Potassium Bromide Solution Research Articles

Development of a new bulk optode membrane for the determination of mercury(II)

A new procedure for constructing an optical fibre reflectance sensor of the bulk optode membrane type is presented. The optode membrane consists of a plasticized poly(vinyl chloride) (PVC) membrane in which the ionophore is dissolved, entrapped in a cellulose support. The new optode with the metallochromic indicator, 1-(2-pyridylazo)-2-naphthol (PAN), was incorporated into a newly designed flow-through cell and the injection system was optimized for the determination of Hg(II) at 560 nm in the range 2–200 mg l −1 (10 −5–10 −3 M) with a detection limit of 0.11 mg l −1 Hg(II). The coefficients of variation of the sensor response for 10 and 40 mg l −1 of Hg(II) were ±2.57 and ±0.88%, respectively, and the CV between four membranes was ±3.5%. The sensor can readily be regenerated with the carrier, potassium bromide solution. The optode is fully reversible. The method was applied to the determination of mercury in an alloy for dental prosthesis and to the indirect determination of sulphite in aqueous solutions.

Solid-phase extraction and spectrophotometric determination of hydrogen sulfide in air and water utilizing ethylene blue formation

Hydrogen sulfide in water stabilized with or absorbed from air in an alkaline mixture of zinc acetate and EDTA was treated with 4-N,N-diethylaminoaniline and iron(III) in sulfuric acid medium and the absorbance of ethylene blue was measured at 670 nm after 5 min. The molar absorptivity was found to be 9.42 × 105 l mol−1 cm−1. The ethylene blue dye could be preconcentrated by solid-phase extraction on a CN sorbent and eluted by potassium bromide solution in water–methanol leading to an enrichment factor of at least 50. Coloured samples were subjected to clean-up by using Lichrolut EN and the colourless eluate was treated for colour development. Rectilinear calibration graphs were obtained over the range 10–800 μg l−1 sulfide (r = 0.9997) without solid-phase extraction, and 1–100 μg l−1 sulfide (r = 0.9989) after solid-phase extraction of the dye. The limits of detection were 5 μg l−1 and 0.2 μg l−1 sulfide without and after solid-phase extraction, respectively. The interference of up to 100 mg l−1 thiols, 50 mg l−1 sulfite and 10 mg l−1 thiosulfate could be avoided by their masking with N-ethylmaleimide. Up to 10 mg l−1 fluoride and 100 mg l−1 thiocyanate did not cause any interference. Interference of up to 100 mg l−1 fluoride was avoided by masking with zirconyl nitrate. The method has been validated by analysing spiked river water samples, when the average recovery was 99% (range 96–104%) with an RSD of 3% (range 2–4%). Sulfide has been detected in many river waters at low μg l−1 levels.

Morphology and twin plane structure of silver bromide rod crystals

Large silver bromide rod crystals have been grown in a solution of silver bromide and potassium bromide in dimethyl sulfoxide. Samples of these crystals were examined by scanning electron microscopy in order to study their side and top face structure. Crystal sides were bounded by {111} and {100} faces. Rod crystals grown from concentrated solutions developed a well-defined top face structure composed of alternating {111} and {100} faces. However, they showed a relatively small length to thickness ratio. On the other hand, top faces of fast growing rod crystals were rough. Slices of rod crystals were examined by transmission electron microscopy to study their twin plane structure, for the first time. All the rod crystals examined showed non-parallel twin planes of (111) type. Surprisingly, all of them also showed parallel twin planes. Rod crystals can transform into tabular or tetrahedral crystals either by formation of new twin planes, or by overgrowth of some twin variants over others in processes that start at the tips of the rod.

