Determination of sulphur content in drill core samples by backscattered beta-particles and gamma-ray absorption

A relatively simple method of sulphur determination in drill cores of calcium carbonate matrix is described. The method is based on the combination of measurements of backscattered beta-particles and transmitted low energy gamma-radiation intensities. The transmitted gamma-radiation measurement corrects the errors of sulphur determination caused by the varying strontium sulphate and silicon dioxide content. The method has been tested on 170 samples. It was estimated that the standard deviation of sulphur determination does not exceed 2.5% of sulphur. The apparatus for routine absorption measurement is also described.     

Determination of Sulphur in Solid and Liquid Samples by Potentiometric Titration with Ion Selective Electrode.

Abstract

This paper describes a potentiometric method for the determination of sulphur in solid and liquid samples, using a sulphide ion selective electrode after the reduction distillation step. The determination of sulphide in solid and liquid samples without prior treatment was carried out by direct and titration potentiometric methods.

The reproducibility of the method and the recovery of sulphate in solid samples was investigated using analytical reagent grade 99% sodium sulphate. Portions of aproximately 100 mg of reagent were subjected to the reduction distillation process. After the ion selective electrode showed a stable value of the potential, indicating that all the sulphate had been reduced to sulphide, the potentiometric titration with lead nitrate solution was performed. A mean recovery of 98% of sulphate was found. The potentiometric titration method described in this work, can be applied to determine S⁼ in solid samples with the advantage that it does not require sample solubilization or extraction prior to the determination. The method yields an almost total reduction of sulphur and also a good precision.     

Analytical applications of condensed phosphoric acid-IV Iodometric determination of sulphur in sulphate and sulphide ores and minerals and other compounds after reduction with sodium hypophosphite and tin metal in condensed phosphoric acid

Sulphate in sulphate ores, e.g., alunite, anglesite, barytes, chalcanthite, gypsum, manganese sulphate ore, is reduced to hydrogen sulphide by the hypophosphite-tin metal-CPA method, if a slight modification is made. Sulphide ores, e.g., galena, sphalerite, are quantitatively decomposed with CPA alone to give hydrogen sulphide. Suitable reducing agents must be used for the quantitative recovery of hydrogen sulphide from pyrite, nickel sulphide, cobalt sulphide and cadmium sulphide, or elemental sulphur is liberated. Iodide must be used in the decomposition of chalcopyrite; the copper sulphide is too stable to be decomposed by CPA alone. Molybdenite is not decomposed in CPA even if reducing agents are added. The pretreatment methods for the determination of sulphur in sulphur oxyacids and elemental sulphur have also been investigated.     

Determination of the elemental sulphur content of minerals and ores

A new technique has been developed to determine trace quantities of elemental sulphur in minerals and ores. After separation from the sample by sublimation, the sulphur is determined spectrophotometrically in ethanol. Sulphide, sulphite, sulphate and thiosulphate do not interfere. The effect of the presence of xanthate or dixanthogen is discussed briefly.     

Determination of trace amounts of sulphur in selenium

Determination of trace amounts of sulphur as Methylene Blue after reduction of sulphate to sulphide by hydriodic and hypophosphorous acids in acetic acid solution is applied to the determination of trace amounts of sulphur in selenium after removal of the selenium by evaporation with hydrobromic acid. Samples of 100 mg or less of selenium are chosen if the sulphur content is greater than 5-10 ppm; the time required for the separation is about 1.5 hr; 100 ppm of sulphur has been determined with a coeffident of variation of 5.2%. If the sulphur content is less than 5 ppm, 1-g samples must be taken and the time required is then about 3 hr; 0.4 ppm of sulphur has been determined with a standard deviation of 0.13 ppm. The accuracy of the method seems to be well within the random error.     

Indirect polarographic microdetermination of sulphur in organic compounds

A polarographic method for the microdetermination of sulphur in organic compounds is described; it is based on oxygen-flask combustion to yield sulphate, which is then reacted with excess of barium dichromate solution in hydrochloric acid, followed by adjustment to pH 12, collection of the combined barium chromate and sulphate precipitate, and polarographic determination of the free chromate (equivalent to the sulphate originally present).     

