Determination of polythionates and thiosulphate in mining effluents and mill circuit solutions

A method is described for the determination of total polythionates plus thiosulphate by acidimetric titration. The titration can be carried out either at the Methyl Orange (pH = 4.30) or at the phenolphthalein (pH = 8.20) end-point, with standard sodium hydroxide solution, to determine the amount of acid produced on oxidation of the thiosulphate and polythionates. The precision and accuracy are good and samples containing as little as 0.1 mg of the thio salt can be analysed very easily. Results obtained by this method are compared with those obtained by a calorimetric method and are in good agreement.     

Direct titrimetric determination of thiosulphate,sulphite and tin(II) with copper sulphate solution

Summary Standard copper sulphate solution has been successfully used for the direct titration of dilute solutions (0.05N) of thiosulphate, sulphite or tin(II) in presence of potassium iodide (5–7%) and starch. The method is sensitive and precise.

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Zusammenfassung Eine Standardlösung von Kupfersulfat läßt sich mit Erfolg für die direkte Titration verdünnter Lösungen (0,05N) von Thiosulfat, Sulfit oder Sn(II) in Gegenwart von 5–7% KJ und Stärke verwenden. Das Verfahren ist empfindlich und genau.

     

Oxidation of sulphide minerals-III determination of sulphate and thiosulphate in oxidised sulphide minerals

A method has been developed to determine sulphate and thiosulphate in small amounts of the oxidation products of sulphide minerals. The sample is treated with ammonium sulphide solution to promote ion-exchange between sulphide ion and the sulphur-bearing anions of the oxidation products. Sulphate is determined alone and then all other sulphoxy anions are oxidized to sulphate and determined as such. The non-sulphate anions are reported as thiosulphate. The relative error is about 10% or less for 2 mg or more of sulphoxy anion. Although this method does not yield exact results with respect to sulphite or polythionates, a clearer understanding of the oxidation of sulphide minerals is now available.     

Cerimetric determination of dithionate and polythionates

Ceric sulphate in a boiling strongly acidic medium oxidizes dithionate as well as tri- and tetrathionates quantitatively to sulphate. These anions may therefore be determined cerimetrically when they are present singly. A combination of the cerimetric method with other known methods (e.g. those of Kurtenacker, etc) is suggested for the analysis of mixtures of polythionates and dithionate.     

The titrimetric micro determination of sulphate using lead nitrate as titrant and dithizone as indicator

Summary The previously reported titrimetric determination of sulphate, using lead nitrate as titrant and dithizone as indicator has been developed for application to the micro scale. Attention has been directed in the titration procedure to the effect of foreign ions and their removal where necessary, the optimum conditions for the highest accuracy, and the precision attainable for the range 0.5 to 5 mg of sulphate (0.16 to 1.6 mg of sulphur). This procedure forms a highly satisf actor y basis for the micro determination of sulphur in organic compounds by oxidation with nitric acid in a sealed tube and subsequent titration of the sulphate ion produced.The procedure has also been extended to the submicro scale giving a direct titration of 10 to 100g of sulphate (4–30g of sulphur), thus enabling the sulphur content of submicro quantities of organic compounds to be readily determined.

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Zusammenfassung Die kürzlich veröffentlichte Methode der maßanalytischen Schwefelbestimmung mit Bleinitrat unter Verwendung von Dithizon als Indikator wurde dem Mikromaßstab angepaßt. Auf die Störung durch Fremdionen und deren gegebenenfalls notwendige Entfernung wurde Bedacht genommen, die optimalen Bedingungen für größte Genauigkeit für den Bereich von 0,5 bis 5 mg Sulfat (0,16 bis 1,6 mg Schwefel) ermittelt. Das Verfahren bietet einen sehr befriedigenden Weg für die Mikrobestimmung des Schwefels in organischen Substanzen durch deren Oxydation mit Salpetersäure im geschlossenen Rohr und nachfolgende Titration des Sulfats.

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Rèsumè La méthode précédemment décrite pour le dosage titrimétrique des sulfates à l'aide de nitrate de plomb comme réactif titrant et de dithizone comme indicateur a été étendue au domaine microanalytique. La technique de titrage a été particulièrement étudiée des points de vue de l'effet des ions étrangers et de l'éventuelle nécessité de leur élimination, des conditions optimum pour atteindre l'exactitude la plus élevée et pour déterminer la précision qu'il était possible d'obtenir pour le domaine de 0,5 à 5,0 mg de sulfate (0,16 à 1,6 mg de soufre). Cette technique est extrêmement satisfaisante pour son application au microdosage du soufre dans les composés organiques après oxydation par l'acide nitrique en tube scellé et titrage ultérieur de l'ion sulfurique formé.