Design and self-assembly of open, regular, 3D mesostructures

Self-assembly provides the basis for a procedure used to organize millimeter-scale objects into regular, three-dimensional arrays ("crystals") with open structures. The individual components are designed and fabricated of polyurethane by molding; selected faces are coated with a thin film of liquid, metallic alloy. Under mild agitation in warm, aqueous potassium bromide solution, capillary forces between the films of alloy cause self-assembly. The structures of the resulting, self-assembled arrays are determined by structural features of the component parts: the three-dimensional shape of the components, the pattern of alloy on their surfaces, and the shape of the alloy-coated surfaces. Self-assembly of appropriately designed chiral pieces generates helices.

Anion and cation leaching through large undisturbed soil cores under different flow regimes. 1. Experimental results

The movement of anions and cations under different unsaturated flow regimes was studied in 2 large undisturbed cores from a soil under pasture. Sequential leaching of calcium sulfate (CaSO4) and potassium bromide (KBr) solutions was carried out at water fluxes which ranged from a normal 5–20 mm/h rate in one core (the slow flow core), to unusually high values up to 350 mm/h in the other (the fast flow core). The objective was to examine the leaching behaviour of the applied cations and anions under these contrasting flow conditions, and determine the relative influence of soil physical and chemical processes in governing ion movement. A better understanding of this behaviour should help in the development of improved practices to reclaim saline soils, ameliorate sodic soils, and minimise unwanted leaching of nutrients. In the slow flow core, miscible displacement breakthrough curves (BTCs) were observed for bromide, with sulfate movement retarded relative to the bromide. Cation exchange reactions occurred in the slow flow core, with calcium generally the dominant cation balancing anions during their movement through the soil. When KBr solution was substituted for CaSO4, potassium ions replaced calcium ions on the exchange sites, resulting in an increase in the calcium concentration in the effluent. In the fast flow core, however, flow was highly preferential and the water flux very variable. The surface-applied solutes appeared very rapidly in the effluent, irrespective of whether they were cations or anions. Under these conditions, solution cation/anion interactions with the soil surfaces did not appear to approach equilibrium, so that the leaching process was dominated by the soil’s water flow characteristics and showed little influence of surface chemical reactions.

Stress optical coefficient of viscoelastic solutions of cetyltrimethylammonium bromide and potassium bromide

The rheo-optical properties of different viscoelastic solutions of surfactant are investigated in order to gather experimental data which allow for the computation of the stress optical coefficient C.

In situ observations of silver bromide tabular crystal growth

Nucleation and growth of silver bromide tabular crystals has been observed insitu for the first time by optical microscopy. Crystals were precipitated by a new method, from solutions of silver bromide and potassium bromide in DMSO. Thin tabular crystals were preferentially produced in a narrow range of silver concentration, after long nucleation periods. A twinning process occurred, generally, in a very early stage of the precipitation. Tabular crystals could appear in a single spot in the absence of other particles and they grew with a very high initial rate. Coalescence of particles was practically discarded as the main mechanism for twinning. Most tabular crystals were initially circular and then were transformed into hexagons or triangles as they developed six or three straight edges. A fast growth rate was associated with rough sides, while straight edges moved more slowly. Changes in crystal shape occurred during the growth process in a way similar to that found by Maskasky in aqueous systems by indirect mapping methods. Changes in crystal shape occurred by roughening on one, three or six crystal edges.

Optical and Rheological Properties of a Semi-Diluted Equimolar Solution of Cetyltrimethylammonium Bromide and Potassium Bromide

We report in this paper the results of rheological and optical experiments performed on a semi-diluted viscoelastic solution of cetyltrimethylammonium bromide (CTAB) in water with sodium bromide at a concentration of 0.3 M I- 1 in surfactant and salt. This concentration in surfactant is much smaller than the concentration which gives a nematic phase at rest. The solution behaves like a Maxwell fluid with a single relaxation time. When submitted to a shear flow, this solution shows a behaviour typical of a system undergoing a phase transition. When observed between crossed polarizer and analyzer, the gap of the Couette cell appears divided in two bands the optical properties of which are different; in rheology, the curves σ(γ) are also characteristic of these systems where the shear stress presents a plateau extending between two critical values, γ1c and γ2c of the shear rate. We finally compare the results with previous experiments performed on a concentrated solution of CTAB containing no salt.