A contribution to the use of thorin as an analytical reagent: spectrophotometric study of its complexation with barium and application to sulphate determination in atmospheric particulates

The complexation of Ba(2+) by Thorin in the pH range 2-9 in aqueous ethanol medium has been investigated. The dissociation constants of Thorin in the ethanolic medium have been determined spectrophotometrically and the distribution of the protonated species has been used to explain the behaviour of the apparent complexation constant. On the basis of the apparent constants found, and mass-balances, the effect of sulphate on the absorbance has been calculated, and the best conditions for determination of sulphate have been established. Cation and anion interferences have been studied and means of overcoming them are proposed. The method developed has been applied to sulphate determination in atmospheric particulates. As little as 1 mug of sulphate can be measured.     

Accurate determination of sulphur in steels and certain heat-resisting alloys by isotope dilution mass spectrometry

A mass spectrometric isotope dilution method for the determination of sulphur in steels and certain alloys has been investigated. Addition of bromine in the dissolution of carbon steels was necessary for the complete conversion of sulphur into sulphate. The relative standard deviation was better than 1.5% for sulphur contents in the range 40-3,000 ppm. The results on standard materials were in good agreement with the certified values for samples of BCS, but lower than those for JSS and NBS.     

Die bestimmung des gesamtschwefels in vulkanisierten gummimischungen

A method is described in which by means of a resin ion-exchanger the interference of foreign cations, particularly iron and chromium, can be prevented in the determination of total sulphur in vulcanized rubbers. The procedure allows the use of rapid volumetric methods for determining sulphate even when analyzing mixtures containing iron oxide or chromium oxide pigments. Here, the sulphate is precipitated with benzidine and determined by titration with sodium hydroxide solution. The method is quicker and more certain than the usual barium sulphate gravimetric procedure.     

Determination of thioacetamide by oxidation with chloramine-T

Chloramine-T oxidises thioacetamide quantitatively in an alkaline medium in the hot, converting the entire sulphur into sulphate. A back-titration method, making use of this oxidation reaction, has been suggested for the determination of thioacetamide.     

Application of microwave heating to the determination of free, combined and total sulphur in rubber

An atomic absorption spectrometry (AAS) method for the determination of total and combined sulphur in rubber and a catalytic method for the determination of free sulphur in rubber are described. The catalytic method is based on the iodine-azide reaction and is followed by an extraction of free sulphur with benzene, toluene or acetone. The catalytic determination, with the aid of gas chromatography, was performed in N,N-dimethylformamide after expelling the more volatile solvents used in the extraction. The calibration is linear over the range 2 × 10⁻⁶ – 3 × 10⁻⁴ M. Before the determination of total and combined sulphur, the rubber samples were decomposed by microwave assisted heating (5 min, 110 W) in a Teflon closed vessel. After microwave heating the solution was clear and homogenous and all sulphur compounds contained in the rubber were quantitatively oxidized to sulphate. The sulphates were then precipitated as BaSO₄ and an excess of barium was determined by AAS. From the difference in the results of the determinations of total and free sulphur the amount of combined sulphur can be calculated, and from the difference in the determinations of total and combined sulphur the amount of free sulphur can be calculated. In the latter case the catalytic analysis is not needed.     

A new procedure, based on combustion to sulphate and ion chromatography for the analysis of elemental sulphur in sediments

Summary A procedure exploiting the bomb preparation method for the analysis of total sulphur in organic materials has been developed for the determination of zero-valent sulphur (S^o) in sediments. Sediment samples were dried over magnesium oxide and sonicated in the presence of toluene to extract S^o. Toluene solutions were directly oxidized by combustion in a bomb containing sodium carbonate-bicarbonate buffer, which trapped sulphur species generated from S^o as sulphate ions. These were in turn analysed by suppressed anion chromatography with ion-conductivity detection. The method was used to determine the distribution of S^o in saltmarsh sediment cores.     

Determination of total sulphur in fuel oils by ion chromatography

A method is described for the determination of total sulphur in fuel oils. The oils are burnt in an oxygen flask and the resulting sulphur dioxide is oxidised with hydrogen peroxide to sulphate which is subsequently determined by ion chromatography. With a 50-mg oil sample the limit of detection is 0.007% sulphur. The procedure is simple and has a r.s.d. of 2.7%. Blanks are negligible and the only interferences can be from metal ions that form insoluble sulphates. The method is compared with m.e.c.a, x.r.f. and titrimetric procedures.     

