Potentiometric titration characteristics

The study of these electrodes has proved primary and secondary characteristics favorable to their practical utilization in potentiometric titrations and in direct potentiometric determinations. 

Table 12 the characteristics of the papers dealing with edl at the oxide-electrolyte solutions interface were presented. There are some that have considerable solubility (CdO and ZnO). These oxides are sensitive to the CO2 adsorption but also eagerly form the hydroxy salts type compounds [73,255]. The latter may form also during the potentiometric titrations because of the sediment dissolution. 

Hydrous sodium titanate was prepared by the method of Dosch and Stephens (1). Titanium isopropoxide was slowly added to a 15 wt% solution of sodium hydroxide in methanol. The resulting solution was hydrolyzed by addition to 10 vol% water in acetone. The hydrolysis product is an amorphous hydrous oxide with a Na Ti ratio of 0.5 which contains, after vacuum drying at room temperature, approximately 13.5 wt% water and 2.5 wt% residual alcohol. The ion-exchange characteristics of the sodium titanate and the hydrolysis behavior of the nickel nitrate solutions were characterized using a combination of potentiometric titrations, inductively coupled plasma atomic emission (ICP) analysis of filtrates, and surface charge measurements obtained using a Matec electrosonic amplitude device. 

The characteristic properties of some soils, studied by potentiometric titration and the surface complexation model, are shown in Table 3.12. The mineral composition of some soils are also provided (Table 3.13). 

Acoustic spectroscopy has several characteristics that make it useful. One clear advantage over light-scattering techniques is the ability to stir, pump, or otherwise physically agitate the sample during analysis, making the technique well suited to potentiometric titration and analysis of unstable suspensions. When the acoustic signal is measured as a function of the transmitter-receiver gap, it requires no... 

Polymer-polymer complexation is generally detected via conductometric or potentiometric titrations. Colloid titration represents an inverse-system where a polymer with known characteristics, such as potassium poly (vinylalcohol-sulfate) or poly(diallyldimethylam-moniumchloride), are used to quantify the concentration of polycation or polyanion, hence relying on a 1 1 stoichiometry. Using the cationic dye, tol-uidine blue, as an indicator, a metachromatic end point is detected. Both methods are volumetric. 

In a potentiometric titration, only the changes in Eceii or pH (AE or ApH) with titrant addition are important. The position of the Eceii-oersus-titrant-volume curve relative to the vertical axis (the EceU axis) may vary with variations in Ejunction, Eref, nature of the solution, etc. For a particular titration, however, its position relative to the horizontal axis (the titrant volume axis) does not vary. The equivalence point for the particular titration is thus fixed relative to titrant-volume axis, regardless of its position with respect to the EceU axis. In a simple pH potentiometric titration, where only the endpoint(s) may be required, it is not really necessary to cahbrate the glass electrode unless there have been indications that its significant characteristics such as hnearity and asymmetry have shown recent deterioration. 

Banik [166, 167]. The acidic properties of Na2B407 were studied by the potentiometric titration method using NaOH and Na2C03 as base-titrants, and the equilibrium oxide ion molality was detected by the potentiometric cells with the membrane oxygen electrode Pt(02)lYSZ. The process of titration was performed both from the acid to the base and from the base to the acid. The most characteristic potentiometric curves and the dependencies of the ligand number on the titrant molality are presented in Fig. 1.2.13. 

The potentiometric titration method possesses some advantages characteristic of potentiometry. The measured e.m.f. values are dependent on the logarithm of the activity (concentration) of the potential-defining ion and this considerably widens the range of concentrations which can be detected. The experimental techniques and routine are rather simple and the obtained results are well reproducible. Owing to the stable activity coefficients of metal cations the measurements can be performed in sufficiently concentrated solutions of the corresponding metal halides. Performing the measurement does not imply any interference in the acid-base processes in the melt studied and the experiment is faster than the isothermal saturation technique discussed above. 

If, under the titration conditions, there is the formation of a moderately soluble oxide, either in the dissolved state or as a precipitate then the treatment of the results has been shown in Section 3.7.3 to become very complicated, mainly because the potentiometric titration curve does not include any characteristic sections, apart from the initial sharp decrease in e.m.f. (pO), which is gradually transformed to a flatter dependence. The pO drop at the equivalence point is often absent and both p Meo and p MeO are subject to a small directed shift. A question arises of how to determine whether the... 

From the known values of the plots of the dependence of solubility on the particle-sizes for the oxides studied we can calculate the molar surface area of the oxide particles which are precipitated from the saturated solutions obtained under the conventional potentiometric titration conditions. The results of these calculations are presented in Table 3.7.9. From these data, it follows that the oxide particles deposited under the conditions of potentiometric titration are characterized by considerably higher molar surface areas than with the commercial oxide powders. We now compare these values the commercial calcium oxide used possesses a molar surface area of 594 m2 mol-1 against 780 m2 mol-1 characteristic of the... 

Potentiometric titration experiments of Zr chloride, nitrate, sulphate and perchlorate solutions were conducted at (25.00 + 0.05)°C until the onset of precipitation. Initial solutions (0.038, 0.019, 0.0095 and 0.0047 M in Zr) contained < 0.4% Hf and had an excess of 2 M of the acid of the anion studied. Titrations were performed with carbonate free 0.101 N NaOH. Glass electrodes where calibrated regularly but no correction for differences between liquid junction potential of reference and measured solutions was performed. The pH convention used was not reported and it is assumed that a NBS type convention was used. The pH at the onset of precipitation and coagulation of an uncharacterised and presumably amorphous solid were determined optically. The pH of coagulation was the pH at whieh the precipitate coagulated and the supernatant solution was clear. Reproducibility of these characteristic pH values was within 0.05 to 0.07 pH units. 

When experimental methods to measure proton affinity distribution spectra (PADs) from potentiometric titration data became available [54a], it was found by Contescu et al. [58] that the apparent values of proton binding constants identified from PADs were in semiquantitative agreement with log K values for binding predicted by the MUSIC model (Table 1). The characteristic PADs for several oxides are shown in Fig. 2. 

The characteristics (pH and length of the plateau in potentiometric titration curves) have already been shown to depend on factors that usually affect both the globules and the extended macromolecules (polymer and salt concentrations, presence of organic solvent, nature of the alkyl substituent of nitrogen atoms).2 4 Another factor which might be important is the nature of the polymer backbone. 

Figure 7-11 is a comparison of the pH-potentiometric titration behavior of three surface archetypes (Fig. 7-1 la) a colloidal metal oxide-hematite (oc-Fe203) (Fig. 7-1 lb) a natural organic matter (NOM) Suwannee River humic acid, and (Fig. 7-1 Ic) a Gram-negative bacteria (Desulfovibrio vulgaris). While there are many other examples that might be brought to bear as representative colloid types, the three colloids described here exhibit the range of characteristics of colloids that can be found in systems of environmental relevanee. These three surface types also will be discussed in the Colloid Generation, Transport and Deposition section.

Potentiometric titration with HCl gives a characteristic value proportional to the content of amphoteric surfactant (1,10,11). In some cases, solvent systems have been optimized so that acid-base titration is suitable for assay of the product, as described below for characterization of alkylbetaines (12). 

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