Thiomercurimetric determination of carbon disulphide, carbonyl sulphide, thiols and hydrogen sulphide by use of 1,3-diaminopropane and tributyltin chloride

A new approach to the determination of carbon disulphide and carbonyl sulphide in the presence of each other is based on the reaction with 1,3-diaminopropane (DAP), and titration with o-hydroxymercurybenzoie acid (HMB) before and after the selective decomposition of the COS-derivative at pH 4. Determination of hydrogen sulphide, thiols, carbon disulphide and carbonyl sulphide in the presence of each other in hydrocarbon solvents involves four titrations with HMB, viz. of all compounds after conversion of CS(2) and COS with DAP, of thiols plus H(2)S, of the thiols alone after removal of H(2)S by extraction, and of CS(2) alone after removal of other compounds by shaking with aqueous alkali. For selective trapping of H(2)S, HCN, RSH, CO(2) and CS(2) + COS, the sample gas is passed successively through a potassium antimonyl tartrate filter, a nickel carbonate filter, a tributyltin chloride filter, a bubbler containing 40% potassium hydroxide solution and a bubbler containing a benzene solution of DAP. The analysis is completed by titration with HMB with dithizone or dithiofluorescein as indicator.     

Thiomercurimetrische Bestimmung von Schwefelwasserstoff, Schwefelkohlenstoff und Thiolen in atmosph?rischer Luft

Zusammenfassung Die Bestimmungen beruhen auf der Anwendung von o-Hydroxymercuribenzoesäure (HMB), Dithiofluorescein and Tetraacetoxyquecksilberfluorescein (TMF). Es werden bestimmt: 1. Schwefelwasserstoff, 2. Schwefelkohlenstoff und Kohlenstoffsulfidoxid, 3. Thiole. Um Luftoxydation vorzubeugen, werden Zinksalze oder Triäthylbleichlorid zugesetzt. Ferner werden Absorptionsmittel für die selektive Absorption von H₂S und Thiolen sowie für H₂S und HCN beschrieben. Die Verwendung von TMF beruht darauf, daß freie TMF, Komplexe mit Cyaniden in wäßriger und alkoholischer Lösung sowie Komplexe mit Thiolen, Dithiound Thiocarbamidaten in alkoholischer Lösung stark fluorescieren, dagegen die Komplexe mit Sulfiden und s8-Hydroxychinolin keine oder nur sehr schwache Fluorescenz aufweisen.

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Thiomercurimetric determination of hydrogen sulphide, carbon disulphide and thiols in atmospheric air

The determinations are based on the application of o-hydroxymercuribenzoic acid (HMB), dithiofluorescein and tetraacetoxymercurifluorescein (TMF). The following compounds are determined: 1. hydrogen sulphide, 2. carbon disulphide and carbon sulphide oxide, 3. thiols. Air oxydation is prevented by using zinc salts or triethyllead chloride. Furthermore, absorbents are described for the selective absorption of H₂S and thiols and of H₂S and HCN. The use of TMF is based on the fact, that free TMF, complexes with cyanides in aqueous and alcoholic solution as also complexes with thiols, dithio- and thiocarbamidates in alcoholic solution show strong fluorescence, whereas complexes with sulphides and 8-hydroxyquinoline fluoresce only weakly or not at all.

     

Pro- and antioxidant characteristics of natural thiols

In aqueous solutions at physiological temperature, the mechanism of antioxidative action of natural thiols (glutathione, cysteine, and homocysteine) mainly involves reactions with reactive oxygen species (ROS), peroxyl radicals and hydrogen peroxide. Reduction of hydrogen peroxide by thiols is accompanied by radical generation. The kinetic characteristics of these processes, including those for the reactions of hydrogen peroxide and glutathione immobilized on solid supports such as sodium montmorillonite (clay) and cellulose were determined. Prooxidative effects of thiols are related with the reactions of thiyl radicals formed in the exchange reactions of thiols with other radicals and in the reactions between thiols and hydroperoxides. Thiyl radicals are known to react easily with double bonds. Resveratrol and caffeic acid, phenolic antioxidants containing double bond in their molecules, were shown to be consumed when reacted with glutathione and the process accelerated in the presence of hydrogen peroxide.     

