Sulfur hexafluoride effect

Electrica.1 Properties. The electrical properties of SF stem primarily from its effectiveness as an electron scavenger. To accomplish electrical breakdown in a dielectric gas, primary electrons must gain sufficient energy to generate appreciable numbers of secondary electrons on molecular impact. Sulfur hexafluoride interferes with this process by capturing the primary electrons, resulting in the formation of SF or SF ions and F atoms (29) ... 

Sulfur hexafluoride production, 11 846 Sulfur hexafluoride reactive ion etching, in lotus effect surfaces, 22 120 Sulfuric acid, 24 260, 12 190, 23 563, 669, 754-801... 

Toxicology. Sulfur hexafluoride is an agent of low toxicity at extremely high levels it has a mild effect on the nervous system. 

The results (electrostatic-fit charges based on Hartree-Fock 6-3IG wavefunctions) are ambiguous. Relative to dimethylsulfide as a normal-valent standard , the sulfur in oxygen loses about half an electron, and the sulfur in dimethylsulfone loses 1.7 electrons. This would seem to suggest that dimethylsulfoxide is halfway to being a zwitterion, but that dimethylsulfone is most of the way. Charges on sulfur in sulfur tetrafluoride and sulfur hexafluoride (relative to sulfur difluoride) show more modest effects, in particular for the latter. Overall, it appears that hypervalent molecules possess significant ionic character. 

The electrochemical perfluorination of propane-2-thiol46 gives pcntafluoro(heptafluoro-propan-2-yl)-/.6-sulfane (yield 1.7%), fragmented fluorocarbons (main product octafluoro-propane, 48.6%) and sulfur hexafluoride (38.9%) (electrolyte anhyd HF effective surface area of nickel anodes 770 cm2 voltage 4.7-6.1 V current density 2.6 A dm 2 temperature 8 10 C). 

The great kinetic stability of sulfur hexafluoride 73>74>, like that of carbon tetrafluoride 73>, particularly toward nucleophilic reagents, may be viewed as arising from the presence about the central atom s kernel (and about the kernels of the fluorine atoms) of a nearly complete, protective sheath of electrons with no pockets 52> of sufficient depth (orbitals of sufficiently low energy) to permit effective coordination with the unshared electrons of an entering nucleophile. The possibility remains, however, of attack by electrophilic reagents, e.g., by strong Lewis acids, such as sulfur trioxide 74>. 

Sulfur hexafluoride sublimes at -64 °C to produce a dense gas (6.14 g L-1). Under a pressure of 2 atm, the melting point is -51 °C. The molecule has the expected octahedral structure and a dipole moment of zero. The compound is so inert that it is used as a gaseous insulator, and rats allowed to breathe a mixture of SF6 and oxygen show no ill effects after several hours of exposure. This inertness is a result of the molecule having no vacant bonding site or unshared electron pairs on sulfur to initiate a reaction and the fact that six fluorine atoms shield the sulfur atom from attack. Consequently, there is no low-energy pathway for reactions to occur, and the compound is inert even though many reactions are thermodynamically favored. 

A typical problem of interest at Los Alamos is the solution of the infrared multiple photon excitation dynamics of sulfur hexafluoride. This very problem has been quite popular in the literature in the past few years. (7) The solution of this problem is modeled by a molecular Hamiltonian which explicitly treats the asymmetric stretch ladder of the molecule coupled implicitly to the other molecular degrees of freedom. (See Fig. 12.) We consider the the first seven vibrational states of the mode of SF (6v ) the octahedral symmetry of the SF molecule makes these vibrational levels degenerate, and coupling between vibrational and rotational motion splits these degeneracies slightly. Furthermore, there is a rotational manifold of states associated with each vibrational level. Even to describe the zeroth-order level states of this molecule is itself a fairly complicated problem. Now if we were to include collisions in our model of multiple photon excitation of SF, e wou d have to solve a matrix Bloch equation with a minimum of 84 x 84 elements. Clearly such a problem is beyond our current abilities, so in fact we neglect collisional effects in order to stay with a Schrodinger picture of the excitation dynamics. 

