The determination of sulphate in fertilizers by atomic absorption spectrometry

Methods are described for the determination of sulphate in superphosphate fertilizers. Barium sulphate precipitated from an acidified EDTA solution is filtered onto a membrane filter and redissolved in ammoniacal EDTA, and the barium equivalent to the sulphate is determined by atomic absorption spectrometry. Alternatively, after precipitation of calcium as oxalate during sample solution preparation, and by following a similar sulphate precipitation technique, excess of barium is determined in the filtrate. No interferences were encountered when a nitrous oxide—acetylene flame was used with a potassium ionization buffer.     

Determination of barium in sulphide ores, concentrates and other geological samples by flame atomic-absorption spectrometry

A rapid, precise and selective analytical method has been developed for estimation of barium in geological samples by flame atomic-absorption spectrometry. The method consists of precipitation of barium sulphate with ammonium sulphate, followed by dissolution of the sulphates in EDTA at pH 10. The barium in this solution is measured by AAS with a nitrous oxide-acetylene flame. Appreciable amounts of lead, calcium and strontium can be tolerated in the method, which has been applied for estimation of barium in sulphide ores and concentrates of lead, zinc and copper, and is feasible for estimation of barium from 20.0 ppm to the per cent level in such geological samples.     

Surface modified aluminium hydroxide in flame retarded noise damping sheets

Flame retarded polyethylene compounds were prepared using a series of aluminium hydroxide of different particle size applying a milling processes and special precipitation technologies. The processability and flame retardant efficiency of the flame retarded systems were compared. The effects of various surface modifications were analysed in case of one selected type of aluminium hydroxide. A silicone terminated reactive surfactant promoted not only the processability but also the flame retardant efficiency. Noise damping sheets were prepared by simultaneous application of aluminium hydroxide and barium sulphate in an elastomer blend matrix. V0 flame retardant grade could be achieved this way accompanied with improvement in the acoustic properties and maintenance of the mechanical properties.     

Separation and determination of trace amounts of barium as its thenoyltrifluoroacetone complex with dibenzo-18-crown-6 by means of synergistic extraction and flame photometry

Summary A new method for the separation and determination of trace amounts of barium at the ppb-ppm level in water as its thenoyltrifluoroacetone (TTA) complex with dibenzo-18-crown-6 (DB18C6) comprises synergistic extraction and back extraction combined with flame photometry. The effect of various factors (solvent, size of crown ether, reagent concentration, shaking time, preconcentration factor, foreign ions etc.) on the extraction and back extraction of barium has been investigated. The barium TTA chelate in o-dichlorobenzene forms stable adducts with DB18C6 [Ba(TTA)₂ · nDB18C6, n=12]; the stability constants (n) of the adducts determined by means of the curve fitting method are log ₁=3.77 and log ₂=7.91. The content of barium in sodium chloride and sodium nitrate of guaranteed reagent grade was found to be 9.67±0.08 g/g and 7.86±0.09 g/g, respectively.     

Preparation and Properties of Nb-Coated Barium Titanate Composite Particles by Surface Modification with Nb Alkoxide in Hydrophobic Solvent

Chemical processing for the preparation of Nb-coated barium titanate composite particles was investigated using surface modification technology, hydrolyzing Nb ethoxide on the surface of barium titanate particles dispersed in hydrophobic solvent.It was confirmed from the measurements of specific surface area and zeta potential as well as SEM, TEM and EDX observations of the resulting composite particles that the original barium titanate particles were coated uniformly with hydrolysis product of Nb ethoxide.Barium titanates coated with 1 wt% of Nb as oxide were well sintered at 1200–1300°C. The dielectric constants of the sintered barium titanates showed flattened temperature dependence, but it depended upon the average particle size of original barium titanate. The sintered bodies of Nb-coated barium titanate powders with average particle size of 0.2 m gave dielectric constants of 2000–3000 and those of barium titanate with average particle size of 0.5 m showed dielectric constants of 3000–4000 at room temperature.The microstructure of the sintered barium titanate coated with Nb oxide consisted of grains of about 1 m, smaller than those of sintered original barium titanate.     

Determination of sulphide ion at trace levels by ethylation and gas chromatography

Summary A method is described for the determination of sulphide ion in aqueous samples by gas chromatography. Sulphide is ethylated with diethyl sulphate and the resulting diethyl sulphide is extracted with chloroform and determined with a gas chromatograph equipped with a flame ionization or a flame photometric detector. In the case of a flame photometric detector, the detection limit for sulphide ion is 0.05 g/ml. Other anions commonly found with sulphide ion do not interfere. Sulphide ion in spring waters was analysed by this new method and for comparison also by colorimetry (methylene blue). The results revealed the reliability of the new method.

