The Chromatographic Analysis of Reduced Sulfur Gases in Antarctic Waters Following Pre-Concentration onto Tenax

Abstract

A technique was developed using sparging and pre-concentration onto a Tenax trap at ambient temperature allowing field measurements to be made of reduced sulfur gases in Antarctic marine and glacial melt waters. Following thermal desorption, gases were determined by gas chromatography using a flame photometric detector. Detection limits in ng 1^?1 were: H₂S 50, OCS 8, SO₂ 160, CH₃SH 6, CH₃SCH₃ 20 and CS₂ 2. Storage of melt water samples for more than 24 hours resulted in concentration changes of the reduced sulfur gases present. While the Antarctic environment imposed limitations on the analytical method, an investigation of various pond and marine waters was undertaken.     

Infrared Emission of Air Pollutants Induced by a CO2 Laser

Abstract

A possible method for the measurement of air pollutants is described. It is based on infrared emission from gases at specific wavelengths induced by a CO₂ laser. The emission level can be increased by adding a sensitizing gas (e.g. SF.) to the sample gas. Although the mechanism of the emission is not fully understood experimental data indicate that the emission is of thermal origin. Spectra of some air polluting gases are included in this paper.     

The Sampling and Gas Chromato-graphic Analysis of Fatty Acids from Landfill Sites

Abstract

A gas chromatographic technique has been developed and applied to the qualitative and quantitative analysis of fatty acids in the interstitial gases of landfill sites. Acetic, propionic. and butyric acids were those shown to be present in the highest concentrations. The fatty acid concentrations were higher at a site where landfill had been completed two years ago than at a site where operations had finished twenty-five years ago.

The concentrations of fatty acids measured were well above the odour thresholds. These compounds may be responsible for the unpleasant smells frequently associated with landfill gases.     

Dew Points of Binary Nitrogen + Water Mixtures

Abstract

Experimental measurements of dew point for binary nitrogen + water were carried out between 5.010⁵Pa and 100.210⁵ Pa and temperatures from 263.0 K to 283.7 K. The experimental method is based on the generation of wet gases by water condensation in two temperature-controlled condensers with continuous gas flow at specified pressures.     

Gas‐Constructed Vesicles with Gas‐Moldable Membrane Architectures

Integrating gas as a main building block into nanomaterial construction is a challenging mission that remains elusive. Herein, we report a gas‐constructed vesicular system formed by CO₂ gas and frustrated Lewis pairs (FLPs). Two molecular triads bearing three bulky borane and phosphine groups are designed as trivalent disc‐like FLP monomers. CO₂, as a gas cross‐linker, can drive the two‐dimensional polymerization of these two FLP monomers, leading to the generation of planar FLP networks that further transform into a thermodynamically favored membranous vesicle structure. Gas‐guided vesicle formation is also applicable to other inert but FLP‐activatable gases. Different gas linkages can form vesicles with distinct architectures, sizes, and morphologies. We envisage that this study would suggest a new concept that exploits gases to fabricate tunable nanomaterials.     

Occurrence of Volatile Metal and Metalloid Species in Landfill and Sewage Gases

Abstract

Speciation of volatile metals and metalloids in the environment is extensively described in literature. In order to investigate unstable volatile organometallics, on-line coupling of GC with ICP-MS was used. Preliminary results for gases of sewage sludge fermentation at thermophilic and mesophilic conditions are compared with the metal and metalloid speciation in landfill gases. In each case 20 L gas were sampled by cryogenic trapping. The species were identified by element-specific detection either by retention time of standards or by calculation of the boiling point correlation. Characteristic of the separation is the linear correlation of boiling point (bp/°C) versus retention time (rt/min) (bp = 6.39?rt -109.2, r² = 0.9926). The amounts of total volatile elements are estimated by semi-quantification. Cd, Sn. Hg, Pb (sewage gas) and Se, Te, Hg, Pb (landfill gas) were determined in the range of ng m^?3 level; As, Sb, Te and Bi (sewage gas) and As, Sn, Sb and Bi (landfill gas) in the μg m^?3 level range.     

Gas-Constructed Vesicles with Gas-Moldable Membrane Architectures

Integrating gas as a main building block into nanomaterial construction is a challenging mission that remains elusive. Herein, we report a gas-constructed vesicular system formed by CO₂ gas and frustrated Lewis pairs (FLPs). Two molecular triads bearing three bulky borane and phosphine groups are designed as trivalent disc-like FLP monomers. CO₂, as a gas cross-linker, can drive the two-dimensional polymerization of these two FLP monomers, leading to the generation of planar FLP networks that further transform into a thermodynamically favored membranous vesicle structure. Gas-guided vesicle formation is also applicable to other inert but FLP-activatable gases. Different gas linkages can form vesicles with distinct architectures, sizes, and morphologies. We envisage that this study would suggest a new concept that exploits gases to fabricate tunable nanomaterials.     