Determination of sulphide, polysulphide, thiocarbonates and sulphur by extraction with tributyltin hydroxide, and of thiosulphate by hydrogenation

The methods presented involve the separation of sulphur compounds by means of a hexane solution of tributyltin hydroxide (TBT), followed by titration with o-hydroxymercuribenzoic acid in the presence of dithizone as indicator. Free sulphide is selectively extracted from strongly alkaline solution, whereas the polysulphides and thiocarbonates are extracted at pH 9-10. The polysulphide and thiocarbonate extracts decompose to form TBT-sulphide, sulphur and carbon disulphide. Treatment with sulphite, stannate(II), copper, vinyl cyanide and ethylenediamine, and hydrogenation with zinc and hydrobromic acid have been applied in the course of the analysis. The sulphur is determined by its attack on copper to form copper(I) sulphide which is subsequently dissolved in aqueous potassium cyanide solution and the sulphide separated by extraction.     

A study of the effect of some pollutant gases on cathodes used in membrane-covered amperometric oxygen detectors

The effects of various gaseous pollutants on the electrochemical activity of materials used as cathodes for membrane-covered amperometric oxygen detectors are described. It is shown that gold and platinum cathodes are not unduly affected by concentrations of sulphur dioxide and chlorine many times greater than those likely to be encountered in test solutions, and that a gold cathode is also unaffected by hydrogen sulphide. A platinum cathode is rapidly and significantly poisoned on contact with hydrogen sulphide; an analysis of the fall in the rate of oxygen reduction as a function of time indicates that the poisoning occurs by the blocking of surface sites by sulphide. The effect of hydrogen sulphide on silver, nickel and nickel sulphide electrodes is also reported. Of these materials, only nickel sulphide is an effective electrocatalyst for oxygen reduction in the presence of sulphide.     

Improved method of sampling and determination of traces of hydrogen sulphide

A sensitive spectrophotometric method for the determination of traces of hydrogen sulphide in environmental samples, after fixation as zinc sulphide, is reported. The method is based on the reaction between iodate and sulphide in the presence of excess of chloride ions. The resulting iodine chloride complex is ion-paired with Pyronine G and the product is extracted into benzene. The colour system obeys Beer's law over the range of 0.05–0.6 g of hydrogen sulphide. The coefficient of variation is 6.3% for 10 determinations of 0.3 g of hydrogen sulphide. The suitability of the method for monitoring hydrogen sulphide in atmospheric air in the vicinity of possible sources such as a sewage treatment plant and in wastewater has been evaluated.     

A gravimetric procedure for the determination of wet precipitated sulphur, dissolved sulphur, soluble sulphides and hydrogen sulphide

Elemental sulphur (in wet precipitated form or dissolved in organic solvents) and hydrogen sulphide have been determined gravimetrically at room temperature by conversion into copper sulphide by elemental copper in presence of an organic solvent such as benzene or acetonitrile. Any solvent in which sulphur is soluble can be used. The black copper sulphide formed can be weighed or determined iodometrically. Analysis indicates the black compound to be Cu(1.8)S. This room temperature method is a versatile one-step procedure sensitive to microgram or macro amounts of sulphur. It has been used for determining the solubility of sulphur in tetrahydrofuran and dioxan. The apparent heat of solution indicates that sulphur dissolves in these solvents without any marked solute-solvent interactions.     

Phase equilibria of hydrogen sulphide clathrate hydrates in the presence of single or mixed salt aqueous solution

This work reports the dissociation pressures of hydrogen sulphide clathrate hydrates in the presence of single and mixed aqueous solutions of NaCl, KCl and CaCl₂ at different temperatures and various concentrations of salt(s) in aqueous solution. The equilibrium data were generated using an isochoric pressure-search method. These data are compared with some selected experimental data from the literature on the dissociation conditions of hydrogen sulphide clathrate hydrates in the presence of pure water to show the inhibition effects of the aforementioned aqueous solutions. Comparisons between our experimental data and the corresponding literature data show some disagreements in the literature data.     

1,1,1-and 1,1,3-trihalo-2-sulfanylpropan-2-ols: New preparatively accessible synthons

A procedure has been developed for the synthesis of 1,1,1-trichloro-2-sulfanylpropan-2-ol and 1,1,3-tribromo-2-sulfanylpropan-2-ol via acid-catalyzed addition of hydrogen sulfide to the corresponding ketones. The stability of the resulting hydroxy thiols was estimated by analyzing the potential energy surface for the reaction of 1,1,1-trichloropropan-2-one with hydrogen sulfide in the presence of hydrogen chloride. In addition, quantum-chemical analysis of rotational isomerism of 1,1,1-trichloro-2-sulfanylpropan-2-ol was performed.     

