Sodium Chloride Brine Research Articles

DMFC with Hydrogen Peroxide Cogeneration

The process of generation in the direct methanol fuel cell (DMFC) composed of the “Black Pearls 2000” gas-diffusion cathode, washed by sodium chloride brine or sea water for electroreduction and the half-membrane-electrode assembly with the Nafion 115 cation-exchange membrane, hot-pressed on one side with the carbonaceous gas-diffusion anode impregnated by Pt/Ru catalyst for methanol oxidation, has been developed. The effect of NaCl concentration in the catholyte, methanol and the KOH concentration in the anolyte, electrolyte temperature, and circulation flow rate on the generated cell voltage, current, and current efficiency have been studied in 2 h trials. An 87–95% current efficiency for generation with a rate and at current density was achieved in the DMFC with 1 M KOH in the anolyte and NaCl in the catholyte.

Temporal Variability in the Quality of Produced Water from Wells Tapping the Ozark Aquifer of Southeast Kansas

State and local agencies have become concerned that the available water supply from the Ozark aquifer in the Tri-state region of southeast Kansas, southwest Missouri, and northeastern Oklahoma may become unusable or require additional water treatment because of deteriorating quality resulting from overdevelopment. Many southwest Missouri and southeast Kansas water supplies withdraw water from a 30-60-mi (48-96-km)-wide transition zone in the Ozark aquifer that separates calcium, magnesium-bicarbonate ground water with low dissolved solids to the east from sodium-chloride brines to the west. Water-quality deterioration within the transition zone could potentially come about as a result of eastward migration or upward movement from deeper horizons of saline water. This study assessed variability in the quality of water produced from wells within the transition zone in southeast Kansas across a variety of time scales. Water samples were collected monthly from nine wells located in the transition zone over a two-year period and frequently during two 50+ hr chemical-quality pumping tests of Pittsburg well 8. The samples were analyzed for conductance and pH, and all major and selected minor dissolved inorganic constituents. Mixing curves of chloride versus bicarbonate/chloride ratio and chloride versus sodium/chloride ratio demonstrate that the produced water from Ozark aquifer wells is a mixture of low dissolved solids, calcium, magnesium-bicarbonate ground waters and sodium-chloride brines. Produced water from wells tapping sources in the Ozark and the overlying Springfield Plateau aquifers is a blend of waters from these sources, although the data suggest that the contribution from the Springfield is small relative to the Ozark aquifer. Fluctuations in the quality of the produced water during pumping most likely result from complex mixing of waters of differing quality from different parts of the Ozark aquifer within the well bore. This is borne out by bicarbonate/chloride ratio versus chloride concentration mixing curves and the dissolved constituent ratios indicative of bicarbonate and sodium in excess of that required to balance calcium + magnesium and chloride, respectively. Comparison of the 1979-1980 data with the 2006-08 data from this project indicates that the chloride concentration in some of the sampled supplies has increased. Based on extrapolation of the maximum estimated rate of chloride concentration increase, the earliest that water from Pittsburg wells 8 and 10 would exceed the recommended drinking water limit for chloride is estimated to be by the years 2045 and 2060, respectively, assuming continuation of the present rates of pumping.

Generation of Hydrogen Peroxide in DMFC

The novel process of H2O2 generation in the direct methanol fuel cell (DMFC) composed from the "Black Pearls 2000" gas-diffusion cathode (GDE), washed by sodium chloride brine or sea water for O2 electro-reduction and the half-membrane-electrode assembly (MEA) with the Nafion 115® cation-exchange membrane (CEM), hot pressed on one side with the carbonic gas-diffusion anode impregnated by Pt/Ru catalyst for methanol oxidation, has been developed. The effect of NaCl concentration in the catholyte, methanol and the KOH concentration in the anolyte, electrolyte temperature and circulation flow rate on the generated cell voltage, current and H2O2 current efficiency have been studied in 2 hour trials. 87-95 % current efficiency for H2O2 generation with a 5.286 -9.44 mg h-1 cm-2 rate and at 15 mA cm-2 current density was achieved in the DMFC with 1 M CH3OH +7M KOH in the anolyte and 30 g L-1 NaCl in the catholyte.