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Bestimmung von Sulfidspuren durch Ethylierung und Gas-Chromatographie

Zusammenfassung Sulfid wird mit Diethylsulfat ethyliert, das gebildete Diethylsulfid mit Chloroform extrahiert und gaschromatographisch mit Hilfe eines Flammenionisationsoder eines flammenphotometrischen Detektors bestimmt. Die Nachweisgrenze beträgt 0,05 g S/ml für den FPD. Anionen, die üblicherweise mit Sulfid zusammen vorkommen, stören nicht. Das Verfahren wurde, im Vergleich mit der colorimetrischen Methylenblaumethode, auf Quellwasser angewendet. Es wurde gute Übereinstimmung der Ergebnisse erzielt.

     

Separation of Ra and Th from rock matrices for alpha-spectrometry

Dating rocks using²²⁶Ra/²³⁰Th isochrons demands radiochemical purification of radium and thorium. This paper presents an improved method. Rocks are solubilised by nitric/nydrofluoric digestion followed by dissolution of insoluble fluorides by boric/nitric acids, and Th is extracted by passing the 8M nitric solution through an anion column in nitrate form. The eluant contains Ra and Ba which are precipitated as sulphate and redissolved in alkaline EDTA. Complete separation of Ba and Ra from sulphate is on an AG 1×8 anion column in EDTA form, which was found better than the chloride form. The Ba+Ra is separated on an AG 50W×8 cation column, and uses CDTA as an eluant for Ba. Careful pH control is essential. Ra elutes later with EDTA or 4M HCl and is precipitated with 125 g barium as sulphate to yield a source suitable for -spectrometry, or further treated to electroplate the Ra. The yield tracers used are²²⁸Th and²²⁴Ra. Because the sample contains natural²²⁴Ra a correction must be applied, calculated from the amount of natural²³²Th in the Th spectrum. Th may be precipitated with 100 g of ferric iron and gives a spectrometry-quality source, but further purification and electrodeposition was found to be preferable. Variations on the method for the case of analysis of calcium-rich fish otoliths are described.     

Determination of traces of uranium in tungsten and molybdenum by radiochemical neutron activation analysis via the fission product140Ba

A radiochemical separation procedure has been developed to determine traces of uranium in tungsten and molybdenum. In this procedure the fission product¹⁴⁰Ba, as indicator nuclide for uranium, is selectively separated from the matrix activities and from all other long-lived activation and fission products and obtained at high purity. The radionuclide in the final fraction is sufficiently pure so that it can be measured with high counting efficiency by -counting. The separation procedure consists of two steps: a cation-exchange separation to separate barium from the anionic matrix tungste or molybdate, and many other elements. In the second step the Ba-fraction is further purified by precipitation of barium as barium chloride in 8M hydrochloric acid. The precipitate is then dissolved in water for -counting via the Cerenkov effect. The chemical yield for barium is 94.6±2.6%. When samples of 0.1 g, a thermal neutron flux of 2·10¹³ n·cm^–2·s^–1, an irradiation time of 10 hours and a measuring time of 2 hours were applied, then the detection limit of uranium was 4 ng/g.Presented at the 3rd Intern. Conf. on Nuclear and Radiochemistry, Vienna, September 7–11, 1992.     

Rapid method for the spectrophotometric determination of sulphate in surface water using ion-exchange separation and the sulphate and chlorophosphonazo III (CPA III)-Ba2+ complex reaction

Summary A rapid spectrophotometric method for the determination of SO ₄ ^2– in surface water is reported. It is based on the reaction of CPA III-Ba²⁺ complex with SO ₄ ^2– in acidic medium in the presence of ethanol. Beer's law is obeyed up to 120 g of SO ₄ ^2– in 25 ml solution. The molar absorptivity is 6.3×10³ l · mol^–1 · cm^–1 at 500 nm, and the coefficient of variation varies from 1.85% to 3.10%. The absorbance remains stable for at least 24 h and interfering ions are separated by strongly acidic cation-exchange resin.Among the methods for determining micro amounts of sulphate in water, the following can be mentioned: An indirect method using a suspension of barium chloranilate [1–3] or barium chromate [4–6] and the classical turbidimetric (BaSO₄) method [7, 8]. It is well known that the latter is more convenient, but of rather low precision and sensitivity. The formers are tedious and time-consuming, because they require to separate the precipitation of BaSO₄.In 1985, we have used CPA III for the indirect spectrophotometric determination of sulphate in soils, but the procedure is not fast [9]. It is the purpose of this work to propose a more convenient method for the spectrophotometric determination of sulphate in water.