Reaction of functionalised thiols with oligoisobutenes via free-radical addition.: Some new routes to thermoplastic crosslinkable polymers

The functionalisation of vinylidene (isopropenyl) terminated oligoisobutenes (polyisobutenes; PIB) with several thiols has been realised in the presence of free-radical generators. Oxygen (air) is a significant accelerator for this reaction and in some cases, alone, is sufficient to cause the reaction to occur. Free-radicals were generated from peroxydicarbonates, AIBN or UV irradiation. The reaction is of an anti-Markovnikov type with the RS-function adding to the vinylidene CH₂ group selectively in the presence of more substituted olefin groups in commercial PIB. A variety of thiols has been investigated and the synthesis of elastomeric polymers resulting from the hydrolysis and condensation of a trialkoxysilane coupled to PIB via a sulphide link has been demonstrated. The synthesis of comb-like polymers made by the addition of PIB to poly(mercaptopropyl methylsiloxane) has been achieved in a way to leave some non-reacted thiol functions available for crosslinking. A perfluoroalkyl thiol modified PIB shows a significant reduction in surface tension compared to the starting PIB polymer.     

STUDIES OF MECHANISM OF 2-METHYLTHIOPHENE AND THIOPHENE FORMATION FROM N-PENTANE AND HYDROGEN SULPHIDE USING 14C

Abstract

The mechanism of 2-methylthiophene formation from n-pentane and hydrogen sulphide over Cr-containing oxide catalyst is studied by using the Kinetic-Isotope method. The experiments were carried out in pulse system in He as a carrier gas (535° and 3 atm.) using ¹⁴C-labelled pentene and n-pentane. The reaction products were analyzed by radiochromatography. It is shown the 2-methylthiophene formation from n-pentane and hydrogen sulphide proceeds largely via consecutive dehydrogenation of n-pentane to pentenes, pentadiene followed by interaction with hydrogen sulphide. Thiophene is largely as a result of C₄-hydrocarbon interaction with hydrogen sulphide. A general scheme of the mechanism of 2-methylthiophene and thiophene formation is suggested.     

Simultaneous determination of nanomole amounts of sulphur dioxide and hydrogen sulphide by flow injection analysis with on-line preconcentration by means of capillary denuder tubes

A simple and rapid method for trace determination of SO2 and H2S in gaseous samples by using a flow injection system with on line preconcentration on capillary denuder is described. The gaseous samples are led through a 0.4 M sulphamic acid solution, retaining nitrogen dioxide, ammonia and hydrogen chloride. The sulphur dioxide is collected from the carrier gas stream (250 cm3 min-1) as sulphuric acid in a capillary denuder tube coated with a thin layer of 0.01-0.03 M hydrogen peroxide solution of 0.05 mM sulphuric acid; hydrogen sulphide passes into a second tube coated with 0.075 mM sodium sulphide solution of 0.1 M aqueous sodium hydroxide. The films containing the sulphuric acid and the sodium sulphide, respectively, are eluted with the corresponding circulating absorbent streams and pass through the detectors. Sulphuric acid is detected by conductimetry and sulphide is determined spectrophotometrically at 230 nm. If nanoequivalent amounts of H2S are present in the sample containing a large concentration of SO2 (SO2/H2S concentration ratio > 20), the sulphur dioxide is filtered out of the sample gas stream by solid sodium hydrogen carbonate. A limit of detection of 3.5 micrograms m-3 is obtained.     

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.     

硝酸、硫化钠溶液浸取冷原子荧光法选择性测定土壤及河流沉积物中硫化汞

本文研究了饱和硫化钠溶液对土壤样品中硫化汞的浸取效率(其加标回收率达100%),以及用硝酸和硫化钠溶液对样品中汞的选择性浸取并研究了土壤中硫化汞垂直分布。提出了利用硝酸、饱和硫化钠溶液浸取,由冷原子荧光法选择性测定土壤及河流沉积物中硫化汞的新方法。用该方法对同一样品进行8次测定,其相对标准偏差为7.1%。     

Coulometric generation of H+ ions by oxidation of thiols at a platinum anode and by oxidation of mercury in acetic acid—acetic anhydride

The coulometric generation of hydrogen ions by anodic oxidation of propane-1-thiol, butane-1-thiol, 2-mercaptopropionic acid, heptane-1-thiol, 2-mercaptoethanol, methyl and ethyl thioglycollate and p-thiocresol in acetic acid—acetic anhydride (1 + 6 v/v) is described, together with the possibility of coulometric generation of protons by mercury oxidation in the presence of p-thiocresol in the same solvent system.Current-potential curves for the solvent, indicator, titrated bases, mercury and the investigated thiols showed that in acetic acid—acetic anhydride (5 + 95, v/v), mercury and the investigated thiols are oxidized at potentials which are much more negative than those of the titrated bases and other components present in the solution.Titration of potassium hydrogenphthalate and sodium acetate with protons generated by the oxidation of thiols, and of sodium acetate, lithium acetate and pyridine with protons generated by the oxidation of mercury, demonstrated that the oxidation of both thiols and mercury proceeds quantitatively with 100% current efficiency.     