Concentrated sodium chloride brine solutions as an additional treatment for preventing the introduction of nonindigenous species in the ballast tanks of ships declaring no ballast on board

Currently, seawater flushing is the only management strategy for reducing the number of viable organisms in residual sediments and water of ballast tanks of vessels declaring no ballast on board (NOBOB) that traffic ports of the eastern United States. Previously, we identified several species of freshwater and brackish-water peracarid crustaceans able to survive the osmotic shock that occurs during open-ocean ballast water exchange and, potentially, to disperse over long distances via ballasted ships and NOBOB vessels. We tested the efficacy of concentrated sodium chloride brine solutions as an additional treatment for eradicating the halotolerant taxa often present in the ballast tanks of NOBOB ships. The lowest brine treatments (30 ppt for 1 h) caused 100% mortality in several species of cladocerans and copepods collected from oligohaline habitats. Several brackish-water peracarid crustaceans, however, including some that can survive in freshwater as well, required higher brine concentrations and longer exposure durations (45-60 ppt for 3-24 h). The most resilient animals were widely introduced peracarid crustaceans that generally prefer mesohaline habitats but do not tolerate freshwater (required brine treatments of 60-110 ppt for 3-24 h). Brine treatments (30 ppt) also required less time to cause 100% mortality for eight taxa compared with treatments using 34 ppt seawater. Based on these experiments and published data, we present treatment strategies for the ballast tank biota often associated with NOBOB vessels entering the Great Lakes region. We estimate the lethal dosage of brine for 95% of the species in our experiments to be 110 ppt (95% confidence interval, 85-192 ppt) when the exposure time is 1 h and 60 ppt (95% confidence interval, 48-98 ppt) when the exposure duration is 6 h or longer.

Application of an ultrasonic assisted curing technique for improving the diffusion of sodium chloride in porcine meat

Pork loins ( Longissimus dorsi) were immersed in sodium chloride brine (40 g L −1) and treated at 5 °C with one of the three following brining treatments: (1) static brining, (2) vacuum tumbling, or (3) ultrasonic brining at low-frequency (20 kHz) and low-intensity (2–4 W cm −2). The effect of ultrasonic and tumbling assisted curing technology on porcine tissue microstructure, protein denaturation, water-binding capacity (WBC), water-holding capacity (WHC), sodium chloride diffusion coefficient ( D) and on meat textural profile (TPA) was investigated. Results showed that both ultrasonic treatment and tumbling caused favourable microstructural changes in meat tissue. Water-holding capacity and textural properties were improved by ultrasonic treatment compared to both tumbled and static brined samples. However, these positive effects were highly dependent on ultrasonic intensity. Higher intensities and/or longer treatment times caused denaturation of proteins. The constant diffusion coefficient model was able to describe precisely the NaCl diffusion kinetics during brining. Ultrasonic treatment significantly enhanced the diffusion of salt compared to samples brined under static conditions and diffusion coefficient exponentially increased with increased ultrasonic intensity.

Operational Data From the World's First SAGD Facilities Using Evaporators to Treat Produced Water for Boiler Feedwater

Abstract Many new Steam-Assisted Gravity Drainage (SAGD) heavy oil recovery facilities have recently shifted from the use of warm or hot lime softening, filtration and weak acid cation (WAC) ion exchange to pretreat de-oiled produced water to an approach using falling film, mechanical vapour recompression evaporation to produce steam generator feedwater. This method of SAGD-produced water treatment is much simpler to operate, is more cost effective and results in significant increases in equipment reliability, on-stream availability and, ultimately, oil production. There are currently about 14 such evaporators operating, under construction, or in various stages of delivery in Alberta and overseas. Several of these evaporators produce feedwater for standard drum-type boilers rather than the traditional Once-Through Steam Generators (OTSG) due to the high level of water purity obtainable with the evaporative approach. This paper provides data from operational facilities, including evaporator distillate quality, heat transfer information, fouling rates, cleaning frequencies, energy and chemical consumption, and other technical and operational data. In conjunction with this evaporative produced water treatment process, some facilities have taken the additional step of recovering all liquid waste streams for re-use in the plant, resulting in zero liquid discharge (ZLD). Designing the facility for ZLD eliminates the need for deep well injection, minimizes make-up water requirements and simplifies the permitting process. Introduction The recovery of heavy oil from oil sands formations requires large volumes of water; sometimes three times the amount of water compared to the oil recovered. In steam-assisted gravity drainage (SAGD) facilities, 100% quality steam is injected into the well to heat up the formation and get the heavy oil to flow. Oil and condensed steam are brought to the surface where the oil is separated and the condensate, or produced water, is treated and recycled to produce the steam. This huge water demand and ultimate conversion to steam requires the maximum amount of recycle potential from the water. Produced water derived from oil recovery processes (SAGD and non-SAGD) can be characterized as predominantly sodium chloride brine with high silica and minimal amounts of hardness. High alkalinity is present as well. Overall concentration of the water can range from about 1,000 mg per litre TDS to over 10,000 mg per litre, and there is always some amount of organic material present. The method of converting this water to boiler feedwater must be carefully evaluated, both technically and economically. This paper discusses an evaporative method of deriving high quality boiler feedwater from produced water. A comparison is made to the 'traditional' method of warm (or hot) lime softening combined with weak acid cation exchange (WLS/WAC). A complete evaluation of these two approaches must also include the steam generation equipment. Having high quality boiler feedwater, as derived from an evaporative process, allows the use of drum boilers in lieu of once-through steam generators (OTSG). Since the WLS/WAC system does not produce a high quality water, OTSG must be used as these boilers are more tolerant of poorer quality feedwater.