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Schnelle spektralphotometrische Sulfatbestimmung in OberflÄchenwasser aufgrund von Ionenaustausch und der Reaktion von Sulfat mit dem Chlorophosphonazo(III)-Ba-Komplex

     

The determination of sulphate by the ring oven technique and its application to air pollution measurement

Summary The ring oven technique ofWeisz is used for the estimation of sulphate, using the coloration of barium sulphate by co-precipitated permanganate. This method is applied to the determination of the air pollutants sulphur dioxide and sulphate.The limit of identification is about 0.1g, the accuracy about 25%.

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Zusammenfassung Die Ringofenmethodik vonWeisz wurde für die Bestimmung von Sulfat verwendet, wobei das Bariumsulfat durch Mitfällung von Permanganat gefärbt wird. Diese Methode wurde zur Bestimmung der Luftverunreinigung durch Schwefeldioxyd und Sulfat angewendet.Die Erfassungsgrenze ist ungefähr 0,1g, die Genauigkeit beträgt etwa 25%.

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Résumé On utilise la technique du four annulaire deWeisz pour l'évaluation des sulfates à l'aide de la coloration du sulfate de baryum coprécipité avec le permanganate. On applique cette méthode à la détermination des substances polluant l'air, anhydride sulfureux et sulfate. La limite d'identification est d'environ 0,1g, la précision d'environ 25%.

     

The determination of sulphate by flow-injection analysis with exploitation of pH gradients and EDTA

A modified method for the turbidimetric determination of sulphate as barium sulphate is proposed. The carrier stream is an alkaline barium—EDTA solution; the sample zone is sufficiently acidic to allow precipitation of barium sulphate. The excess of EDTA in the carrier stream ensures that residual precipitate is redissolved and the system kept clean.     

Schnelle Trennung von Barium aus einem Gemisch von Spaltprodukten

Zusammenfassung Eine Methode zur schnellen und selektiven Trennung von Barium aus einem Gemisch von Spaltprodukten wurde ausgearbeitet, die auf der Fällung des Bariumsulfats in Anwesenheit von äDTA beruht. Die Selektivität wurde durch Messung der -Spektren und der Zerfallskurven ÜberprÜft. Die Schnelligkeit der Methode wird durch die Abtrennung des Kernisomers ^137m Ba aus einem im Gleichgewicht befindlichen Gemisch von ^137m Ba und ¹³⁷Cs gezeigt.Das angefÜhrte Verfahren eignet sich fÜr die Herstellung von radiochemisch reinem Barium, fÜr die quantitative Auswertung der Kontamination der Spaltprodukte und fÜr die Berechnung des Alters radioaktiver atmosphärischer Niederschläge.

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Summary A method has been developed for the rapid and selective isolation of barium from a mixture of fission products, based on precipitating barium sulphate in EDTA medium. The selectivity was checked by measuring -spectra and by decay curve analysis. The rapidity of the method is illustrated by the isolation of the ^137mBa isomer from an equilibrium mixture of ¹³⁷Cs+^137m Ba.The method described is convenient for preparing radiochemically pure barium, for a quantitative evaluation of a decontamination with fission products and for determining the age of radioactive fall-out.

     

Co-precipitation in some binary sulphate systems

Studies have been made of the distribution behaviour of tracers with alkaline earth sulphates, using the technique of precipitation from homogeneous solution. The co-precipitation of strontium with barium sulphate and of lead, lanthanum, and yttrium, separately, with barium sulphate, and with strontium sulphate, were investigated. Although there was qualitative correlation between the observed values of the distribution coefficient and the theoretical solubility product ratios for each of the binary systems studied, the divergence between theory and observation was so great that it seems unlikely that there is any quantitative correlation.     

Trennung von anorganischen Schwefelanionen durch Ionenaustausch- und Ionenpaar-Chromatographie

Summary Ion-exchange chromatography on a AS4A-column followed by a hollow fiber suppressor is suitable for the separation of sulphite, sulphate, thiosulphate and thiocyanate. Injecting a volume of 110 l, conductivity measurement yields detection limits between 15 g/l for sulphate and 75 g/l for sulphite.Ion-pair chromatography on a LiChrospher-100CH column using tetrabutylammonium ions as lipophilic reagent additionally makes possible the determination of dithionate, peroxodisulphate and tetrathionate, thus including seven anions in one run. Using a micro membrane suppressor and conductivity detection, detection limits between 10 g/l for sulphate and 70 g/l for tetrathionate are achieved with injection of 50 l samples.

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Herrn Prof. Dr. W. Fresenius aus Anla\ seines 75. Geburtstages gewidmet     

Influence of Ba on the electrodeposition of226Ra

A detailed study of the influence of barium on the electrodeposition of²²⁶Ra was made using two different procedures. High yields (80–90%) were attained when the amounts of barium were not very significant. However, the²²⁶Ra yields fell drastically for amounts slightly greater than 0.10–0.15 mg of Ba, according to the electrodeposition procedure. Samples containing trace amounts of barium less than 100–150 g can thus be treated with no barium-radium separation being required.²¹⁰Po was also deposited, although practically no influence of barium on the Po plating was observed. The²²⁵Ra resolution rose uniformly (25 to 55 keV) as the amount of barium rose up to 1 mg. These resolutions allow one to make a direct accurate determination of²²⁶Ra as well as an indirect determination of²²⁴Ra and²²³Ra via measurement of their daughter products.     