Determination of organomercury compounds in aqueous samples by capillary gas chromatography-atomic fluorescence spectrometry following solid-phase extraction

A new method based on capillary gas chromatography-atomic fluorescence spectrometry (GC/AFS) is described for the determination of methylmercury (MeHg) and ethylmercury (EtHg) in water samples. An improved sample preparation methodology was developed, which involves preconcentration of the alkylmercury species from water samples, drawn with a 12 channel peristaltic pump, onto sulfhydryl cotton fiber (SCF) adsorbent packed in a screening column, elution of MeHg and EtHg with a mixture of acidic potassium bromide and copper sulfate solution, and back-extraction using methylene chloride. Analysis was performed by capillary GC/AFS with a DB-1 column. Some important parameters, including sample pH, presence of anions and cations, concentration of dissolved organic carbon (DOC), eluent type, and eluent volume were evaluated. With AFS as a detector, the capillary gas Chromatographic technique provides high selectivity, high sensitivity, and a straightforward method for organomercury halide analysis. It eliminates possible spectral interferences to the detector from other sample components and from chemicals used in the sample preparation procedure. The detection limit was 0.01 ng l −1 in a 11 water sample for both MeHg and EtHg. The result for organomercury analysis in a number of natural water samples is shown to illustrate the applicability of this method to real environmental samples.

Stress Corrosion Cracking of Silver-Gold Alloys in 1 M Potassium Chloride, Potassium Bromide, and Potassium Iodide Solutions

Abstract Silver-gold (Ag-Au) alloys (2.2 at% to 60 at% Au) were found susceptible to stress corrosion cracking (SCC) in 1 M potassium chloride (KCl), 1 M potassium bromide (KBr), and 1 M potassium ...

Effect of Charge Density on the Dynamic Behavior of Polyelectrolytes in Aqueous Solution

Dynamic light scattering experiments and measurements of surface tension and viscosity of aqueous solutions of poly(2-vinylpyridine) quaternized with ethyl bromide are carried out as function of the charge density and polyelectrolyte concentration (Mw = 2.9 × 105, Mw/Mn = 1.11; αe, degree of quaternization, 0.09 ≤ αe ≤ 0.46). The polyelectrolytes are dissolved in an aqueous solution of potassium bromide (cs = 1 × 10-2c+, c+ = 1 mol dm-3). Their concentrations c̄p are in the range 0.1c̄+ ≤ c̄p ≤ 27c̄+ (c̄+ = 1 g dm-3). The reduced variable Λ (=αecm/cs) is used to characterize the composition of the solutions (cm, molar volume concentration of the repeat unit of the polymer backbone). Monomodal and bimodal dynamic modes characterized by the apparent diffusion coefficients Ds and Df (index s, slow; index f, fast) are found under the following conditions: monomodal, 0.03 ≤ Λ ≤ 0.1; bimodal, 0.1 ≤ Λ ≤ 8. A third dynamic mode characterized by the apparent diffusion coefficient Dint (index int, intermediate) appears at Λ ≳ 1 with small values of αe in the range 0.09 ≤ αe ≤ 0.15 (Ds < Dint < Df). It is assumed that the third mode reflects dynamic properties of hydrophobic domains formed by uncharged segments of the polymer backbone at low values of αe. Hydrophobic interactions show up also in surface tension and viscosity measurements. A model proposed by Lee and Schurr (J. Polym. Sci. 1975, 13, 873) describes the experimental Df data of the fast diffusive mode with two fit parameters (Zeff, effective number of charges of a polyion; Dp, diffusion coefficient of a polyion). Zeff is smaller by a factor of 5−7 than the value calculated on the basis of αe.

