Hydrogen fluoride

We report a detection of the excited 220-211 rotational transition of para-H2O in APM 08279+5255 using the IRAM Plateau de Bure interferometer. At z = 3.91, this is the highest-redshift detection of interstellar water to date. From LVG modeling, we conclude that this transition is predominantly radiatively pumped and on its own does not provide a good estimate of the water abundance. However, additional water transitions are predicted to be detectable in this source, which would lead to an improved excitation model. We also present a sensitive upper limit for the HF J = 1 - 0 absorption toward APM 08279+5255. While the face-on geometry of this source is not favorable for absorption studies, the lack of HF absorption is still puzzling and may be indicative of a lower fluorine abundance at z = 3.91 compared with the Galactic ISM.

In this paper, we present the objectives and features of the payload subsystem of SNSAT, the nanosatellite which is to be launched by SathyabamaUniversity in near future. The payload comprises of the spectrometer and its interface, with the prime aim to detect the concentration of five major constitutes green house gases namely, Carbon Dioxide, Water, Carbon Monoxide, Methane and Hydrogen

This pilot study tested the hypothesis that aluminium (Al), rubidium (Rb), arsenic (As), lead (Pb), mercury (Hg), fluorine (F), and chlorine (Cl), which are all known to be present in volcanic emissions, may be useful biological markers for occupational gas exposure in volcanologists. Ten human subjects were exposed to fumarole gases on White Island, New Zealand, for approximately 20 minutes. Sulphur dioxide (SO2) exposure was recorded by personal monitoring tubes. Pre- and post-exposure urine, blood and serum samples (collected using standard protocols) were analysed in the pathology laboratory for trace element and halogen content. Average personal exposure was measured at <75 ppm SO2 and calculated at approximately 25 ppm HCl, approximately 8 ppm hydrogen fluoride (HF), approximately 1 ppm Al, approximately 0.1 ppb Rb and approximately 4 ppb Pb. These concentrations almost certainly exceed those usually found in occupational exposure settings. Advanced levels of urinary Al and...

We investigate the energetic, structural, electronic and thermodynamics properties of hydrogen fluoride cluster, (HF)n, in the range n=2-8, by ab initio methods and density functional theory (DFT). The ab initio methods chosen were Hartree-Fock (RHF) and second-order Møller-Plesset perturbation theory (MP2). The DFT calculations were based on Becke's hybrid functional and the Lee-Yang-Parr correlation functional (B3LYP). We found that symmetric cyclic clusters are the most stable structure, and that large cooperative effects, particularly from trimer to tetramer are present, in binding energy, and hydrogen bond distance. An analysis of the topology of the electron density reveals a linear correlation between the binding energy per hydrogen bond and the density at the hydrogen bond critical point and the Cioslowski covalent bond order. Based on these correlations, hydrogen bond cooperativity is associated with the electronic delocalization between monomers units. Analysis of the thermodynamics properties shows that the enthalpy changes are determined by the electronic cooperative effects, while the entropic statistical factors are fundamental in the relative stability of these clusters. Finally, for the trimer and tetramer, nonstable linear zigzag chains where found in a detailed analysis of the potential energy surfaces.

MP2/6-31++G(d,p) and B3LYP/6-31++G(d,p) theoretical calculations have been employed to investigate the hydrogen bonding formation involving the vic-, cis- and trans-C 2H 2F 2 isomers and hydrogen fluoride. Our calculations have revealed for each isomer the preferential existence of two possible hydrogen-bonded complexes: a non-cyclic complex and a cyclic complex. For all the three isomers the binding energies for the non-cyclic and cyclic hydrogen complexes are essentially equal using both the MP2 and B3LYP calculations, being that the cyclic structure is slightly more stable. For instance, the binding energies including BSSE and ZPE corrections for the non-cyclic and cyclic structures of cis-C 2H 2F···HF are 8.7 and 9.0 kJ mol -1, respectively, using B3LYP calculations. The cyclic complex formation reduces the polarity, in contrast to what occurs with the non-cyclic complex. This result is more accentuated in vic-C 2H 2F 2···HF. In this latter, Δ μ(cyclic) is -3.07 D, whereas Δ μ(non-cyclic) is +1.92 D using B3LYP calculations. Their corresponding MP2 values are +0.44 D and -1.89 D, respectively. As expected, the complexation produces an H sbnd F stretching frequency downward shift, whereas its IR intensity is enhanced. On the other hand, the vibrational modes of the vic-, cis- and trans-C 2H 2F 2 isomers are little affected by complexation. The new vibrational modes due to hydrogen bonding formation show several interesting features, in particular the HF bending modes which are pure rotations in the free molecule.

