jjrfflci 3 9. IQ-6 an jjHC1 2.8 10 9 and for p-toluenesulphonic acid Kfm° = 3 7.102( K ms 4 0.10-6) Kmt = 7 3.10-9... 

Table II shows the "heats of formation" of the conjugate phases, that is, the excess enthalpies for mixing the appropriate amounts of water and amphiphile (at the same initial temperature and pressure as the final system) to make a unit amount of the conjugate phase. Values labeled "calorimeter" and "phase volume," respectively, are based on the same set of calorimetric titrations. In the former case the phase composition was taken from the calorimetric measurements, and in the latter case the composition was taken from our phase-volume compositions. Literature values for the heats of formation are based on data from references 13-16.

Based on your titration data and calculations for determination 1 ... 

This experiment is an acid-base titration similar to those performed in Chapters 4 and 5. It is the titration of 0.10 M HC1 with 0.10 M NaOH, as in Experiment 8, but a combination pH probe will be used to monitor the pH during the titration, as in Experiment 10. The pH meter to be used has an RS232 output to interface with a microcomputer. We will use this special feature of the pH meter to feed the pH data directly to a microcomputer in an example of data acquisition by computer, and observe the titration curve traced on the screen in real time. 

Returning to our introductory remarks about the existence of various models for the oxide/solution interface, It may be appropriate to point out that the results of very relevant experiments based on electrokinetic measurements are often not used in conjunction with titration data. Granted that there may be additional difficulties in identifying the precise location the slipping plane and hence the significance of the electrokinetic c potential may be open to debate, both titration and electrokinetic data ought to be combined where possible to elucidate the behaviour of the oxide/solution Interface. 

Recently a new pH-stat instrument (PHM290 with autoburet ABU901) was introduced by Radiometer International A/S. This instrument can be connected directly to a personal computer, so that titration data and pH can be recorded in a Windows-based program. A recording of corrosion potential must then be made by another instrument, but both titration data and potential measurements can be recorded simultaneously using two inputs. 

Fig. n.6 Ca titration of 15 aM porcine CaM in three different media (99% D2O) [25]. Line(a) 50 mM HEPES/0.1 M KCI, apparent pH 7.4. Line (b) 50 mM HEPES, apparent pH 7.4. Line (c) 2 mM NH4OAC, apparent pH 7.0. Error bars were based on two sets of LCQ titration data. Solid curves were taken from the four-parameter model and are the best fit for the average data. 

Perrone et al. (2001) modelled Ni(II) adsorp-tion to synthetic carbonate fluoroapatite (CaI0 ((P04)5(C03))(0H,F). The solid phase had a pHIEP of 6.3 and a ZPC of 6.4 with an SSA of 8.8m2/g, an estimated sorption site density of 3.1 sites/nm2. They conducted 8-day isotherms in closed vessels at Ni concentrations of 5 x 10-10 to 1 x 10 8 M, constant I (0.05, 0.1 or 0.5 M), constant solid phase concentrations of 10 g/dm3 at pH values of 4 to 12. As Ni sorption occurred, no significant release of Ca was seen. Sorption was reversible. Rather than precisely characterize surface functional groups, they elected to describe their sorbent surfaces using acid-base reactions for the average behaviour of all sites involved in protonation and deprotonation. Potentiametric titration data were used to estimate the constants with the FTTEQL computer code ... 

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