Nonequilibrium Flow and the Kinetics of Chemical Reactions in the Char Zone

Abstract

In the temperature range of 500–2500°F, nonequilibrium flow analysis predicted only a small change in pyrolysis gas composition as the gases flow through the char zone. Essentially all of the reactions took place in the temperature range of 2000–2500°F. Comparing nonequilibrium flow with the two limiting cases, the energy absorbed in the char zone for frozen flow was two-thirds that of nonequilibrium flow, and equilibrium flow was about four times that of nonequilibrium flow at the 2500°F level.     

Simultaneous Determination of C,S, Cl,Br, and I in Organic Compounds by Gas Chromatography

Abstract

A procedure is described for the simultaneous determination of C, S, Cl, Br and I in organic compounds by gas chromatography. Combustion of the sample to CO₂, SO₂ Cl₂, Br₂ and I₂ is effected, followed by a separation of the gases on two 10 ft. Al columns containing Kel F-3 and either Aroclor or dioctylphthalate.     

Application of an Electrostatic Precipitator for Instrumental Sampling of Sulfuric Acid

Abstract

A means of separating gaseous sulfuric acid from flue gas particles has been evaluated. Previous attempts to achieve this separation by filtration resulted in retention of the acid by the particulate buildup on the filter surface. By conducting a laboratory study of a prototype electrostatic precipitator, followed by actual flue gas sampling, it was found that the precipitator may eliminate the need for a filter without affecting the measurement results. It was also found that the precipitator could be used prior to a prototype acid monitor for the successful continual monitoring of H₂S0₄ in combustion gases.     

Hydrate capture CO2 from shifted synthesis gas,flue gas and sour natural gas or biogas

CO₂ capture by hydrate formation is a novel gas separation technology, by which CO₂ is selectively engaged in the cages of hydrate and is separated with other gases, based on the differences of phase equilibrium for CO₂ and other gases. However, rigorous temperature and pressure, high energy cost and industrialized hydration separator dragged the development of the hydrate based CO₂ capture. In this paper, the key problems in CO₂ capture from the different sources such as shifted synthesis gas, flue gas and sour natural gas or biogas were analyzed. For shifted synthesis gas and flue gas, its high energy consumption is the barrier, and for the sour natural gas or biogas (CO₂/CH₄ system), the bottleneck is how to enhance the selectivity of CO₂ hydration. For these gases, scale-up is the main difficulty. Also, this paper explored the possibility of separating different gases by selective hydrate formation and reviewed the progress of CO₂ separation from shifted synthesis gas, flue gas and sour natural gas or biogas.     

Automatic Carbon,Hydrogen, Nitrogen,Sulfur Analyzer Ciiemistry of Sulfur Reactions

Abstract

An automatic analyzer for the simultaneous microdetermination of carbon, hydrogen, nitrogen, and sulfur is described. The method is based on the uncatalyzed, dynamic, flash-combustion of the sample in an oxygen/helium atmosphere in a quartz tube. Separation of the combustion gases, N₂, CO₂, SO₂, and H₂O is accomplished by using gas chromatography and a thermal conductivity detector. Reactions of SO₂ formation are given in detail.     

New Gas Chromatographic Detection of Nitric Oxide

Abstract

In acetonitrile nitric oxide was made to react with p-chloroaniline in the presence of copper (II) bromide at room temperature. The resulting p-chlorobromobenzene was determined by flame ionization and/or electron capture gas chromatography. The influence of several gases which coexist with nitric oxide on this reaction was investigated briefly.     

Reply to comment on “liquid metal transport properties”

Abstract

The method^1,2 used to determine energy parameters with which to correlate liquid metal transport properties yields relative and not absolute values for these parameters. The choice of a reference substance and its value of E/k is arbitrary. Professor Collings' point is well taken that one might as well use an up-to-date value of E/k for the energy parameter of the reference substance. Nevertheless, one should not expect close agreement values of energy parameters determined from liquid metal viscosity and diffusivity data and values determined from neutron scattering experiments. Preston et a1.² found some disagreement between E/k values obtained from liquid transport data and values obtained from gas viscosity data for the rare gases. The asumption of the validity of the law of corresponding states for liquid metals is certainly more questionable than its applicability to the rare gases.     

