Complexing agents, uses

SB Auxiliary complexing agent. Use the equation derived in Problem 12-18 for this exercise. 

The systems so far described can be expressed in terms of the general formula Cat+X z Y, where Cat+ is in principle any ammonium, phosphonium or sulfo-nium cation, X is generally a halide anion (usually Cl ). They are based on equilibria set up between X- and a Lewis or Bronsted acid Y, z refers to the number of Y molecules which complex X-. The ionic liquids described can be subdivided into three types depending on the nature of the complexing agent used. 

Fractional crystallization and precipitation are classical methods of separation of rare earth metal ions. Complex forming agents may be used to give better separations than simple or double salts. Some of the complexing agents used in fractionation separation are given below. 

The complexing agents used at Exxon are quaternary pyrrolidinium and morpholinium compounds. The bromine complex formed upon charge is a heavy insoluble oil which accumulates at the bottom of the catholyte reservoir (cf. Fig. 11) Complexing reduces the vapor pressure of bromine by one to two orders of magnitude, and the self-discharge rate, as well as corrosive bromine attack, are considerably diminished. 

Why is a complexing agent useful that can selectively and reversibly react with the solute of interest ... 

Increased selectivity has also been obtained using polyethylene glycol as complexing agent.Using toluene as solvent, the authors report a 1 10 para. ortho ratio in the formylation of phenol. 

Complexing agents used in coupled transport membranes are usually diluted with a carrier solvent, typically a mixed aliphatic-aromatic hydrocarbon. We would generally expect the amount of metal extracted by the complexing agent solution to increase with increasing agent concentration, and this is usually the... 

From this literature survey it appears that despite the appearance of a relatively large number of papers concerning chemical bath deposition, most are focused on a few materials, especially sulfide binaries such as PbS, CdS, which are used for applications. If we exclude these materials, in fact the work on other compounds is often limited to a few papers, or appears in screening studies. There is a trend towards the elaboration of ternary compounds by CBD, but the competition between the formation of the binaries represent a major difficulty. It seems that the composition of the solution, especially the nature of the complexing agents used plays a role. A general... 

Since many of the complexing agents used are themselves weak acids or bases control of pH is most important. The pH of the solution will in such cases control the stability of the complex and in turn the half wave potential of the resultant wave. The effectiveness of a complexing agent to resolve the waves for two metallic ions will often require a particular pH range to be chosen. 

Other complexing agents used to eliminate or reduce the influences of metal ions on the determination of hydride forming elements are cyanides, thiocyanates, tartaric acid, citric acid, ammonium fluoride, and 2-mercapto-propionic acid. 

Chem. Descrip. Neutralized complexing agent Uses Wetting agent, dispersant for water-based varnishes, highly pigmented slurries binder Properties Water clear thin liq. 50% cone. 

A series of ions (Pd(II), Bc(II), Ga(in), Fe(III), AI(III) and Cu(II)) were extracted from water as their acetylacetone complexes and baseline resolved on a C g column (A = 330nm) using a 58/35/6/1 methanol/water/dichloromethane/acetic acid mobile phase [151]. Elution was complete in 40 min and detection limits of 1-5 ppb were reported. Peak shapes were uniformly good. The authors used this technique to determine Cu(II) and Fe(III) levels in tap water. It should be noted that other ]3-diketone complexing agents, used like ion pair reagents, should also be eflective here. 

TabI I. Complexing agents used for the determination of itietal ions by adsorptive stripping voltammetry... 

One of the major applications of pM buffers is in maintaining concentrations of necessary metal ions in biological nutrient media at essentially constant levels. As free metal ions are removed from the system, perhaps by hydrolysis or by incorporation into metalloenzymes, they are replenished by the reversible dissociation from a reservoir of metal complex. Among the first complexing agents used in this way were citrate and tartrate ions, but more recently aminopoly-carboxylic acids such as ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA) and nitrilotriacetic acid (NTA) have become the chelating agents... 

Figure 5.4.2. Examples of complexing agents used to bind metals (shown attached to polymers).

Because the three sol-gel methods (alkoxide, metal complex, and Pechini) are so closely related, it is relatively easy to combine them to generate novel synthesis routes. For example, several authors describe the mixture of metal complex solutions with the alkoxide tetraethyl orthosiUcate to synthesize Li2FeSi04 [19,20]. Table 36.2 is a survey of recent reports of LIB materials synthesized by sol-gel routes. Table 36.2 is organized by foiu- basic characteristics of each report the composition of the final insertion material, the type of complexing agent used... 

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