Zur flammenphotometrischen Sulfatbestimmung

Zusammenfassung Die bekannte Bestimmungsmethode für Sulfat durch Fällung als BaSO₄ und anschließende flammenphotometrische Bestimmung von Barium wird verbessert. Bei Beachtung der Lösungseinflüsse und bei Verwendung geeigneter Vergleichslösungen ist die Bestimmung von 20–100 mg Sulfat möglich, wenn man den Niederschlag in ÄDTA-NaOH löst. Für Sulfatmengen unter 20 mg sollte ÄDTA-Triäthanolamin verwendet werden.

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Summary The determination of sulphate by precipitation as BaSO₄ and subsequent flame photometric determination of barium has been improved. Considering the influences from the solution and using suitable standard solutions the determination of 20 to 100 mg sulphate is possible by dissolution of BaSO₄ in EDTA-NaOH. For quantities of sulphate smaler than 20 mg the precipitate should be dissolved in EDTA-triethanolamine.

     

Precipitation separation of lead and calcium,strontium, barium from acidic solutions using crown ether and tungstosilicic acid

It was found that lead reacts with 18-crown-6 (L) and tungstosilicic acid (H₄A) in acidic solutions and a compound with low solubility is formed what was confirmed by radiometric titration methods. Coprecipitation of complexion cation of PbL²⁺ with similar complexion cations of calcium, strontium and barium was studied. Formation of low soluble salts was utilized for separation of Pb from Ca, Sr and Ba from 1 mol·dm^–3 HNO₃. The ratio of Pb/Ca, Pb/Sr and Pb/Ba in the precipitation or separation factors S_pb/M undoubted depends on the ratio of the stability constants of lead and metals with 18C6 (_Pb/_M), what can be used for determination of more precise constant stability _M.     

Indirect flame photometric determination of sulphate ions

In this paper the possibilities have been studied of determining sulphate ions by indirect flame photometry by difference. Barium and Strontium in constant concentration were used as background elements. By means of the methods proposed sulphate ions can be determinined in the concentration range 0 to 70 p.p.m. with barium and 0 to 110 p.p.m. with strontium. The determinations can be carried out in dilute solutions of alkali metal sulphates and sulphate ions can also be estimated in the presence of macroquantities of other compounds. This may prove useful for the quantitative estimation of sulphate as an impurity in Chemical reagents. Some examples are given of the determination of the degree of purity of substances containing sulphate as impurities.     

Sample introduction assisted by compressed air in flame furnace AAS: a simple and sensitive method for the determination of traces of toxic elements

The power of detection of flame AAS for the toxic elements Cd, Hg, Pb and Tl can be improved by 1–2 orders of magnitude by using flame furnace AAS. In flame-furnace AAS, liquid samples are introduced directly into a nickel tube located in the flame, in the simplest case through a ceramic thermospray capillary. Transportation of the samples is achieved by using compressed air only. Comparatively low detection limits are achieved by both beam injection flame furnace (BIFF-AAS) and thermospray flame furnace AAS (TS-FF-AAS). For TS-FF-AAS, a pressure of less than 20 kPa (<80 in. water) is required. The TS-FF-AAS technique is very simple, robust and cheap. The detection limits were 0.2–0.4 g L^–1 (Cd), 40–100 g L^–1 (Hg), 5–9 g L^–1 (Pb) and 4–14 g L^–1 (Tl), respectively, depending on the method, flow rate and sample volume used. Pb and Cd were found at concentrations of 0.1–2 and 0.005–0.3 g g^–1, respectively, in samples of various spices.Dedicated to the memory of Wilhelm Fresenius.     

Reversible aggregation Part I. Reversible flocculation monitored by turbidity measurements

The aggregation of four separate polystyrene latices, ranging in diameter from 210 nm to ca. 1 m, using sodium chloride and magnesium sulphate as the electrolytes, has been examined turbidimetrically. The reversibility of the aggregation was examined using a dialysis technique. It was found that for large particle size latices, diameters 781 nm and 1 m, aggregation was reversible in sodium chloride even at concentrations up to 0.5 mol dm^–3. The aggregation of smaller particles was not reversible. The aggregation of large particles in magnesium sulphate solutions was not readily reversed by dialysis. The latter result does not appear to agree with theoretical predictions.Dedicated to Professor Dr. Armin Weiss on the occasion of his 60th birthday.