Comparison of portable devices for sub-ambient concentration measurements of methane (CH4) and nitrous oxide (N2O) in soil research

ABSTRACT

Production and consumption of methane (CH₄) and nitrous oxide (N₂O) in soils have a strong influence on global greenhouse gases (GHG) budgets. Therefore, it is crucial to precisely measure GHG fluxes at the soil–atmosphere interface. In upland soils, CH₄ and N₂O can be consumed by microbiological processes, and the respective concentrations can be lower than in the atmosphere, demanding highly sensitive gas analysing systems. Traditionally, soil air is sampled in vials and analysed in the laboratory by gas chromatography (GC). During the last decade, different technologies have been developed that allowed to build portable gas analysers that are able to measure sub-ambient gas concentration directly in the field. Here, we compared sub-ambient to ambient CH₄ and N₂O concentration values from four portable devices using different measurement technologies (a portable GHG analyser based on laser absorption spectroscopy [LAS], two portable Fourier transform infrared spectroscopy [FTIR] devices and a field gas analyser using photoacoustic spectroscopy [PAS]) to traditional GC analysis in the laboratory (a GC system equipped with a flame ionisation detector [GC-FID] and an electron capture detector [GC-ECD]). The accuracy and precision of photoacoustic spectroscopy measurements are strongly influenced by the water vapour content and non-target gases in the sampling air. We used an advanced set-up for a widely used PAS analyser enabling N₂O measurements at sub-ambient concentrations with similar precision and accuracy as the GC-ECD system. Measurements of CH₄ and N₂O by FTIR and LAS devices were in good agreement with the GC systems. We conclude that the portable devices are suitable for studies of GHG fluxes in the field. Thanks to their universal and portable character, LAS, PAS and FTIR devices represent useful alternatives to currently used technologies for field studies.     

H2S gas sensor based on integrated resonant dual-microcantilevers with high sensitivity and identification capability

Detection of trace-level hydrogen sulfide (H₂S) gas is of great importance whether in industrial production or disease diagnosis. This research presents a novel H₂S gas sensor based on integrated resonant dual-microcantilevers which can identify and detect trace-level H₂S in real-time. The sensor consists of two integrated resonant microcantilever sensors with different functions. One cantilever sensor can identify H₂S by outputting positive frequency shift signals, while the other cantilever sensor will detect H₂S as a normally used cantilever sensor with negative frequency shifts. Combined the two cantilever sensors, the proposed gas sensor can distinguish H₂S from a variety of common gases, and the detection limit to H₂S of the sensor is as sensitive as below 1 ppb.     

Gas chromatographic determination of admixtures of permanent gases, CO, CO2, and hydrocarbons in methylsilane

A procedure is developed for the gas chromatographic determination of admixtures of permanent gases, CO, CO₂, and hydrocarbons in methylsilane with detection limits of 0.02–0.8 ppm. The procedure was applied to the analysis of methylsilane obtained by reducing methyltrichlorosilane with sodium tetrahydrob-orate in an organic solvent. Admixtures of permanent gases and C₁–C₅ hydrocarbons the in synthesized methylsilane were detected.     

Dissociation enthalpies and phase equilibrium for TBAB semi-clathrate hydrates of N<Subscript>2</Subscript>, CO<Subscript>2</Subscript>, N<Subscript>2</Subscript> + CO<Subscript>2</Subscript> and CH<Subscript>4</Subscript> + CO<Subscript>2</Subscript>

Tetra-n-butyl ammonium bromide (TBAB) semi-clathrate (sc) hydrates of gas are of prime importance in the secondary refrigeration domain and in the separation of gas molecules by molecular size. However, there is a scarcity of dissociation enthalpies under pressure of pure gases and gases mixtures for such systems. In addition, the phase equilibrium of TBAB sc hydrates of several pure gases is not well defined yet as a function of the TBAB concentration and as a function of the pressure. In this paper, dissociation enthalpies and the phase equilibrium of TBAB sc hydrates of gas have been investigated by differential scanning calorimetry (DSC) under pressure. Pure gases such as N₂ and CO₂ and gases mixtures such as N₂ +  CO₂ and CH₄ +  CO₂ were studied. To our knowledge, we present the first phase diagram of TBAB sc hydrates of N₂ for different pressures of gas in the TBAB concentration range from 0.170 to 0.350 wt. Enthalpies of dissociation of TBAB sc hydrates of pure gases and gases mixtures were determined as a function of the presssure for a compound with a congruent melting point whose hydration number corresponds to 26.     

Experimental Parameters Affecting the Intensity of Cadmium Electrodeless Discharge Lamps

Abstract

Several experimental parameters have been found to affect the intensity of microwave excited electrodeless discharge emission at the cadmium resonance line (228.8 nm.). A thorough study of the effect of pressure of the fill gas, microwave power applied to the tube; and weight of Cd introduced into the tube has been accomplished. Direct comparisons of Cd resonance emission for the cases of He, Ne, Ar and air fill gases are presented. From these studies preductions of optimum conditions for construction and operation of Cd electrodeless discharge lamps may be made.     

Determination of the Concentration of Gases by Measurement of Pressure

Abstract

For the determination of the concentration of gases by means of pressure measurement, a precise equation of state is given by which analysis can be carried out within an accuracy of 10 ppm. The parameters of the equation of state are explicitely reported for carbon dioxide, argon, and helium.