Ultrasonic degradation of metal complexes with organic substances present in mineralized water, brines, and sodium chloride solutions

The applicability of ultrasound over a frequency range from 18 kHz to 2 MHz to the degradation of metal complexes with organic compounds present in water, brines, and sodium chloride solutions was studied. It was found that ultrasound over a frequency range from 18 to 100 or 200 kHz can be used for the degradation of complexes in sodium chloride solutions and brines or seawater, respectively. In this case, the best results were obtained over the frequency range 80–100 or 80–200 kHz, respectively.

Prediction of Strontium Sulfate Scale Formation in Oilfield Environment

Abstract An easy and reliable method for predicting a scale tendency of strontium sulfate as a function of several variables including sodium chloride brine composition, temperature, and pressure effect is developed. The effect of the amount of sulfate tied up as [MgSO40] on SrSO4 solubility is also considered. The magnesium sulfate dissociation constants and strontium sulfate experimental solubility data is fitted in mathematical equations. These equations can be easily used to determine SrSO4 scaling tendency in environments common to oil field brines. The reliability and key features of the prediction method are illustrated in the text with oilfield well cases. Results obtained using the present model are in good agreement with field observation. The method presented in this study is easy to use, reliable, and can be applied to any producing wells where SrSO4 occurs.

Localized Corrosion of Alloy 22 in Sodium Chloride Solutions at Elevated Temperature

Abstract The localized corrosion behavior of Alloy 22 (UNS N06022) in acidified (pH = 3) sodium chloride (NaCl) brines at elevated temperature (80°C) and under potentiostatic and open-circuit condi...

Split-precipitation — An ecological alternative in the purification of crude sodium chloride brine

Due to the impurities of rock salt, crude sodium chloride brine requires purification. Only purified brine is capable to be used in modern evaporators or for the production of soda ash in a Solvay process. The brine purification process causes the onset of solid precipitates in the form of sludge. If this mud cannot be made use of in any way, it is washed into waters where it covers the ground and accumulates over years and decades. A novel brine purification process, Split-Precipitation, helps significantly reduce the amount of solids in the sludge (by about 30 wt%). The principal idea of Split-Precipitation is to initially precipitate Ca2+ and Mg2+ ions using soda ash and to work up the carbonates at the end with gypsum. This process does not require many additional expenses, but combines several ecological advantages.

