Turbidimetric determination of sulphate in plant digests and natural waters by flow injection analysis with alternating streams

An improved flow injection system with alternating streams of reagents is described for the turbidimetric determination of sulphate. Samples are injected into an inert carrier stream which is mixed with barium chloride to form a barium sulphate suspension. The range of the method can be extended to low concentrations by continuously adding sulphate to the sample carrier stream. System performance is improved by automatic alternate pumping of the reagent stream and an alkaline EDTA solution at high flow rate. All operations are controlled by an electronically-operated proportional injector-commutator. Even after routine analysis of 3000 samples of natural waters and plant digests, baseline drift was not observed. The proposed method is suitable for 120 samples per hour with a relative standard deviation less than 1% for sulphate concentrations in the range 1–30 ppm (waters) or 5–200 ppm (plant digests). The results compare well with those obtained by standard manual procedures.     

Complexometric estimation of ferric iron

Summary Ferric iron has been determined alone or in presence of barium chloride, calcium chloride, magnesium sulphate, mercuric chloride, manganese sulphate, strontium nitrate, chromic sulphate or zinc sulphate by titrating it with EDTA, using potassium thiocyanate-p-anisidine indicator. In these complexometric titrations, the quantitative results obtained by using potassium thiocyanate-p-anisidinie indicator are comparable with those obtained with Bindschedler's green indicator; and the metallic salts mentioned above do not interfere in the estimation of ferric iron by this method.     

A rapid turbidimetric method for the determination of total sulphur in zinc concentrate

A rapid, simple and reliable routine method for the determination of total sulphur in zinc concentrates, roasted products and leached residues from zinc smelters is described. The method involves the fusion of the ample with sodium peroxide and sodium carbonate or routine acid decomposition and dissolution to give soluble compounds. The absorbance of the barium sulphate suspension produced by the addition of barium chloride powder to a dilute hydrochloric acid solution of the sample, containing cetyltrimethylammonium bromide solution as a dispersing agent, is measured at 420 nm. The results obtained for some zinc concentrates and other products are compared with those obtained by the conventional gravimetric barium sulphate method. Results for a reference zinc concentrate and other samples with various matrices and the results obtained with standard additions to the samples are good.     

Determination of Sulphate by Titrimetric and Colorimetric Measurement of Equivalent Displaced Zinc Ion

Abstract

Two methods are described for the determination of sulphate in the range of 200 μg to 100 mg by dissolving precipitated barium sulphate in excess of EDTA at pH 12.5. A titrimetric procedure involves back titration of excess EDTA with a standard zinc solution, while a complementary spectrophotometric method makes use of the stability of the barium EDTA complex in the presence of an excess of zinc ions; the latter are reacted with zincon and are equivalent to the amount of sulphate present.     

Separation of lead sulphate from barium sulphate in their determination in glass

The conventional method for separation of lead from a combined lead and barium sulphate precipitate by extraction with ammonium acetate has been critically studied. The results show that quantitative separation of lead is possible only when the molar concentration ratio of barium to lead is 4.2 or above, but at ratios below 4.2 the method fails because of the formation of a solid solution of lead and barium sulphates which is maximal at initial mole-ratio 0.42. The lead in the solid solution, however, forms a strong soluble complex with EDTA and can be quantitatively separated. Based on this, a gravimetric method has been worked out for determination of lead and barium in glass.     

Kritische studie über die quantitative bestimmung von sulfat

The gravimetric sulphate determination as barium sulphate works well with the usual precautions and Schleicher & Schuell blue ribbon filters without any agents for increasing crystal size or coagulation effects. Interference by foreign metal ions may be overcome by use of synthetic ion exchange resins.Treatment of filter papers with hydrochloric acid before filtration of barium sulphate precipitates is not necessary. Ignition temperatures should be kept below 600 °C.Smaller amounts of sulphate are preferably determined by volumetric or micro-volumetric methods, by colorimetric methods, or by turbidimetric methods. A turbidimetric titration to maximum of turbidity has been described above.Good results are claimed.     

