EDTA solutions composition

Standard EDTA Solutions. Disodium dihydrogen ethylenediaminetetraacetate dihydrate is available commercially of analytical reagent purity. After drying at 80°C for at least 24 hr, its composition agrees exactly with the dihydrate formula (molecular weight 372.25). It may be weighed directly. If an additional check on the concentration is required, it may be standardized by titration with nearly neutralized zinc chloride or zinc sulfate solution. 

Fig. 3. Current-potential curves for anodic oxidation of H2CO on different metals. Dotted lines current attributable to the anodic dissolution of Cu and Co electrodes. Solution composition 0.1 mol dm-3, 0.175 mol dm 3 EDTA, pH = 12.5, T — 298 °K. Adapted from ref. 38.

Industrially, the silver is recovered from either the wash water, or the bleach fix separately or from a mixture of the two using electrolysis employing a stainless steel cathode cylinder and an anode of stainless steel mesh. A typical wash solution composition contains silver (4 g L ), sodium thiosulphate (220 g L ), sodium bisulphite (22 g L ) and sodium ferric EDTA (4 g L ). At Coventry we have used a scaled down version of the industrial process employing 250 mL samples [46]. Electrolysis experiments were performed at ambient temperature with both wash and bleach fix solutions and in which the potential applied to the cathode and the speed of rotation of the cathode were varied. The sonic energy (30 W) was supplied by a 38 kHz bath. The results are given in Tab. 6.9. The table shows that the recovery of silver on sonication of the wash or bleach fix solutions is much improved especially if the electrode is rotated while ultrasound is applied. Yields with bleach fix (which contains ferric ions) are less since Fe and Ag compete for discharge (Eqs. 6.13 and 6.14). 

Only two papers on CD of an arsenic chalcogenide (arsenic sulphide) were found. Films were obtained using thiosulphate in an EDTA solution of AS2O3 at room temperature and a pH of 2-3 [9]. No compositional information was given. A bandgap of 2.0 eV and a resistivity of O-cm were measured. 

Figure 2.21. Composition of EDTA solutions as a function of pH (from Skoog and West, 1976, with permission).

Figure 1 7-2 Composition of EDTA solutions as a function of pH. Note that the fully protonated form, H4Y is only a major component in very acidic solutions (pH < 3). Throughout the pH range of 3 to 10, the species H2Y and HY - are predominant. The fully unprotonated form Y is a significant component only in very basic solutions (pH > 10).

A 0.3284-g sample of brass (containing lead, zinc, copper, and tin) was dissolved in nitric acid. The sparingly soluble SnOi -4H20 was removed by filtration, and the combined fdtrate and washings were then diluted to 500.0 mL. A 10.00-mL aliquot was suitably buffered titration of the lead, zinc, and copper in this aliquot required 37.56 mL of 0.002500 M EDTA. The copper in a 25.00-mL aliquot was ma.sked with thiosulfate the lead and zinc were then titrated with 27.67 mL of the EDTA solution. Cyanide ion was used to mask the copper and zinc in a 100-niL aliquot 10.80 mL of the EDTA solution was needed to titrate the lead ion. Determine the composition of the brass sample evaluate the percentage of tin by difference. 

The fraction of free EDTA in the form called ay -, is shown by the colored curve in Figure 13-7. At pH 6.00 and a formal concentration of 0.10 M, the composition of an EDTA solution is... 

Pretsch and co-workers demonstrated for the first time that a detection limit of liquid membrane ISEs can be as low as the picomolar range by controlling the transmembrane flux (54). Figure 7.14 shows the responses of the same Pb -selective electrodes with different inner solution compositions. When Pb is buffered in the inner solution containing EDTA, the detection limit can be improved by almost five orders of magnitudes down to -10" M. The low Pb + concentration in the inner solution suppresses the co-extraction... 