ABSTRACT Coating of AZ31B, AE 42 and ZRE1 wrought magnesium alloys was carried out using electroless Ni plating technique in a solution of nickel sulphate, sodium hypophosphite, ammonium hydrogen fluoride and glycine with a zinc immersion pre-treatment.The results of SEM/EDX investigations and X-ray diffraction indicate that the coat exhibit a typical surface morphology with compact nodules with good adherence to the substrate. The coat was composed of amorphous structure, which transformed to a mixture of crystalline Ni and Ni3P precipitates after heat treatment at 673°K for 1 h. The phosphorous (P) content increased gradually from the substrate towards the surface reaching a maximum of 10 wt.% to 18 wt.% on the surface depending on the substrate alloy and the thickness of deposit. The hardness of the coat was found to increase with the P content and also after heat treatment. The electrochemical corrosion test in NaCl solution indicated a great improvement in the corrosion resistance of the Mg substrates and that a noble behaviour of Ni–P was obtained regardless of the heat treatment process. The forming ability test indicates that hot rolling of the coated substrate does not succeed to keep a continuous coat due to cracking of the coat in both as-coated and heat treated specimens.

Collision-induced dissociation (CID) mass spectra of a few haloaniline isomers,(chloroanilines, dichloroanilines, difluoroanilines, chloro-fluoroanilines and bromo-fluoroanilines) were characterized. The mass spectral behaviour of difluoroanilines was ...

Almost half of the total rural area of Guizhou Province and many regions within the 11 adjacent provinces in southwestern China have a long history (at least 70 years) of endemic fluorosis, including dental fluorosis and osteofluorosis along with its associated deformities and disabilities. Over decades of research, this specific type of endemic fluorosis has been defined as coal-burning fluorosis,

Abstract:[en] Hydrogen chloride (HCl) and hydrogen fluoride (HF) are respectively the main chlorine and fluorine reservoirs in the Earth's stratosphere. Their buildup resulted from the intensive use of man-made halogenated source gases, in particular CFC-11 (CCl3F) and ...

In this study we have calculated the threat zones for the oil and gas industries using Hydrogen fluoride to extract petroleum oil and gas, with the help of ALOHA software. One of the most essential part of the loss prevention strategy is Emergency Planning. This is a pre planning to handle any emergency situation suitably and effectively. Emergency planning is an integral part of the overall loss control program and is essential for any organization. The same is vital for effective management of an accident /incident to attenuate losses to people and property, both in and round the facility. The important aspect in emergency management is to stop by technical and organizational measures, the unintentional escape and ignition of hazardous materials like Hydrogen fluoride (HF) and minimize accidents and losses. Not only unrecognized hazardous conditions which could aggravate an emergency situation be discovered, the emergency planning process also brings to light deficiencies such as lack of resources necessary for effective emergency response. Emergency planning also demonstrates the organization’s commitment to the safety of employees and increases the organization’s safety awareness.

The rotational g tensors of hydrogen fluoride, water, ammonia and methane are calculated at their equilibrium geometries with various correlated ab initio methods. Among the methods employed are the second order polarization propagator approximation (SOPPA), which was developed by Jens Oddershede and co-workers, the second order polarization propagator approximation with coupled cluster singles and doubles amplitudes (SOPPA(CCSD)), Møller-Plesset perturbation theory in second (MP2), third (MP3) and fourth order (MP4), the coupled cluster method (CCSD) and finally the multiconfigurational self-consistent field method (MCSCF) in the form of complete (CASSCF) and restricted active space (RASSCF) variant with several different active spaces. The results of calculations with the different methods using two large conventional basis sets are compared.

Masaya volcano (560 m a.s.l.), Nicaragua, resumed its degassing activity in mid-1993 with the continuous emission of SO2 at rates increasing from 600 metric tons (t) day–1 (7.0 kg s–1) in 1995 to 1800 t day–1 (21.0 kg s–1) in 1999. The low-altitude gas plume is typically blown westward by the prevailing wind across the Masaya caldera and Las Sierras highlands, which are at a higher elevation than the gas vent. In this study, the areal distribution of atmospheric SO2 concentrations was monitored within 44 km of the vent with a network of passive samplers. Measured SO2 air concentrations ranged from <2 to 90 ppbv in 1998 and from <2 to 230 ppbv in 1999. The data suggest that the volcanic emissions influenced air quality across a 1,250-km2 area downwind. Local topography exerts a strong control on plume dispersal, and hilltops are particularly prone to fumigation and thus, to high ambient SO2 levels. In a zone 22 km2 in size located within 15 km of the source, the response of vegetation to sustained exposure to high atmospheric dose of volcanic SO2 and HF resulted in a strong reduction in the number of plant communities. A transition zone of somewhat indefinite boundary surrounds the devastated zones and exhibits vegetation damage in the form of leaf injury. In addition to the environmental impacts of the volcanic emissions, both short- and long-term public health hazards may exist in areas most exposed to the plume. The harmful effects of the volcanic emissions on cultivated vegetation could be diminished by using windbreaks made of gas-tolerant trees and shrubs such as Eugenia jambos, Brosimum utile and Clusia rosea. The current gas crisis at Masaya volcano provides an unique opportunity for investigating the atmospheric, environmental and medical impacts of volcanic gases and aerosols.