Use of Evaporation for Heavy Oil Produced Water Treatment

Abstract Heavy oil recovery processes have traditionally used "once through" steam generators (OTSG) to produce high pressure steam for injection into geological formations containing heavy oil. The heat given up by the condensing steam fluidizes the heavy oil and allows the oil/water mixture to be brought to the surface. The oil is recovered as product and the water, referred to as produced water, is de-oiled and treated for feedwater to the OTSG. The typical treatment method for produced water is warm or hot lime softening (WLS or HLS), filtration, and weak acid cation exchange (WAC). An alternative method of produced water treatment is vertical tube, falling film, vapour compression evaporation. This method:eliminates physical-chemical produced water treatment;results in lower life cycle costs;does not produce any softener sludge for disposal;minimizes the number and volume of waste streams requiring disposal;requires fewer maintenance materials and less maintenance labour;reduces the required amount of produced water de-oiling equipment;dramatically increases OTSG feed water quality, improving OTSG reliability; and,provides increased system availability and reliability. For steam assisted gravity drainage (SAGD) processes, which require 100% quality steam, it has the added advantage of producing water of sufficient quality for use in standard packaged boilers in lieu of OTSG. Packaged boilers are less expensive than OTSG, produce a much smaller liquid blowdown stream, and result in a boiler feed system which is 20% smaller than that of an OTSG. Introduction Heavy oil recovery requires large volumes of water commensurate in volume to the production of oil that it yields. Water is used in the form of steam to heat the geological formations that hold the oil. The oil is fluidized by the condensing steam and the oil/water mixture is pumped to the surface. The oil and water are separated. The oil is recovered as product and the water, referred to as produced water, is de-oiled and treated for reuse in the steam generator. Traditionally, "once-through" steam generators (OTSG) have been used to produce 80% quality steam (80% vapour, 20% liquid) for injection into the well. A relatively new heavy oil recovery process, steam assisted gravity drainage (SAGD), requires 100% quality steam to be injected into the well (i.e., no liquid water). To produce 100% quality steam using OTSG, a series of vapour-liquid separators are required to separate the liquid water from the steam. The 100% quality steam is then injected into the well. For both SAGD and non-SAGD applications, the produced water can generally be characterized as predominantly sodium chloride brine with high silica and minimal calcium and magnesium. High alkalinity, or carbonate, is present as well. The produced water generally contains about 4,000 mg/l total dissolved solids but can be much higher depending on the geological contribution. Dissolved and emulsified organics (oil) are present at a variety of levels, depending on the oil separation processes used.

Combined effect of alkali pretreatment and sodium chloride addition on the olive fermentation process

Green olives of the Tunisian variety “Meski” were treated according to a Spanish-style green olive preservation process by using an alkaline treatment (1.5, 2 and 2.5% (w/v) NaOH) to eliminate bitterness, combined with different brine concentrations (6, 9 and 12% (w/v) NaCl). A spontaneous fermentation by the environmental microflora took place. Results showed that 2% NaOH solution and 9% sodium chloride brine was an optimal combination inducing the best growth of Lactobacillus species (10 8 CFU/ml) and acidity of 0.726 g lactic acid/100 ml brine. In all trials and independently of the treatment, Lb. plantarum was the most dominant strain of Lactobacillus. Moreover, pretreatment with lye and lactic fermentation of olives contributed to coliform elimination.

Estimating Density, Formation Volume Factor, Compressibility, Methane Solubility, and Viscosity for Oilfield Brines at Temperatures From 0 to 275 ° C, Pressures to 200 MPa, and Salinities to 5.7 mole/kg

Abstract New correlations for density of methane-free sodium chloride brine and solubility of methane in sodium chloride brines, valid over wide ranges of pressure, temperature, and salinity, are presented. Both correlations agree with the best available measurements within experimental error over most of the range of validity. These new correlations are combined with published correlations for methane partial molar volume to provide accurate and internally consistent estimates of brine density, specific volume, formation volume factor, and coefficient of isothermal compressibility at pressures above or below the bubble point pressure. The brine density correlation is valid for temperatures from 0 to 275 ° C (32 to 527 ° F), pressures from 0.1 to 200 MPa (14.5 to 29,000 psi), and sodium chloride content from 0 to 6 moles/kg H2O (0 to 26﹪ by weight). The methane solubility correlation is valid for temperatures from 20 to 360 ° C (68 to 680 ° F), pressures from 0.9 to 200 MPa (130 to 29,000 psi), and sodium chloride content from 0 to 6 moles/kg H2O (0 to 26﹪ by weight). A modification of an existing correlation for brine viscosity is also presented, extending its range of applicability to temperatures between 20 and 300 ° C (68 to 572 ° F), pressures between 0.1 and 200 MPa, and salinity between 0 and 5.4 moles NaCl/kgH2O (0 to 25﹪ NaCl by weight). Introduction Oil companies today produce in excess of 33 million cubic metres of water per day (210 MMbbl/day). The associated cost of handling this water production is estimated to exceed $40 billion per year(1). Understanding and dealing with these costs requires accurate knowledge of the water properties. Properties such as density, viscosity, and solubility affect the volume and movement of water through the reservoir, in the well bore, and at the surface facilities. As water production continues to increase, so does the importance of our understanding of the properties of the produced water. Many experimental studies of the behaviour of systems comprising water, sodium chloride, and methane have been reported in the physical chemistry literature during the last 25 years. By and large, the results of these studies have not been widely disseminated within the petroleum engineering community. In this paper, we present new correlations based on the published data for estimating those properties of primary interest to the petroleum engineer, namely the density, specific volume, methane solubility, formation volume factor, coefficient of isothermal compressibility, and viscosity. The next two sections of the paper discuss the development of the new brine density and methane solubility correlations. The third section shows how the brine density and methane solubility correlations may be combined with previous work to calculate internally consistent values for reservoir brine density, specific volume, coefficient of isothermal compressibility, and solution gas-water ratio at pressures above or below the bubble point pressure. The final section presents a modification of a published brine viscosity correlation, extending its range of applicability to temperatures of 300 ° C (572 ° F) and pressures of 200 MPa (29,000 psi).