Defect concentrations of Fe in Fei xO are usually measured by chemical analysis. It is impossible to determine the compositions of non-stoichiometric compounds, because the error of an ordinary quantitative analysis is about 10, while the deviation of a crystal with intrinsic defect from its stoichiometric composition is about <10. Nevertheless, it is possible for chemical analysis to determine if the metal atoms in non-stoichiometric compounds are excessive or less. Because a non-stoichiometric compound, in common, is a multi-component solid solution in which the different components have different valences, e.g., Fei xO can be viewed as a solid solution which consists of Fe +O and Fe2" 03. Deviation of those types of compounds can directly be determined by measuring of the concentration of an atom that shows an abnormal valence in it. For example, it forms the solutions containing large amounts of Fe + ion and less amounts of Fe + ion, when Fei xO (catalyst) is solved by hydrochloric acid solution under conditions with the absence of air or oxygen. Among these ions, the contents of both Fe + and Fe + can be determined by a titration of EDTA, but the Fe + needs to be oxidated to Fe + by ammonium persulfate prior to titration. The volume ratio of EDTA solutions that are consumed by Fe + and Fe + ions respectively is the ratio of Fe + and Fe + in sample, namely defect concentration of Fe, i.e., x = 1/(3 - - 2Fe +/Fe +). There is also Kulun titration or polarographic analysis except for oxidation-reduction titration which can be used for such measurement of an ion with abnormal valence in the solution of a solid sample. 

Experimental results of synthetic powder Fe O dissolution rates in formic, oxalic and citric acids, EDTA and their mixtures depending on agent concentrations, pH, etc. were investigated and compared. Comparison of these results with stabilised chemical equilibriums in solutions and distribution diagrams of particular complexes enabled optimization of decontamination solution composition for decontamination objectives during decommissioning. 

Takahashi et al. [220] first reported the formation of Bi-Te alloy films with varying chemical composition by means of cathodic electrodeposition from aqueous nitric acid solutions (pH 1.0-0.7) containing Bi(N03)3 and Te02. The electrodeposition took place on Ti sheets at room temperature under diffusion-limited conditions for both components. In a subsequent work [221], it was noted that the use of the Bi-EDTA complex in the electrolyte would improve the results, since Bi " is easily converted into the hydrolysis product, Bi(OH)3, a hydrous polymer, thus impairing the reproducibility of electrodeposition. The as-produced films were found to consist of mixtures of Te and several Bi-Te alloy compounds, such as Bi2Tc3, Bi2+xTe3 x, Bi Tee, and BiTe. Preparation of both n- and p-type Bi2Te3 was reported in this and related works [222]. 

A detailed physical examination of the purple complex formed in alkaline solution between Fe(III), ethylenediaminetetraacetic acid (EDTA) and peroxide shows it to have a composition [Fe "(EDTA)02] (togA, 3 c =4.33). This complex catalyses decomposition of peroxide, the rate-pH profile going through a maximum at pH 9-10 . 

It is possible to determine the concentration of certain metal ions by performing a titration in which the complexation of the metal is the essential reaction. Typically, a chelating agent such as EDTA is used because the complexes formed are so stable. The specific composition of complexes formed in solutions often depends on the concentrations of the reactants. As a part of the study of the chemistry of coordination compounds, some attention must be given to the systematic treatment of topics related to the composition and stability of complexes in solution. This chapter is devoted to these topics. 

ID Considering just acid-base chemistry, not ion pairing and not activity coefficients, find the pH and composition of 1.00 L of solution containing 0.040 mol H4EDTA (EDTA = ethylenedinitrilotetraacetic acid = H4A). 0.030 mol lysine (neutral molecule = HL), and 0.050 mol NaOH. 

Foreign ions are masked with a composite EDTA-sodium hexametaphosphate reagent and interference by sulfide is overcome by the addition of mercuric chloride, which also mitigates interference by thiosulfate, sulfate, tetrathionate and iodide, and the precipitated mercuric sulfide is filtered off prior to the addition of chromogenic reagents and spectrophotometry. Beer s law is obeyed up to levels of 20 p,g nitrite in a 60 ml test solution. 

The retardation factors of the four radioelements for four hypothetical HLW compositions were derived using the prediction equations. (The retardation factor is the ratio of the solution velocity to the radioelement velocity in a system of solution flow through a porous medium and increases linearly with Kd.) The four hypothetical HLW solutions broadly represented dilute/non-complexed, dilute/complexed, concentrated/noncomplexed, and concentrated/complexed HLW. Dilute waste had low concentrations while concentrated waste had high concentrations of Na+, NaOH, and NaAlO,. Non-complexed waste had no HEDTA or EDTA while complexed waste had 0.1M HEDTA/0.05M EDTA. 

The chemical composition of the retrieval solution may affect the efficacy of the process and a wide variety of solutions have been advocated including citrate buffer, Tris buffer, glycine-hydrochloric acid, EDTA, urea, heavy metal solutions, and other proprietary reagents. The molarity of the solution may also significantly influence immunostaining (Taylor et al, 1996). 

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