A sensor for hydrogen sulphide

A sensor for hydrogen sulphide is described. It is based on the catalytic effect of the gas on the iodine-azide reaction. An iodine-azide solution is exuded from a sintered-glass ball (10mm diameter) at a flow-rate of 3.30 ml min whilst its potential is monitored by two platinum electrodes. one inside and the other outside the ball. Sample is carried in a gas at a flow-rate of 350 ml min . Carbon disulphide, methyl mercaptan or sulphur dioxide in amounts up to a hundred times that of the hydrogen sulphide do not interfere. The detection limit is 5 ng and the determination limit is 8 ng, with a relative standard deviation of 10%.     

Extraction-spectrophotometric determination of hydrogen sulphide

A sensitive spectrophotometric method for the determination of trace amounts of hydrogen sulphide (H2S) after fixing in a modified zinc acetate-disodium ethylenediaminetetraacetate-sodium hydroxide solution is described. The fixed H2S is stable for 3 d. The reaction of iodate with H2S in the presence of acid and an excess of chloride leads to the formation of ICI which is stabilised as ICI2-. The species formed reacts with 2',7'-dichlorofluorescein to form 2',7'-dichloro-4',5'-diiodofluorescein which is extracted into a mixture of 15% isoamyl acetate in isoamyl alcohol. The colour system obeys Beer's law in the range 0-2.5 micrograms of H2S. The coefficient of variation is 4.5% for ten determinations of 2.0 micrograms of H2S. The effect of interfering gases on the determination is discussed. The method was applied to the determination of residual amounts of H2S present in a laboratory fume cupboard and the results obtained were compared with those given by the widely used Methylene Blue method. The method can be used to determine down to 0.3 micrograms of H2S.     

Optical fibre sensor for hydrogen sulphide monitoring in mouth air

A reversible optical fibre chemical sensor for hydrogen sulphide monitoring in mouth air based on reflectance measurements has been developed. The active sensing phase has been prepared by immobilising the colorimetric reagent 2,6-dichlorophenolindophenol (DCPI) in a silica gel support. The principle of the determination is based on the increase of reflectance of such solid sensing phase when hydrogen sulphide reduces the colorimetric reagent with the subsequent decolouration process. The addition of 1.26 μg of Cu(II) per gram of solid support improved the response time and reversibility of the sensing phase.The detection limit is 10 ppb (v/v) of hydrogen sulphide. The linear range using the Kubelka-Munk function extends at least up to 1000 ppb (v/v). The sensor exhibits a response time of less than 2 min for hydrogen sulphide concentrations in the linear range and the signal is reversible.The optical sensor has been successfully tested for human malodour monitoring and the results validated by comparison with those obtained for the same individuals using a commercially available electrochemical instrument.     

Electrochemical determination of hydrogen sulphide in air

A new method for the quantitative analysis of sub-ppm and high ppm levels of hydrogen sulphide is reported. The technique is based on the electrochemieal oxidation of hydrogen sulphide at a potentiostatically-controlled. Teflon-bonded diffusion electrode. Two instruments (one portable and one a fixed-location instrument) were constructed and their operating characteristics evaluated. They were sensitive and selective, responded rapidly to the gas. and gave a linear relationship between steady-state signal and gas concentration. Excellent zero and signal stability indicate that the electrochemical sensor is not poisoned by the H(2)S.     

Simultaneous absorption of hydrogen sulphide and carbon dioxide into potassium carbonate solution with or without amine promoters

Simultaneous absorption of hydrogen sulphide and carbon dioxide into potassium carbonate and amine-promoted potassium carbonate solutions has been perf     

Complex hydrogen bonded cations - VI cations involving aliphatic bases

Hydrogen bond complexing between aliphatic bases and their cations has been examined by infrared spectroscopy. The results are: Morpholinium/morpholine - strong complex - asymmetric single minimum bond (a.s.m.). Piperidinium/piperidine - strong complex (a.s.m.). Piperidinium/NMe morpholine - complex (a.s.m.). NMe piperidinium/morpholine - weaker complex (a.s.m.). NMe piperidinium/NMe piperidine - no complexing. NMe morpholinium/NMe morpholine - no complexing. Triethylenediamine (TED). Complexes of type (TEDH⁺)_n, and TEDH⁺/TED have been distinguished.Models indicate the Me group retains the equatorial position in the tertiary bases on complexing, and the N β N distance is ? 2.5 Å.     

A flow analysis system with an amperometric detector for the determination of hydrogen sulphide in waters

 A flow analysis system with an amperometric H₂S detector and a gas extraction unit as well as an integrated coulometric calibration unit is described, which allows an on-line determination of hydrogen sulphide in aquatic samples. By variation of different parameters (e.g. flow rate, gas injection volume, pH of solution) a wide dynamic working range of concentrations from 1 μmol/l H₂S to 750 μmol/l is accessible. The sampling rate is about 36 samples h⁻¹ using an average flow rate of 1.78 ml/min and a gas injection volume of 28 μl. The measuring system is designed as a portable device. In combination with the polyethylene-tube of a PTFE-underwater pump field-measurements on board are possible. Received: 16 February 1995/Revised: 5 April 1995/Accepted: 11 April 1995 Acknowledgements. This work was supported by the Bundesminister für Forschung und Technologie under the project “DYSMON II” (03F0123D) and by the Fonds der Chemischen Industrie zur F?rderung von Chemie und Biologischer Chemie. Correspondence to: P. Jeroschewski     