Determination of mercury in slurried samples by both batch and on-line microwave digestion–cold vapour atomic fluorescence spectrometry

An on-line microwave digestion system for the determination of total mercury in solid environmental samples was developed. The slurried samples were injected into a carrier stream of hydrochloric acid and mixed with a solution of potassium bromide–bromate before passing through a PTFE coil situated in the microwave cavity of the microwave digester. During the microwave digestion process, the mercury species were liberated from the sample matrix and full oxidation of organomercury compounds to HgII was achieved. After mixing with a solution of hydroxylammonium chloride, to remove the excess of bromine, the determination of mercury was undertaken by on-line cold vapour atomic fluorescence spectrometry. The developed system offers a rapid and sensitive method for the determination of mercury in solid environmental samples with a sample processing time of 50 s and a limit of detection of 13 ng l–1. In addition, a batch method utilizing open focused microwave digestion, in which samples were digested with a mixture of hydrogen peroxide and nitric and sulfuric acids, was developed. Both methods were validated using the National Research Council Canada certified reference materials DORM-2 and PACS-1 and gave results in good agreement with the certified values.

Electrochemical intercalation of bromine into graphite in an aqueous electrolyte solution

By electrochemical oxidation of a graphite sheet in an aqueous solution of potassium bromide, the intercalation of bromine was observed. It was confirmed by the measurements of weight increase of about 10%, decrease in relative electrical resistivity down to 0.69, and enlargement of average interlayer spacing. On the graphite sheet pre-electrolyzed in KBr solution, the chronopotentiogram in K 2SO 4 aqueous solution showed some plateaux corresponding to the reduction of graphite intercalation compounds with bromine. The longest time on a plateau was observed on the graphite sheet pre-electrolyzed in a potential region of bromine gas evolution, where the most pronounced decrease in electrical resistivity of graphite sheet was detected.

Fluorescence quenching method for the determination of atmospheric ozone using 2′,7′-dichlorofluorescein

A highly sensitive and selective fluorescence quenching method has been developed for the rapid determination of atmospheric ozone with 2′,7′-dichlorofluorescein as fluorogenic reagent ( λ ex = 505 nm, λ em = 520 nm) at pH 4.0–6.0. Ozone is collected in a solution of potassium bromide giving bromine (Br 2), which is estimated by the fluorescence quenching method using 2′,7′-dichlorofluorescein. Bromine may be used for calibration because the relationship between this compound and ozone has been determined. The calibration graph is linear over the range 10–50 μg per 25 ml ozone. The detection limit is 0.01 μg per 25 ml ozone. Nitrogen oxide does not interfere with the method. The method has been applied successfully to the determination of atmospheric ozone.

Determination of bromate in bread by capillary gas chromatography with a mass detector (GC/MS).

A sensitive method was developed for the determination of bromate in bread by capillary gas chromatography with a mass detector (GC/MS). Bromate was extracted with water from bread samples. After centrifugation, the supernatant was filtered and Cl- was removed by an OnGuard-Ag cartridge column. The mixture was absorbed on a DEA solid phase extraction column and washed with water. Bromate was then eluted with 3 M potassium chloride solution. Two ml of 4 x 10(-3) M styrene monomer solution (washed with 1% sodium hydroxide solution before use), 1 ml 0.01 M potassium bromide solution and 1 ml sulphuric acid were added to the eluent and shaken vigorously. The styrene bromo derivative (alpha-bromomethyl-benzenemethanol[2-bromo-1-phenylethanol]) was extracted with 2 ml n-hexane, and determined by GC/MS. Recoveries of bromate from breads were in the range 91.3-98.1% (0.03-0.50 micrograms/g), and the limit of detection was 0.03 microgram/g. Pullman and open top types of white bread, produced by a sponge and dough method and a short process method respectively, were prepared in our laboratory for measurement of residual bromate. When 30 micrograms/g or less bromate as HBrO3 (pullman type), and 75 micrograms/g bromate or less as KBrO3 (open top type), was added to flour, no residual bromate was detected in either type of bread.