The titrimetric determination of sulphate,thiosulphate and polythionates in mining effluents

A titrimetric procedure is described for the determination of various forms of sulphur (sulphate, sulphite, thiosulphate, dithionate, tri- and tetrathionates after conversion to sulphate) in mining effluents. Metal ions are removed, after an oxidizing step, by a cationexchange resin, and the sulphate is precipitated with a known excess of 0.01 M barium chloride at pH 3.5. The excess of barium is back-titrated with standard 0.01 M ethylenediaminetetraacetic acid (EDTA) solution to a o-cresolphthalein complexone end-point at pH 11.0. The results obtained are in good agreement with those obtained by lengthy gravimetric procedures. Indirectly, dithionate can be determined, and sulphate and oxidizable thio salts such as thiosulphate and di-, tri-, and tetrathionates can be distinguished.     

Study on the preparation and formation mechanism of barium sulphate nanoparticles modified by different organic acids

This paper reports a simple method to prepare barium sulphate nanoparticles by use of tetradecanoic acid, hexadecanoic acid and stearic acid as modifier. The barium sulphate nanoparticles obtained are characterized by using Fourier transform infra-red spectroscopy (FT-IR), powder X-ray diffraction (XRD), transmission electron microscopy (TEM), dynamic laser light scatter (DLLS) and thermogravimetric analysis (TGA), respectively. The results show that the BaSO₄ particles are all spherical and in the nano-scale. Our method has a better dispersion and controllable diameter dependent on the length of the chain of organic acid and the pH value of the system. A possible mechanism is also discussed.     

Determination of Total Sulphur in Vegetation by a Turbidimetric Method Following An Oxygen-Flask Combustion

Abstract

A rapid method of determining total sulphur in vegetation is described. The plant material is combusted in an oxygen-flask, and the sulphate content of an aliquot of the absorbing solution is determined turbidimetrically as barium sulphate. The method is convenient and accurate. Its results agree closely with those obtained by the AOAC magnesium nitrate procedure.     

Potentiometrische Titration von Sulfat, Barium und Strontium mit Hilfe einer bleisensitiven Elektrode

Zusammenfassung Die bleisensitive Elektrode der Fa. Orion spricht neben Bleiionen auch auf Sulfationen an. Dies ermöglicht die potentiometrische Titration von Sulfat mit Bariumperchlorat sowie die Titration von Barium und Strontium mit Natriumsulfat. Der günstigste pH-Bereich liegt zwischen 5 und 7. Titriermedium sind Dioxan-Wasser-Gemische. Die Verfahren sind sehr empfindlich und erlauben in allen Fällen die Titration bis herab zu 5·10^–4 mMol.Anwendungsbeispiele für die Bestimmung von Schwefel in organischen Verbindungen nach Schöniger- oder Wickbold-Verbrennung sind angegeben.

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Potentiometric titration of sulphate, barium and strontium by means of a lead-sensitive electrode

The Orion lead electrode was found to be responsive not only to lead ions but to sulphate ions, too. This offers possibilities to titrate sulphate with barium perchlorate and reversely barium and strontium with sodium sulphate. The useful pH range is 5–7. Dioxan-water mixtures serve as solvents. The described methods are highly sensitive and allow determinations down to 5×10^–4 millimoles.Examples are given for the determination of sulphur in organic samples after combustion according to Schöniger or Wickbold.

     

Thermal decomposition of iron(II) sulphate heptahydrate in air in the presence of calcium,strontium and barium carbonates

The thermal decomposition in air of iron(II) sulphate heptahydrate in the presence of calcium, strontium and barium carbonates has been carried out. The decomposition path varies from carbonate to carbonate. Also, these decompositions are different from those of basic beryllium carbonate and basic magnesium carbonate. The results obtained for the kinetics of thermal decomposition have also been presented.     

Photometrische Bestimmung von Fluoriden im Trinkwasser mit Lanthan-Alizarin-Komplexan nach Abtrennung von Störionen mittels Kationenaustausch

The simple method described employs the direct detection as “alizarinfluorine-blue complex”. The interfering influence of high contents of sulphate and chloride can be eliminated by correction. Good reproducibility has been obtained when applying the method to very hard water samples, also in comparison with the values obtained by distillation.     