     

Sampling and analysing mixtures of sulphate, sulphite, thiosulphate and polythionate

Interpreting the redox chemistry of sulphur in aqueous systems requires the analysis of mixtures of various sulphoxy anions. Previous methods have been too involved to permit high sample throughout if good quality control is to be maintained. Methods based on ion chromatography have been developed for the direct determination of SO(2-)(4), SO(2-)(3), S(2)O(2-)(3), and SCN(-). The determination of thiocyanate permits the indirect determination of polythionates by treatment with cyanide. Formate, acetate, F(-), Cl(-), CO(2-)(3), and PO(3-)(4), do not interfere, but NO(-)(2) and NO(-)(3) interfere with determination of SO(2-)(3),. The sample preservation treatment includes addition of formaldehyde, cation-exchange and cold storage, to retard oxidation of S(2)O(2-)(3), and SO(2-)(3), and inhibits the rearrangement of SO(2-)(3),/S(2)O(2-)(3),/S(n)O(2-)(6), mixtures caused by bimolecular nucleophilic displacement (S(N)2) reactions. Treated samples may be stored for up to 6 weeks with only minor loss of thiosulphate.     

Quenching and liquid chromatographic determination of polythionates in natural water

Polythionates in highly acidic, crater-lake water have been determined by ion-chromatography and high-performance microbore liquid chromatography. The first technique allows the determination of tri-, tetra- and pentathionate in excess of 10 ppm, and the second allows analysis for tetra-, penta- and hexathionate in excess of 0.2 ppm. The methods for preserving polythionates in natural solutions are also discussed. The recommended procedures for storage are to add hydroxylamine hydrochloride to sample solutions or to exclude atmospheric oxygen by using Winkler oxygen-determination bottles, followed by storage in a refrigerator at 5 degrees .     

Determination of sulphide, sulphite and thiosulphate with thallic perchlorate or sulphate

Sulphide, sulphite and thiosulphate can be determined separately or in admixture, with thallic perchlorate or sulphate in acid medium. A sample solution is rendered approximately 0.5 M in acid, 5 ml of 0.05 M KI are added and the solution is titrated to a starch end-point with thallium(III) solution. In another method an acid sample solution is titrated with thallium(III) or iodine solution in the presence of indigo carmine indicator. The end-point is improved in the presence of Co(II).     

Microanalysis of sulphide, sulphite, sulphate and thiosulphate by thin-layer chromatography and ring-colorimetry

Clean and rapid analytical separations of microgram quantities of S(2-), SO(3)(2-), SO(4)(2-) and S(2)O(3)(2-) ions have been accomplished by ascending thin-layer chromatography on microcrystalline cellulose with n-propanol-1M ammonia-acetone (30: 20: 2) as the solvent system. The separated species have been determined by ring-colorimetry.     

The small-scale titrimetric determination of complex cyanides

Summary Ferrocyanide, or ferricyanide after reduction, may be precipitated as uranyl ferrocyanide, the precipitate decomposed with alkali, and the uranium corresponding to the complex cyanide determined titrimetrically by standard methods. An alternative method, which can also be applied to cobalticyanide, is to decompose the precipitate produced with iron(II) ion, and to determine the resulting iron(III) by standard procedures. Alternatively, a known excess of iron(II) may be added, and the excess determined titrimetrically. The method may be applied to amounts of 1–100 mg of the complex ion, titrations are of the order of 1–6 ml, and relative errors over the stated range are of the order of ±2%.

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Zusammenfassung Cyanoferrat(II) oder Cyanoferrat(III), nachdem dieses reduziert wurde, lassen sich bestimmen, indem man als Uranylcyanoferrat(II) fällt, den Niederschlag mit Alkali zersetzt und die äquivalente Uranmenge nach einer Standardmethode titriert. Ein anderer Weg, der auch für die Bestimmung von Cyanokobaltat geeignet ist, führt über die Zersetzung des mit Eisen(II) erhaltenen Niederschlages und die Bestimmung des dabei entstandenen dreiwertigen Eisens nach Standardmethoden. Schließlich kann man einen gemessenen Überschuß Eisen(II) zusetzen und diesen titrieren. Das Verfahren eignet sich für 1 bis 100 mg Komplexion. Dabei werden 1 bis 6 ml Maßlösung verbraucht. Der relative Fehler beträgt ±2%.

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Résumé On peut précipiter les ferrocyanures, ou bien les ferricyanures après réduction, à l'état de ferrocyanure d'uranyle, décomposer le précipité par une base et doser par titrimétrie, au moyen de méthodes classiques, l'uranium correspondant au cyanure complexe. Une variante de la méthode, également applicable aux cobalticyanures, consiste à décomposer le précipité obtenu avec l'ion Fe-II et à doser le fer-III résultant suivant des procédés classiques. Une autre variante consiste aussi à ajouter un excès connu de fer-II et à doser l'excès par titrimétrie. On peut appliquer la méthode aux quantités de l'ordre de 1 à 100mg d'ion complexe et opérer sur 1 à 6ml environ avec des erreurs relatives de l'ordre de ±2% sur le domaine en question.