Determination of thiourea and its methyl derivatives by hypoiodite oxidation, and iodine monochloride end point; iodine bromide end point in the titration of thiourea with iodate

Summary Procedures have been described for the quantitative determination of thiourea and its methyl derivatives, wherein iodate, permanganate, and ceric sulphate have been used as direct titration solution, either following preoxidation by alkali hypoiodite via (ICI + KOH) or in case of thiourea, by iodine bromide method. Apart from using standard oxidants the methods have an added advantage of a high conversion factor due to oxidation of sulphur to sulphate. Alternative physical methods of detecting the end point is an added feature of these procedures.The authors wish to express their grateful thanks to Dr. S. S. Joshi, D. Sc. (London), for his kind interest in the work.     

Complexometric determination of sulphur in pyrites and sulphides

Summary An indirect complexometric method for the determination of sulphur in pyrites and other sulphides is proposed. Sulphur is converted to sulphate by fusion with sodium peroxide, sulphate is precipitated by lead solution at pH 4 and the excess of lead nitrate is back-titrated by EDTA solution in the presence of Xylenol Orange as indicator. The method has been successfully used for numerous sulphur determinations in pyrite, copper, lead and zinc concentrates.

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Zusammenfassung Es wird eine indirekte komplexometrische Methode zur Schwefelbestimmung in Pyriten und anderen Sulfiden beschrieben. Hierbei wird der Schwefel durch eine oxydierende Schmelze mit Na₂O₂ in Sulfat übergeführt, das Sulfat mit Bleinitrat bei pH 4 gefällt und der Überschuß an Bleinitrat mit ÄDTA gegen Xylenolorange zurücktitriert. Zahlreiche Schwefelbestimmung wurden mit gutem Erfolg in Pyrit sowie Kupfer-, Blei- und Zinkkonzentraten durchgeführt.

     

Substoichiometric isotope-dilution determination of sulphur after conversion to methylene blue and ion-pair extraction with dodecyl sulphate

The proposed substoichiometric determination of sulphur includes two key steps: conversion of sulphur to methylene blue and ion-pair extraction of methylene blue into chloroform with a substoichiometric amount of dodecyl sulphate. The method, combined with isotope dilution is applied to the determination of total sulphur in NBS SRM Citrus Leaves and in a seaweed sample (Laminaria religiosa Miyabe). The mean values obtained were 0.401±0.008% S (RSD 2%; n=9; certified value 0.407±0.009%) for the SRM, and 0.756±0.012% S (RSD 1.6%; n=5) for the seaweed. A sample of 0.5–1 g containing ca. 100 μg of sulphur can be analysed.     

Zur colorimetrischen Bestimmung flüchtiger Schwefelverbindungen in Lebensmitteln

The quantitative determination of volatile mercaptans and hydrogen sulphide with bis-(p-nitrophenyl)-disulphide is described. The influence of various other volatile sulphur compounds, which may be found in food, and of ethanol has been examined. It is possible to determine down to 0.1 mMol/kg of mercaptans and hydrogen sulphide in food with a standard deviation of 8.4%. A few examples are given.     

The spectrophotometric determination of sulphate after its extraction with methyltricaprylammonium chloride into cyclohexane

Improvements are described to Flynn's procedure for the extraction of sulphate with Aliquat-336 and its subsequent determination as sulphuric acid. A single-point photometric measurement with sodium 2,4-dinitrophenate is applied to the determination of sulphate (ca. 10 mg kg^?1) in soils, and also in sulphur in organic compounds after oxygen flask combustion.     

A new reagent for the detection and determination of small amounts of the sulphate Ion

An aqueous solution of 2-aminoperimidine hydrochloride is proposed as a new reagent for the detection and determination of the sulphate ion. As little as 0.05 p.p.m. can be detected by precipitation of the corresponding amine sulphate. Suspensions of the precipitate show remarkable stability and no colloidal stabilizers are needed. The reagent is applied to the nephelometric determination of 0.1–5 p.p.m. of sulphate ion; at the 0.5 p.p.m. level, the relative standard deviation is 4.5%. Although many ions form precipitates with the reagent at high concentrations, very few of the common anions provide significant interference in the nephelometric determination. The reagent seems promising for the determination of sulphate in natural waters, and for traces of sulphur in organic compounds after oxygen flask combustion.     

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.