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.     

Determination of trace levels of sulphate in water using flow-injection and in-line preconcentration

Sulphate is preconcentrated on a strong anion-exchange resin and determined using the effect of sulphate ions on the complexation of methylthymol blue and barium. A computer-controlled flow-injection analyser is used to automate the whole procedure. The resin has two functions: it preconcentrates sulphate and also separates sulphate from divalent cations that may interfere in the determination step. The system can handle 30 samples per hour and has a working range from 25 to 1000 μg 1^?1 of sulphate. Lower detection limits can be obtained by changing the preconcentration conditions. The effect of both anionic and cationic interferents was studied.     

Evaluation of barium hydroxide treatment efficacy on a dolomitic marble

The Arch of Peace, by Luigi Cagnola, is one of the most famous neoclassical monuments in Milan. It has been subjected to conservative intervention in 1998. In the present paper the efficacy of the consolidation by means of barium hydroxide has been evaluated. The stone material showed severe degradation phenomena as: erosion, pulverisation, exfoliation. The analytical data acquired through X-ray diffraction (XRD), infrared spectrophotometry (FTIR) and scanning electron microscopy (SEM-EDX), allowed to compare the conditions of stone before and after the treatment with barium hydroxide. The presence of barium has been put in evidence mainly on the surface as barium sulphate, whereas barium is only sporadically present within the thickness of the decayed material. The treatment was judged not satisfying and its inefficacy is, most probably, due to a not suitable cleaning procedure carried out before the consolidation.     

Indirect Determination of Sulfate In A Nutritional Product Premix Using an Inductively Coupled Argon Plasma Spectrometer

Abstract

Inductively Coupled Argon Plasma Spectrometry (ICAP) has been used in a simple way to determine the sulfate content of a complex mixture. the method was based on the determination of excess barium after the sulfate in the mixture was selectively precipitated using a known amount of a standard barium chloride solution. the results obtained were in excellent agreement to those obtained using the conventional gravimetric method. A considerable time saving factor was also noted.     

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.     

氢氧化钡沉淀–碘量法对高锰酸钾和锰酸钾共存时的分别测定

采用氢氧化钡沉淀–碘量法对高锰酸钾和锰酸钾共存时的含量分别进行测定。向电解液中加入过量的饱和氢氧化钡溶液,利用锰酸钡和高锰酸钡溶度积的不同进行分离,再用碘量法分别对高锰酸钾和锰酸钾进行测定。结果表明,高锰酸钾和锰酸钾的检出限分别为0.061,0.077 g/L,测定结果的相对标准偏差分别为0.57%和0.72%(n=4),高锰酸钾的加标回收率为94.12%~95.85%。t检验结果表明,氢氧化钡沉淀–碘量法与传统方法对高锰酸钾和锰酸钾的测定结果无显著性差异。该法避免了亚铅酸钠和铬盐的毒性及滴定终点颜色不易判断等缺点,适合于高锰酸钾工业生产中主要成分的快速检测。     

Complexes of metallochromic substances. VII

Summary The dissociation constants of the sulphonazo III-proton complexes, and the composition and global stability constant of the sulphonazo III-barium(II) complex were determined. The optimum conditions for the spectrophotometric determination of barium(II) and sulphate ions by means of sulphonazo III were worked out. The determination of barium is the most sensitive and selective of all known spectrophotometric barium determinations.

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Zusammenfassung Die Dissoziationskonstanten der Sulphonazo III-Proton-Komplexe, sowie die Zusammensetzung und globale Stabilitätskonstante des Sulphonazo III-Barium(II)-Komplexes wurden festgestellt. Die optimalen Bedingungen für die spektralphotometrische Barium- und Sulfatbestimmung mit Hilfe von Sulfonazo III wurden ausgearbeitet. Die beschriebene Bestimmung von Barium stellt die empfindlichste und selektivste aller bekannten spektralphotometrischen Bariumbestimmungen dar.

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Part VI, see.