Adsorption indicator cationic

Discussion. The method is applicable to the determination of a mixture of two salts having the same anion (e.g. sodium chloride and potassium chloride) or the same cation (e.g. potassium chloride and potassium bromide). For example, to determine the amount of sodium and potassium chlorides in a mixture of the two salts, a known weight (Wj g) of the solid mixture is taken, and the total chloride is determined with standard 0.1 M silver nitrate, using Mohr s method or an adsorption indicator. Let w2 g of silver nitrate be required for the complete precipitation of Wj g of the mixture, which contains xg of NaCl and yg of KC1. Then ... 

Figure 3.26. Gibbs energy per unit area of double layers with specific adsorption of cations at the outer Helmholtz plane. The combinations of inner layer capacitance c and K are given. Symmetrical (1-1) electrolyte.

Situation b of fig. 3.34 is more common and is indicative of specific adsorption of cations. (For specific adsorption of anions the intersection points... 

Naturally, for adsorption on cations in zeolite voids, which we have called electrostatic adsorption, the concept of the invariance of characteristic curves is a rather crude approximation. This is directly indicated by characteristic curves constructed from experimental adsorption isotherms for a sufficiently wide temperature range. However, for the purposes of practical description of adsorption equilibria, such an approximate assumption in a controlled temperature range is reasonable. A general evaluation will be made below. 

An adsorption indicator is typically an organic dye, such as fluorescein and its derivatives. Most adsorption indicators are weak acids. Their use is thus confined to basic, neutral, or slightly acidic solutions in which the indicator exists predominantly as the anion. Some cationic adsorption indicators are suitable for titrations in strongly acidic solutions. In this case, adsorption of the dye and coloration of the precipitate occur if the precipitate particles possess a negative charge. 

Temperature the results compiled in Tables 4.1-4.6 were obtained at different temperatures, and in some studies the temperature was not controlled. The results reported in Table 3.11 and Fig. 3.104 indicate that the PZC of oxides and related materials shifts to low pH when the temperature increases (with a few exceptions). Most surfaces carry more negative charge at elevated temperature (at given pH), and this creates favorable conditions for adsorption of cations and unfavorable conditions for adsorption of anions. Therefore elevated temperature would enhance uptake of cations, and low temperature would enhance uptake of anions at constant pH, if the electrostatic interaction was the only factor. On the other hand, the rate of chemical reactions and diffusion is enhanced at elevated temperatures. Thus, the kinetic and electrostatic effect on cation adsorption add up and the uptake increases with temperature. With anions these effects act in opposite directions the uptake increases with temperature when the kinetic factor prevails the uptake decreases with temperature when the electrostatic factor prevails, finally the both effects can completely cancel out. 

Thus, a few results indicate that the electrokinetic behavior of metal oxides at high concentrations of 1-1 electrolytes is similar to that at low ionic strengths that is, the increase in electrolyte concentration depresses the absolute value of the potential, and the IEP remains unaffected. In a few other studies, a shift in the IEP to high pH was observed at concentrations of 1-1 electrolytes of about 0.1 M. Such a shift suggests specific adsorption of cations. 

On a short timescale (seconds to minutes), illuminated OCP analysis is a nondestructive technique for most materials. However, extended periods of illumination at open-circuit conditions may lead to corrosion of the photoelectrode surface [2]. Therefore, it is best to minimize the time of exposure to high-intensity illumination. Intense illumination can heat the solution (especially if the infrared radiation is not pre-filtered) at the electrode surface, which can cause a slow drift of the measured potential over the course of seconds or hours, depending on the rate of heating. In addition, drifts in the potential response may also be the result of corrosion processes or slow adsorption of cations or anions in solution to the semiconductor surface. A more rapid photovoltage response is often desirable and can be indicative of a better material. 

The dissociability of the adsorbed salt is also important. Adsorption decreases as the degree of dissociation of the adsorbed salt increases. The deformability of the foreign ion also has an influence. With anions, which are generally more easily deformed than cations, the deformability increases with size. Dyestuff anions, for example, are highly deformable and this property is utilized in the application of adsorption indicators used in volumetric analysis. 

Adsorption indicators were first introduced by Fajans for the detection of endpoints of precipitation titrations, particularly in argentimetry. Any substance that forms a deformable anion or cation exhibiting different colors in solution and when adsorbed may be capable of functioning as an adsorption indicator in a precipitation titration. Since any large ion is... 

Direct evidence of the adsorption of cationic polymers on skin from an anionic surfactant system has been reported by Goddard and Leung (20). The authors determined the uptake of Polymer JR 125, on stratum corneum (SC) in the presence of three anionic surfactants [SDS, alfa olefin sulfonate (AOS), and alkyl 2EO sulfate] and a coco-betaine surfactant. Even though the conditions involved 30 min of exposure to the substrate, the results obtained are indicative of the trends that can be expected under normal conditions. The results reproduced in Figure 3 show that the uptake of the polymer is initially reduced markedly by the surfactants. Interestingly, at surfactant concentrations above about 10%, the polymer uptake in fact increases and at 20% the extent of uptake is in fact higher than that obtained in the absence of the surfactant. Note that the surfactant concentrations are... 

In an early work by Petzold and Lunkwitz [9], this efficiency of recharging of the fibres using cationic complexes of poly(diallyldimethylammonium chloride), PDADMAC, and poly(maleic acid-co-a-methylstyrene), MS-a-MeSty, was used to flocculate cellulose fibres, but the actual adsorption of the complexes was not measured. The adsorption of anionic complexes of polyethyleneimine (PEI) and CMC on fibres pretreated with a cationic PDMDAAC has also been studied by Hubbe et al. [24]. These authors found that when the charge of the complexes was decreased there was an increase in adsorption, indicative of an electrosorption process, but the authors also detected signs of nonionic interaction although they were not able to establish the molecular reason for this behaviour. 

Unlike cations, the adsorption activity of CT, Br", and I at Pt electrodes is appreciable806 and increases in the given sequence of anions. At a 0, the <7, A curves for LiC104, NaCl,NaBr, and Nal coincide, which indicates that complete desorption of halide ions takes place at negatively charged surfaces. The values of Ea=0 for a renewed Pt electrode have been found to be -0.18, -0.24, and -0.33 V (SCE in H20) for NaCl, NaBr, and Nal in DMSO, respectively. 

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