A CASPT2 study of the dipole moment surfaces of hydrogen sulphide molecule

The ability of the CASPT2 method to yield accurate H₂S dipole moment surfaces that could be further used for conclusive predictions about rovibrational calculations, has been evaluated using ANO-L basis set. The optimised geometry, permanent dipole moment, linearity barrier as well as general features of the μ_x and μ_z dipole moment components in the vicinity of the equilibrium configuration agree favourably with available empirical determination and with recent accurate ab initio calculations. Dipole moment functions behaviour is also well reproduced for those geometrical configurations which are far from equilibrium in dissociation path. Computational technical aspects are discussed.     

Complexes of small neutral gold clusters and hydrogen sulphide: A theoretical study

Binding energies, geometries, charge transfers and vibrational frequencies of complexes of neutral gold clusters Au_n (n = 1–4) and H₂S are computed using density functional theory. The geometries of Au_n and H₂S are little changed upon complex formation but, for the Au₄SH₂ complex, one of the two low-lying Au₄ isomers is more stabilized by H₂S due to intracomplex hydrogen bonding and may be the lowest-energy Au₄SH₂ structure. For the complexes, computed infrared and Raman spectra are discussed with a focus on distinguishing between the two candidates for the lowest-energy Au₄SH₂ structure.     

Application of radiochloramine-T for the determination of trace amounts of hydrogen sulphide

Hydrogen sulphide at trace level can be determined by radiorelease technique using radiochloramine-T. The minimum detection level is 0.25 ppm. Zinc acetate is used to fix H₂S from air samples. CS₂ does not interfere. Interference by SO₂ can be eliminated by oxidizing it with H₂O₂.     

纸带-光纤技术对硫化氢气体测量的初探

以研制的光导纤维反射分光光度计为仪器,建立了根据浸渍醋酸铅的纸带与硫化氢反应生成黑色硫化铅斑点而改变纸带相对反射率,达到对H2S测量的新方法。测量波长为450nm,测量H2S浓度范围为5×10-8mol/L～1.35×10-6mol/L。方法可用于测量废气中的硫化氢。     

Temperature dependence of the Kerr effect of hydrogen sulphide

The Kerr effect fo gaseous hydrogen sulphide was measured from 254–341 K and (1.5–16.7) ×10⁵ Pa. The difference between the polarizability in the direction of the molecular dipole and the mean is (?0.029 ± 0.008) × 10^?40 C² m² J^?1. With literature data, this yields all three principal polarizabilities. The first hyperpolarizability β^K is obtained.     

Optosensing of hydrogen sulphide through paper impregnated with lead acetate

Summary A flow-through optosensing method for hydrogen sulphide analysis is described, which involves reflectance measurements through optical fibres on paper impregnated with lead acetate. Levels as low as 50 ppb H₂S could be measured with high reproducibility within 10 s. The response was affected by flow rate and relative humidity, both of which were controlled during the measurement process. The method provides a sensitive real-time analysis of hydrogen sulphide and could be carried out remote from the instrumentation system.

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Schwefelwasserstoffbestimmung durch Bleiacetat-imprägniertes Papier mit Hilfe eines optischen Sensors

     

A theoretical study of the condensation reactions of methyl cation with ammonia,water, hydrogen fluoride and hydrogen sulphide

Ab initio molecular orbital calculations have been used to study the condensation reactions of CH₃^? with NH₃, H₂O, HF and H₂S. Geometry optimization has been carried out at the Hartree—Fock (HF) level with the split-valence plus d-polarization 6-31G* basis set and improved relative energies obtained from calculations which employ the split-valence plus dp-polarization 6-31G** basis set with electron correlation incorporated via Moller—Plesset perturbation theory terminated at third order (MP3). Zero-point vibrational energies have also been determined and taken into account in deriving relative energies. The structures of the intermediates CH₃XH^? (X = NH₂, OH, F and SH) have been obtained and dissociation of these intermediates into CH₂X⁺ + H₂ on the one hand, and CH₃^? + HX on the other, has been examined. It is found that for those species for which the methyl condensation reaction is observed to have an appreciable rate (X = NH₂ and SH), the transition structure for hydrogen elimination from CH₃XH^? lies significantly lower in energy than the reactants CH₃^? + HX (by 75 and 70 kJ mol^?1 respectively). On the other hand, for those species for which the methyl condensation reaction is not observed (X = OH and F), the transition structure for H₂ elimination lies higher in energy than CH₃^? + HX (by 6 and 87 kJ mol^?1 respectively).     

Differential-pulse polarographic determination of sulphate after reduction to hydrogen sulphide

Sulphate (0–80 μg) is reduced by heating with a mixture of hydriodic acid, formic acid and red phosphorus, the gas is swept by nitrogen into 1 M sodium hydroxide and sulphide is quantified by differential pulse polarography from the peak at –0.76 V vs. Ag/AgCl. None of the ions investigated interfered except those capable of reduction to hydrogen sulphide.