     

Spectrophotometric and titrimetric determination of catecholamines

Ammonium metavanadate is used to determine adrenaline, noradrenaline, isopropylnoradrenaline and methyldopa by titrimetric and photometric procedures. Oxidation of these catecholamines produces aminochrome derivatives which can be measured spectrophotometrically at 485 nm. Beer's law is obeyed over the ranges 0.09-0.90 mg for adrenaline, 0.07-0.65 mg for noradrenaline, 0.07-0.75 mg for isopropylnoradrenaline and 0.10-0.95 mg for methyldopa.     

The titrimetric determination of calcium and magnesium in silicate rocks

A cation-exchange scheme is described for the separation of calcium and magnesium from interfering elements in rapid silicate analysis. Interfering elements can be eluted from the ammonium form of Zeo-Karb 225 with a solution of the ammonium salt of ethylenediaminetetraacetic acid at pH 4.5. Calcium and magnesium are not eluted with this reagent but can be eluted consecutively with ammonium chloride solution and titrated photometrically with EDTA. Calcium and magnesium can be separated quantitatively from Al, Fe, Ti, Mn, Bi, Cd, Cr, Co, Cu, Pb, Mo, Ni, U, V, rare earths, and Zn.     

Hydrazine sulphate as reagent for titrimetric determination of vanadium(V) and chromium(VI)

Conditions have been developed for the direct titration of vanadium(V) and chromium(VI) with hydrazine sulphate, barium diphenylaminesulphonate being used as indicator and osmium tetroxide as catalyst.     

Extraction titrimetric determination of copper

Lead xanthate undergoes a quantitative, stoichiometric and fast exchange reaction with copper(II), even near the equivalence point, making it a suitable reagent for an extraction titration of copper. Many other metal ions do not participate in exchange reactions with lead xanthate. making this method selective for copper.     

The determination of sulphate in superphosphate

An accurate method developed by means of a statistical approach, has been devised for the quantitative determination of sulphate in superphosphate fertilizer. The method proved to be dependent of the source of raw phosphate used in the preparation of the superphosphates amined. A standard error of two parts per thousand has been obtained and it is claimed that the method is capable of determining the existence of sources of bias, if any.     

The spectrophotometric determination of antimony in water,effluents, marine plants and silicates

A spectrophotometric procedure is described for the determination of antimony in natural waters (including sea water and effluents), algae and silicates. After a preliminary oxidative digestion for waters, or acid attack for algae and silicates, the element is quantitatively coprecipitated at pH 5.0 with hydrous zirconium oxide. The precipitate is dissolved in acid, and, after reduction with titanium(III) chloride, antimony is oxidized to antimony(V) with sodium nitrite. The ion pair of the SbCl₆^- ion with crystal violet is extracted with benzene and its absorbance is measured at 610 nm (molar absorptivity 74,000 l mol^-1 cm^-1). Extraction with toluene causes some loss of sensitivity. The detection limit is 0.005 μg l^-1; relative standard deviations are 0.5% and 1.1% for spiked distilled water (0.5 μg l^-1) and sea water (0.26 μg l^-1), respectively. A wide range of anions and cations cause no interference at levels many times those in natural waters. The technique can be adapted for application to marine algae and silicates; relative standard deviations are 1.8% and 2% for samples of Pelvetia canaliculata (0.19 μg Sb g^-1) and a Pacific Ocean red clay (1.08 μg Sb g^-1), respectively. Results for the U.S. Geological Survey Standard rocks GSP1 (2.7 ppm) and DTS1 (0.53 ppm) are in good agreement with those of earlier workers.     

The spectrophotometric determination of arsenic in sea water,potable water and effluents

Procedures are described for the determination of arsenic in sea water, potable waters and effluents. The sample is treated with sodium borohydride added at a controlled rate. The arsine evolved is absorbed in a solution of iodine and the resultant arsenate ion is determined photometrically by a molybdenum blue method. The time required for a complete analysis is about 90 min, but of this only 15 min is operator time. For sea water the range, standard deviation, and detection limit are 1–4 μgl^-1, 1.4 % and O.14 μg l^-1, respectively; for potable waters they are 0–800 μg l^-1, about 1 % (at 20μg l^-1 level) and 0.5μg l^-1, respectively. Silver and copper cause serious interference at levels of 0.5 mgl^-1, and nickel, cadmium and bismuth interfere at concentrations of a few tens of mg l^-1; however, these elements can be removed either by preliminary extraction with a solution of dithizone in chloroform or by ion exchange. Arsenic present in organo-arsenic compounds is not directly determinable, but can be rendered reactive either by photolysis with ultraviolet radiation or by oxidation with permanganate or nitric—sulphuric acid mixture. Arsenic(V) can be determined separately from total inorganic arsenic after extracting arsenic(III) as its pyrrolidine dithiocarbamate into chloroform.