Simultaneous Conductivity and Viscosity Measurements as a Technique To Track Emulsion Inversion by the Phase-Inversion-Temperature Method

Two kinds of transitions can occur when an emulsified water-oil-ethoxylated nonionic surfactant system is cooled under constant stirring. At a water-oil ratio close to unity, a transitional inversion takes place from a water-in-oil (W/O) to an oil-in-water (O/W) morphology according to the so-called phase-inversion-temperature method. At a high water content, a multiple w/O/W emulsion changes to a simple O/W emulsion. The continuous monitoring of both the emulsion conductivity and viscosity allows the identification of several phenomena that take place during the temperature decrease. In all cases, a viscosity maximum is found on each side of the three-phase behavior temperature interval and correlates with the attainment of extremely fine emulsions, where the best compromise between a low-tension and a not-too-unstable emulsion is reached. The studied system contains Polysorbate 85, a light alkane cut oil, and a sodium chloride brine. All transitions are interpreted in the framework of the formulation-composition bidimensional map.

Prediction of Brine Application for Pretreatment and Anti-Icing

Highway anti-icing strives to prevent the ice—pavement bond by pre-application of chemicals. An effective anti-icing program requires prediction and estimation of the amount, type, and timing of chemicals needed for the expected precipitation event while compensating for time and traffic decay of the chemical on the highway surface. Development of a sodium chloride brine anti-icing methodology was accomplished with an extensive study of brine residual decay on four pavement types. In October and November 2002, brine residual was monitored for up to 3 days after initial application on five sections of four-lane divided highways in Ohio. Four evenly spaced test stations within each highway section were monitored for residual as time passed and traffic accumulated. An instrument that dissolves salt and measures conductivity was used to measure available salt residual. Efficacy of the brine to prevent ice—surface bonding was estimated by using freeze—thaw cycles of various brines. After freezing, the bonds were held vertically as temperature was raised. The appearance of liquid below the interface indicated release. Field and laboratory data were correlated to estimate freezing temperatures for various salt residuals as a function of brine dilution represented by precipitation in depth of rainfall. Results support estimation of brine application requirements for three specific pavements based on expected precipitation and the salt residual models developed in the study. A set of graphs is included to implement the algorithm.

Virioplankton community structure along a salinity gradient in a solar saltern.

The virioplankton community structure along a salinity gradient from near seawater (40 per thousand ) to saturated sodium chloride brine (370 per thousand ) in a solar saltern was investigated by pulsed-field gel electrophoresis. Viral populations with genome sizes varying from 10 kb to 533 kb were detected. The viral community structure changed along the salinity gradient. Cluster analysis of the viral genome-banding pattern resulted in two main clusters. The virioplankton diversity within the samples with salinity from 40 per thousand to 150 per thousand was on the same cluster of a cladogram. The other group consisted of virioplankton from samples with salinity above 220 per thousand. The virioplankton diversity in the different samples was calculated using the Shannon index. The diversity index demonstrated an increase in diversity in the samples along the gradient from 40 per thousand to 150 per thousand salinity, followed by a decrease in the diversity index along the rest of the salinity gradient. These results demonstrate how viral diversity changes from habitats that are considered one of the most common (seawater) to habitats that are extreme in salt concentrations (saturated sodium brine). The diversity index was highest in the environments that lie in between the most extreme and the most common.