A. D. Buckingham and D. A. Dunmur. Kerr effect in inert gases and sulfur hexafluoride. Trans. Faraday Soc., 64 1776-1783 (1968). 

Routes of air-borne contamination into BFS containers were investigated during a study using Sulfur hexafluoride (SFs) tracer gas. During this experiment, the tracer gas was released at a known concentration into a clean room that housed an aseptic BFS machine. Levels of the tracer gas were then measured within subsequently filled BFS units. The study concluded that the container was effectively protected by the localized air shower. Although not necessarily representative of deposition of microbial contaminants, there also was conclusive evidence of some room air within the BFS containers. The control of environmental contamination within the clean room is therefore important. 

The pharmacokinetics of Sono Vue have been studied in 12 healthy volunteers (aged 20-36 years, seven men), who received two intravenous doses of 0.03 and 0.3 ml/kg in random order (16). Sono Vue was rapidly cleared from the blood, with a half-life of 5-7 minutes. About 40-50% of the dose was eliminated in the expired air during the first minute after injection and 80-90% was eliminated by 11 minutes. Within 90 minutes, sulfur hexafluoride could no longer be detected in the expired air in most cases. There were no adverse effects. 

F8. Frankel, J., and Schneiderman, H. A., The effects of nitrogen, helium, argon, and sulfur hexafluoride on the development of insects. J. CeUuIar Comp. Physiol. 62, 431-457 (1958). 

Initial experiments performed at the INL compared different catalysts, fluids, and operating conditions to determine the effect of SCF on solid acid catalyst alkylation (5). Three sets of studies were performed a catalyst comparison using six different catalysts (i.e., two zeolites, two sulfated metal oxides, and two Nafion catalysts) with methane as a cosolvent an exploration of the effect of varying methane addition on alkylation using a USY zeolite catalyst and a study of the effect of seven cosolvents (i.e., three hydrocarbons, two fluorocarbons, carbon dioxide, and sulfur hexafluoride) at L, ML, NC-L, and SCF conditions on the USY catalyst performance. 

The molecule sulfur hexafluoride (SFA has recently challenged both molecular spectroscopy with its unexpected rotational spectra 29) and electronic structure theories with novel correlation effects (30,31,5). The electronic structure must explain the molecule s high stability, octahedral symmetry, and, most importantly, provide a simple picture of the bonding. At first glance, the traditional chemical models do not appear to be appropriate because sulfur seemingly forms six bonds to fluorines, yet the sulfur s2pA valence configuration allows for at most two covalent bonds. 

Water-Isopropyl Alcohol + Additives. Sulfur Hexafluoride. The effect of SF6 on the hydrogen, methane, and carbon monoxide yields from water-isopropyl alcohol mixtures is shown in Figures 1 and 2. Extrapolation to /p = 0 gives G(H2)W° = 5.5 0.3, G(CH4)W° = 0... 

Using one of these sources we have determined product yields from the radiolysis of cyclohexane and the effects on these yields of adding nitrous oxide, benzene, and sulfur hexafluoride. 

The product yields from the radiolysis of cyclohexane containing benzene, nitrous oxide, and sulfur hexafluoride, with electron pulses at a dose rate of 6 X 1027 e.v./gram sec. and a dose of 7 Mrads, are shown in Figures 4, 5, 6, and 7. Also included in these figures are data of other workers (12, 17) at ca. 1016 e.v./gram sec. with 60Co y-rays. Comparison between the results at the two dose rates shows that the effect of the additives is qualitatively the same. However, there are some differences in the amounts by which the yields change. 

Cyclohexane and SF . Sulfur hexafluoride reacts rapidly with electrons, and its effect on the hydrogen, cyclohexene, and bicyclohexyl yields has been explained (12) by the replacement of Reaction lb by Reactions 14 and 15. 

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