Sulfur hexafluoride values

Sulfur trioxide gas reacts with gaseous hydrogen fluoride to produce gaseous sulfur hexafluoride and water vapour. The value of Kc is 6.3 X 10 3. 

Secondary windings connected in series feed the high-voltage terminal. The system provides a beam only during the negative half cycle, with a voltage variation between zero and the peak value the machine was designed to deliver. Sulfur hexafluoride gas is used for electrical insulation. ... 

For a coulometric response, an ideal compound, sulfur hexafluoride, has remarkable sensitivity (10-1 g/sec). Again it should be emphasized that this value will be unique for a particular compound and depends on the species affinity for electron capture. 

Some measurements have been made of self diffusion in pure ethylene and in ethylene-sulfur hexafluoride mixtures (22), but these measurements were made very close to the critical temperature and up to pressures of only about 100 bar. Proton spin-lattice relaxation times (T.) of ethylene have been measured at temperatures from 0°C to 50°C and pressures up to about 2300 bar (13). The relaxation time values were -M0—50 sec for much of the region studied. Several relaxation mechanisms contribute to this long relaxation time and make both the measurement and analysis of the relaxation times very difficult. For these reasons, we decided to limit our study to the measurement of the self-diffusion coefficient in supercritical ethylene (60. 

Calculate Z and V for sulfur hexafluoride at 100°C and 15 bar by the following equations (a) The truncated virial equation (3.33) with the following experimental values of virial coefficients ... 

Maiwald and Schneider134 studied the probe pair 8/7 in order to examine the EPD/HBA abilities of supercritical chlorotrifluoromethane, sulfur hexafluoride, dinitrogen oxide and SCCD and found, as expected, that none of these had such abilities (i.e. fi 0). On the contrary, supercritical ammonia had appreciable fi values (0.70 at 293 K and 100 MPa), being moderately temperature dependent but with little change on lowering the pressure. 

Elements with high values of E are present as anions in compounds with metallic elements and commonly have negative oxidation states in covalent compounds with other nonmetallic elements. For example, F has an oxidation state of-I in sulfur hexafluoride, SF6. 

The oxidation number of sulfur in sulfur hexafluoride attains its maximum value of +6, but the large number of strongly electronegative fluorine atoms around the sulfur atom protects the compound from attack. Because it has a high ionization energy, sulfur hexafluoride is a good gas phase electrical insulator. 

Figure 4.5 Negative-ion mass spectrometry data plotted as In KT312 versus 1,000/7 for nitrobenzene and sulfur hexafluoride. The data exhibit one a and one P region. The magnitude was scaled to the value of the k for SF6 at room temperature. The curves are calculated using the measured electron affinities of SFg and C6H5NC>2. The data determine the Qan values to he 1.0. The responses were obtained by injecting a solution with a known amount of the two compounds into the mass spectrometer.

Figure 5.15 Timeline for the electron affinities of sulfur hexafluoride. The lower values can be assigned to excited states. The one higher value is known to have a larger random uncertainty.

Electron affinity of sulfur hexafluoride was studied using various density functionals and systematically expanded basis sets with polarization function exponents optimized in molecular environment, /-type polarization functions were found necessary to ensure convergence of both geometry and electron affinity. The ion was found to have octahedral symmetry, and the smallest value of electron affinity is only 1.40 eV (1.6 eV with zero-point energy correction). 

Physical properties of sulfur hexafluoride are listed in Table I. These include various values of the critical constants. Several excellent studies of the critical phenomena have been made to learn whether the predictions of Harrison and Mayer (125) are correct. They suggested in 1938 that there could be a range of temperature above the observed critical point (disappearance of meniscus) in which the slope of pressure versus volume isotherms is zero. Their arguments have been criticized by Zimin (334) in... 

Other volatile tracers have been used in estuaries to determine gas exchange coefficients. These tracers, such as chlorofluorocarbons (CFCs) or sulfur hexafluoride (SFg), are synthetic compounds with no known natural source. Unlike Rn, these gases are stable in solution. These tracers may be added to the aquatic system and the decrease of the gas due to flux across the air/water interface monitored over time. In some estuaries, point sources of these compounds may exist and the decrease of the tracer with distance downstream may be used to determine k or z values for the estuary. 

To illustrate how these equations are applied, we repeat the calculations in 5.3.1 to obtain excess properties for gaseous mixtures of methane and sulfur hexafluoride at 60°C, 20 bar. Values for the isometric residual properties of this mixture have already been determined in 4.5.5. We continue to use the virial equation of state (5.3.2), but now we write it in a pressure-explicit form. 

The standard molar volume of an ideal gas is 22.414 liters per mole at STP. However, the standard molar volume of a gas that has a high molecular weight or strong intermolecular attractive forces can deviate significantly from this value. Calculate the standard molar volume of sulfur hexafluoride (SFj), density = 6.65 g/L at STP, and hydrogen fluoride (HF), density = 0.922 g/L at STP. 

ACGIH recommends a Threshold Limit Value-Time-Weighted Average (TLV-TWA) of 1000 ppm (5970 mg/m ) for sulfur hexafluoride. The TLV-TWA is the time-weighted average concentration for a normal 8-hour workday and a 40-hour workweek, to which nearly all workers may be repeatedly exposed, day after day, without adverse effect [1]. 

Attachment to gaseous sulfur hexafluoride (SF ) at T = 300 K was found to proceed with one of the highest rate constants measured for any compound (Massey, 1979). A value of... 

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