The Merksplas-Beerse geothermal well (17W265) and the Dinantian reservoir

The Merksplas-Beerse well (North Belgium) is a low-enthalpy geothermal production well targeting the Dinantian karstic limestones to a total depth of 1761 m. The presence of methane gas in these limestones generated a particular interest in this well. This paper describes the geological profile of this well and the Dinantian reservoir. The Namurian-Visean boundary at 1630 m is determined by the base of the dipmeter draping pattern in the radioactive Chokier shales (base of the Namurian) on top of the karstified Dinantian limestone. The stratigraphic composition of the transitional interval from Dinantian to Silesian correlates closely to the nearby Turnhout well. The two fractured intervals at 1630-1656 and 1739-1747 m respectively were identified in the Dinantian limestones. They are associated with siliciclastic sections in between pure limestones. The reservoir water is a sodium chloride brine of about 74 °C and at a pressure below the hydrostatic. The water is slightly radioactive because of the contact with the Chokier hot shales. A carbon dioxide gas with methane and nitrogen admixture is dissolved in the water. The gas liquid ratio at standard conditions is about one and the bubble point is around 200-400 psi at reservoir temperature. A long duration pumping test shows a high fracture permeability and a productivity index of 5.4 m3/h/bar with a productivity to injectivity ratio of 1.45.

Cooked and brined shrimps packed in a modified atmosphere have a shelf‐life of >7 months at 0 °C, but spoil in 4–6 days at 25 °C

Summary Spoilage and safety of cooked, brined and modified atmosphere packed shrimps were studied at 0, 5, 8, 15 and 25 °C. Shrimps from two sources, cold and warm waters, were brined in a sodium–chloride brine containing benzoic, citric and sorbic acids. Shelf‐life was above 7 months at 0 °C but only 4–6 days at 25 °C. Apparent activation energy for the effect of temperature on shelf‐life was > 100 kJ mol‐1. This pronounced effect of temperature was explained by changes in spoilage microflora at different storage temperatures. Simple and empirical mathematical models for rates of spoilage were developed for the prediction of shelf‐life at different temperatures. To evaluate safety, products were challenged with Listeria monocytogenes and spores of Clostridium botulinum. Above 5 °C growth responses of L. monocytogenes followed the square root model with a Tmin‐value of +0.2 °C. Cl. botulinum produced toxin at the time of spoilage at 25 °C but only in shrimps with < 3% water‐phase salt.

Direct osmotic concentration of tomato juice in tubular membrane – module configuration. II. The effect of using clarified tomato juice on the process performance

A study was carried out by using a new tubular direct osmosis module, constructed by PCI UK and equipped with a novel AFC99 membrane 400 μm thick, to investigate the effect of clarifying tomato juice on the rate of direct osmotic concentration. Under virtually the same operating conditions five respective clarifications of juice were tried including full, unclarified, tomato juice. The process performance was calculated in terms of permeation flux. In all the experimental runs the osmotic medium was sodium chloride brine (initial concentration approx. 23% NaCl). A remarkable increase of permeation flux (over 100%) was observed shifting from unclarified to the clarified tomato juice. Clarification was carried out by passing the juice through 35 μm mesh and also by using membranes of molecular weight cut-off 200 000, 100 000 and 25 000 Daltons (Da), respectively, in order to obtain the juice ultrafiltrates. It is also worth mentioning that the flux value obtained with 25 000 Daltons (Da) ultrafiltrate appeared to be considerably higher than values reported in experiments carried out by other researchers, where unclarified juice was used, despite the disadvantage of a far thicker membrane being used in the present investigation. This specific finding discloses great potential in using a combined low temperature and pressure ultrafiltration and direct osmosis process to produce tomato concentrates.

Chromatographic determination of anions in industrial salt and sodium chloride brines used in chlor–alkali industry

An ion chromatographic method using an ion-exchange column for the simultaneous analysis of sulphate and chlorate in industrial salt and sodium chloride brines has been developed. A mixed eluent of 2.0 m M sodium carbonate and 0.75 m M sodium bicarbonate is used. The effects of various parameters have been reported and critically discussed. The results are precise and afford simultaneous determinations of sulphate and chlorate.