Determination of chlorides and bromides

Akaiwa et al. [324] have used ion exchange chromatography on hydrous zirconium oxide, combined with detection based on direct potentiometry with an ion selective electrode, for the simultaneous determination of chloride and bromide in non saline waters. 

The cyanide ion is isoelectronic see Isoelectronic) with CO, N2 and NO+, with an electronic configuration of (la) (2a)2(3a) (4cr) (l7r)" (5a) this corresponds to a triple bond (one a-bond see a-Bond) and two tt-bonds see n-Bond)) between the carbon and nitrogen atoms. A lone pair see Lone Pair) of electrons is present on both atoms in CN. Calculations have indicated that the negative charge of the cyanide ion is shared approximately equally between the two atoms. The carbon-nitrogen triple bond distance is 1.16 A in the free cyanide ion the fundamental vibrational frequency of the C N bond (aqueous solution) is 2080 cm. The effective Crystallographic Radius of CN, as determined in cubic alkali metal cyanides, is 1.92 A this value is intermediate between those of chloride and bromide. 

In studies of rates of iodine hydrolysis in the presence of chloride and bromide ions step (1) was also suggested as rate-determining (in iodate formation at pH 6-8). 

Lybrand, T. P., I. Ghosh and J. A. McCammon (1985). Hydration of Chloride and Bromide Anions Determination of Relative Free Energy by Computer Simulation. J. Am. Chem. Soc. 107 7793-7794. 

Besides the weakness of complex formation, the simultaneous presence of inner- and outer-sphere complexes, especially in the cases of chloride and bromide, further complicates the determination of the correct solution speciation. Using most of the experimental methods the measured formation constant is the sum of the formation constants of two types of complexes, [NiL(H,Q),l and [Ni(H20) L] , ... 

Figure 10.28b illustrates the performance of the method for the determination of oxyhalides and bromide in a drinking water sample spiked with chlorite, bro-mate, bromide, and chlorate at levels of 108, 11.3, 36, and 72pg/L, respectively. Quantitative recoveries between 96 and 107% were obtained for all anions. As can be seen for the UV/Vis trace in Figure 10.28b, no response is observed for the large peak of chloride (c = 20 mg/L) that elutes immediately after bromate. 

ICP-MS methods Chlorine, bromine, and iodine were measured by Tagami et al. [50] in aqueous samples using inductively coupled plasma-mass spectrometry (ICP-MS). Since iodine has only one stable isotope, m/z = 127 was scanned for iodine determination. For chloride and bromide determination m/z of 35 and 79 were, respectively, applied. Cesium (m/z = 133) was used as an internal standard during ICP-MS determination to monitor the change in counting efficiency. 

Iodide ions can be determined quite well with argentimetric titrations. The Volhard method, electrometric endpoint indications, and adsorption indicators work well. The Mohr endpoint indication, however, does not give good results because of the adsorption of the chromate on the silver iodide precipitate. The presence of chloride and bromide ions disturbs the argentimeric iodide determination. 

Salt Effects. In the low salinity region, the charge on the polymer determines the slope (Figure 6), and the acetate content changes the T by about 15 C per mole/repeat unit. We have obtained data for solutions of higher salinity. Not only have we looked at sodium chloride, but also salts such as calcium chloride and bromide which are used in heavy brines for drilling and workover operations. 

The application of the Chelex 100 resin separation and preconcentration, with the direct use of the resin itself as the final sample for analysis, is an extremely useful technique. The elements demonstrated to be analytically determinable from high salinity waters are cobalt, chromium, copper, iron, manganese, molybdenum, nickel, scandium, thorium, uranium, vanadium, and zinc. The determination of chromium and vanadium by this technique offers significant advantages over methods requiring aqueous final forms, in view of their poor elution reproducibility. The removal of sodium, chloride, and bromide allows the determination of elements with short and intermediate half-lives without radiochemistry, and greatly reduces the radiation dose received by personnel. This procedure was successfully applied in a study of... 

The self-ionisation of aluminium chloride and bromide in nitrobenzene has been studied in great detail [15], and the rates of the forward and back reactions have been determined so that all the relevant equilibrium constants are known. The whole body of evidence available shows that self-ionisation of the initiator, with or without other ionogenic reactions in the initiator solutions, can be regarded as well established for all aluminium halides and as highly probable for the alkyl aluminium halides. Moreover, the ionogenic reactions are relatively slow and - except under the dirtiest conditions - the concentration of ions in the initiator solution will be very much less than [A1X3]0. 

Halohydrin dehalogenase activity was determined by monitoring halide liberation at 30 °C in tris-S04 buffer (50 mM, pH 8.0) containing 5 mM 1,3-dichloropropanol or 1,3-dibromopropanol as the substrate. All buffers used for activity assay were prepared with bidest water. From the incubation mixture, 0.5 ml samples were taken and mixed with 1.6 ml of H2O, 0.2 ml or halide reagent 1 and 0.2 ml of halide reagent II. Absorbances were read at 460 nm. A calibration curve of 0-1 mM of chloride or bromide was used to calculate the concentration of halide. The extinctions at 460 nm should be below 0.4 (for chloride) or 0.8 (for bromide). 

The bromyl ion decomposes spontaneously. Chloryl and iodyl ions were studied through their attack on chloride and bromide ions respectively. By determining the rate of disappearance of dichromate and using an analysis similar to the pyrosulfate-nitrate case, the following equilibrium constants were found for the dichromate-halate reactions which produce halyl and chromate ions (not calculated as BaCrC>4, but as [Cr04 2] in solution) (2). 

Oxidation-Reduction Titrations. The extent of reduction resulting from reaction of niobium (V) chloride and bromide with pyridine was determined by indirect titration of crude reaction mixtures with standard ammonium tetrasulfato-cerate(IV) solution. Samples were stirred overnight in a stoppered flask with an excess of iron (III) ammonium sulfate. Any iron (II) formed by reaction with the niobium complex mixture was then titrated with the standard tetrasulfato-cerate(IV) solution using ferroin as indicator. Results of these determinations are given in Table III. 

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