Differential pulse polarographic study of the degradation of cephalexin: Determination of Hydrogen Sulphide and other Degradation Products

Differential pulse polarography (d.p.p.) is used to study the degradation of cephalexin. Hydrogen sulphide, evolved during the degradation of cephalexin solutions, was removed continuously in a stream of nitrogen and determined periodically. Other electroactive degradation products were observed by d.p.p. of the degraded sample solutions. The degradation mechanism is highly dependent on pH, the initial concentration of cephalexin, temperature, the particular buffer used, and the presence of dissolved oxygen. The formation and degradation of the diketopiperazine derivative formed by intramolecular aminolysis, particularly at neutral pH, can be followed by means of its polarographic peak at -0.9 V (pH 7.4). Approximately half the total sulphur originally present in cephalexin is liberated as hydrogen sulphide at pH 7.4 at 37°C. Increasing the degradation temperature to 80°C and sweeping out the hydrogen sulphide with nitrogen increases the yield of a major product which gives a peak at -1.26 V. At pH 8.5 (80°C. 100 μg cephalexin ml^-1) the percentage of the sulphur evolved as hydrogen sulphide increases with time, and a peak appears at -0.96 V (probably 2-hydroxy-3-phenyl-6-methylpyrazine) which increases as the peak at -1.26 V becomes smaller. Other products formed under different conditions (concentration, pH, temperature) are reported. At pH 3 (80°C) only 8% conversion via intramolecular aminolysis and 5% evolution of total sulphur is indicated after four hours.     

Rhodium-catalyzed reductive coupling of disulfides and diselenides with alkyl halides, using hydrogen as a reducing agent

[reaction: see text] We have established that RhCl(PPh3)3 catalyzes a reductive coupling of disulfides and diselenides with alkyl halides in the presence of triethylamine using hydrogen as a reducing agent. This reaction serves as a convenient new method to produce unsymmetrical sulfides and selenides from disulfides and diselenides instead of unstable and odoriferous thiols and selenols.     

Determination of hydrogen sulphide and sulphur dioxide in a mixture

A method has been proposed for the determination of hydrogen sulphide and sulphur dioxide in a mixture. The method is based upon the quantitative oxidation of sulphide and sulphite with an excess of radiochloramine-T in alkaline medium /0.1N NaOH/. The released chloride activity is proportional to the total amount of sulphide and sulphite present. Addition of 1% CdSO₄ solution to the mixture of sulphide and sulphite precipitates sulphide, and sulphite in the filtrate determined by the reagent. From the difference in activities, the amount of sulphide can be calculated. This method can be employed for the determination of hydrogen sulphide and sulphur dioxide in air samples.     

X-ray photoelectron spectrometric and x-ray fluorometric studies of sulphur compounds on the surface of copper plates exposed to the atmosphere

X-Ray photoelectron spectroscopy (XPS) and XRF as techniques for monitoring air pollution are compared. Sulphide and oxides of sulphur (SO(2), SO(3) and SO(2-)(4)) have been determined on copper plates exposed for different lengths of time to an atmosphere containing hydrogen sulphide. The total amount of sulphur increases with the time of exposure but the sulphide reaches a constant value after 59 days. An interpretation of the mechanism of oxidation of hydrogen sulphide is offered.     

Extraction of gold, palladium and platinum from chloride, bromide and iodide solution with di-n-octyl sulphide (DOS) in cyclohexane

The extraction of gold, palladium and platinum from hydrochloric acid, hydrobromic acid and iodide media by solutions of di-n-octyl sulphide in cyclohexane was examined. From distribution data it was concluded that the monosolvates AuX(3).DOS and disolvates PdX(2).2DOS are extracted. Extraction of platinum was efficient only from iodide solutions; a disolvate PtI(4).2DOS was formed. The possibility of separation of gold and palladium from platinum by extraction from bromide or chloride solutions and simultaneous extraction of palladium and platinum from an iodide medium was demonstrated.