Monitoring Drainage Solution Concentrations and Solute Flux in Unsaturated Soil with a Porous Cup Sampler and Soil Moisture Sensors

Soil solution samples are often collected and analyzed without consideration for either the drainage period or changes in solution or solute flux. A sampling method to assess the vertical flux of solution and solute in the unsaturated zone was evaluated. Potassium bromide (KBr) solution and distilled water were applied to the surface of a soil. Estimated and measured solution and solute discharge through the soil column were compared. The column consisted of Plainfield sand (mixed, mesic, Typic Udipsamments) packed in a 208-liter cylinder. Following solution application, discrete samples were collected at one- to two-hour intervals with a ceramic soil solution sampler centrally located in the column. In each test, the Br concentrations of discrete samples were measured, and the Br concentration of a time-integrated composite sample was calculated. Solution flux was estimated by monitoring vertical soil-water tension and content gradients with tensiometers and time domain reflectometry probes, respectively, and applying the unsaturated form of Darcy's equation. In three of four tests, differences between measured and estimated solution discharge were 20%. Differences in measured and estimated Br mass discharge ranged from 1 to 37%. Correlation coefficients between estimated and measured Br mass discharge based on discrete and composite sample concentrations were 0.905 (p = 0.095) and 0.70 (p = 0.30), respectively.

The vapour pressures of saturated aqueous solutions of potassium bromide, ammonium sulfate, copper(II) sulfate, iron(II) sulfate, and manganese(II) dichloride, at temperatures from 283 K to 308 K

Vapour pressures of saturated aqueous of KBr, (NH4)2SO4, CuSO4, FeSO4, and MnCl2 were measured in the 283 K to 308 K temperature range using an evaporimetric technique and were compared with the literature values. From the vapour pressures, the water activities, osmotic coefficients, and molar enthalpies of vaporization and solution at saturation were evaluated.

Scanning Electrochemical Microscopy of Precursor Sites for Pitting Corrosion on Titanium

Scanning electrochemical microscopy, SECM, of oxide‐covered titanium foils (∼50 Å oxide thickness) immersed in potassium bromide solutions is reported. Electrogeneration of bromine at the film is shown to occur rapidly at a few microscopic surface sites. The regions of intense faradaic activity observed in SECM images correlate directly with the location of pit nucleation. The direct correspondence between sites of faradaic activity and oxide breakdown provides a means of identifying precursor sites for pit formation.

Rheo-optical investigations on the effect of pentanol on the structure of entangled cetyltrimethylammonium bromide micelles

The effect of pentanol on the structure of entangled cetyltrimethylammonium bromide (CTAB) micelles in aqueous potassium bromide (KBr) solution has been investigated using flow birefringence and viscosity measurements. The experiments have been performed at constant surfactant and salt concentrations but with varying amounts of pentanol in the solution. Both the zero shear rate viscosity η 0 and the flow birefringence Δ n were found to increase when small amounts of pentanol were added to the solution up to a certain maximum value. This result can be explained by an initial increase in the size of the aggregates which are swollen by the alcohol. Further addition of alcohol beyond the maximum value leads to the breaking of these aggregates. This effect is illustrated by a large decrease in the two parameters cited above. In addition, the invariability of the extinction angle χ and the appearance of Newtonian behaviour in a wide range of shear, at the highest alcohol concentration, suggest the presence of less elongated particles in the solution. These data were interpreted in terms of a decrease in the curvature of the micellar surface and in the relaxation time derived from a study of the change in the extinction angle χ in relation to the structure of the entangled network.

Redox equilibria in the In(III)-In(I)-In system in aqueous KBr solutions, I. Potentiometric and coulometric study

The reproportionation of In(I) ions in acidic potassium bromide solutions was studied by means of the coulometric and potentiometric method. The formal potentials of the In(III)/In(I), In(III)/In and In(I)/In redox couples as well as the equilibrium constants of the reaction In(III)+2 In=3 In(I) were determined at a background electrolyte concentration ranging from 1 to 4 mol dm−3. Based on the experimental results, a scheme of the reproportionation reaction was proposed with regard to the participation of bromide ions. In addition, the diffusion coefficient of In(I) ions was determined using the chronopotentiometric technique.