7783-79-1

Usage

Uses

Used in Electric Industry:
Selenium hexafluoride is used as a gaseous electric insulator for its excellent insulating properties. It is commonly prepared by passing gaseous fluorine over finely divided selenium in a copper vessel.
Used in Semiconductor Industry:
Selenium hexafluoride is used in the production of arc light electrodes, electric rectifiers, and semiconductors due to its high insulation capabilities and stability.
Physical Properties:
Selenium hexafluoride is a colorless gas with a refractive index of 1.895. It has a density of 3.25 g/L at -28°C and liquefies at -34.5°C. The gas freezes at -50.8°C and sublimes at -63.8°C. It is insoluble in water.

Preparation

Selenium hexafluoride is prepared by passing fluorine gas over finely divided selenium in a copper vessel:Se + 3F2 → SeF6.

Air & Water Reactions

Insoluble in water.

Reactivity Profile

SELENIUM HEXAFLUORIDE is a colorless, poison gas, when heated to decomposition SELENIUM HEXAFLUORIDE emits very toxic fumes containing metallic selenium and selenium fluorides [Lewis, 3rd ed., 1993, p. 1131].

Safety Profile

Poison by inhalation. When heated to decomposition it emits very toxic fumes of Fand Se. See also SELENIUM COMPOUNDS and FLUORIDES.

Potential Exposure

Selenium hexafluoride, a gas, is utilized as a gaseous electric insulator.

Shipping

Selenium hexafluoride, Hazard Class: 2.3; Labels: 2.3-Poisonous gas, 8-Corrosive material Inhalation, Hazard Zone A. Cylinders must be transported in a secure upright position, in a well-ventilated truck. Protect cylinder and labels from physical damage. The owner of the compressed gas cylinder is the only entity allowed by federal law (49CFR) to transport and refill them. It is a violation of transportation regulations to refill compressed gas cylinders without the express written permission of the owner.

Incompatibilities

Hydrolyzes very slowly in cold water. Decomposes on heating, producing hydrogen fluoride, fluoride, and selenium. Contact with metal or acid will produce toxic gaseous hydrogen selenide.

Waste Disposal

Return refillable compressed gas cylinders to supplier. If possible, convert selenium compounds to an insoluble form with SO2 before landfill or solidification.

InChI:InChI=1/F6Se/c1-7(2,3,4,5)6

Upstream product

• 7782-49-2 selenium 
• 13847-65-9 trifluoroamine oxide 
• 12067-46-8 tungsten diselenide 
• 7782-41-4 fluorine 
• 12058-18-3 molybdenum selenide 

Downstream Products

• 7782-82-3 sodium hydrogen selenite 
• 7782-49-2 selenium 
• 7757-82-6 sodium sulfate 

Relevant academic research and scientific papers

Standard molar enthalpies of formation and transition at the temperature 298.15 K and other thermodynamic properties of the crystalline and vitreous forms of arsenic sesquiselenide (As2Se3). Dissociation enthalpies of As-Se bonds

Fluorine-combustion calorimetry was used to determine the standard molar enthalpies of formation (at the temperature 298.15 K and with standard pressure po = 101.325 kPa) of the crystalline and vitreous forms of arsenic sesquiselenide.The following results were obtained: ΔfHmo(As2Se3, cr) = -(86.1 +/- 4.1) kJmol-1 and ΔfHmo(As2Se3, vit) = -(58.1 +/- 4.2) kJmol-1.The enthalpy of the transition from the vitreous to the crystalline forms of As2Se3, -(28.0 +/- 3.9) kJmol-1 at 298.15 K, is consistent with two of several published values for th e enthalpy of fusion of the crystalline sesquiselenide.The present results have been combined with enthalpy increments and the standard entropy has been recalculated from the literature to give, for As2Se3(cr) only, ΔfHmo and the standard molar Gibbs energy of formation ΔfGmo as functions of temperature.Mean bond enthalpies have been deduced for As4Se3(g) and As4Se4(g) on the basis of the new ΔfHmo values, and the thermodynamic results are shown to be consistent with a linear structure for As2Se2(g) with a central As-As bond.Bond dissociation enthalpies Dmo(As-X) are given, where X = O, S, Se, and Te.

Thermochemistry of germanium monoselenide, and the Ge-Se bond dissociation enthalpy

The standard molar enthalpy of formation ΔfH0m of GeSe(cr) has been determined by fluorine-combustion calorimetry to be -(51.4 +/- 1.5) kJ * mol-1 at T = 298.15 K and p0 = 101.325 kPa.Combination of t

Standard molar enthalpy of formation by fluorine-combustion calorimetry of tungsten diselenide (WSe2). Thermodynamics of the high-temperature vaporization of WSe2. Revised value of the standard molar enthalpy of formation of molybdenite (MoS2)

A high-purity sample of WSe2, containing in total mass fraction less than 1 x 10-4 of oxygen and other impurities, has been synthesized by combination of the elements.The standard specific energy of combustion of pure WSe2 in fluorine, as measured by high-precision calorimetry, is -(10993.7+/-15.0) J*g-1, and the derived standard molar enthalpy of formation ΔfHm0 is -(185.3+/-5.5) kJ*mol-1 at T = 298.15 K and p0 = 0.101325 MPa.This result is compared with other literature values, and the equilibrium partial pressures of Se2(g) and Se(g) are estimated for decomposition of WSe2 to and 1/2WSe2 to .Our published result (J.Chem.Thermodynamics 1970, 2, 797) for ΔfHm0(MoS2) at 298.15 K has been revised to -(271.8+/-4.9) kJ*mol-1.

A fluorine-combustion calorimetric study of two molybdenum selenides: MoSe2 and Mo6Se6

Combustion calorimetric measurements of the energies of fluorination of molybdenum selenides have yielded the following standard molar enthalpies of formation at 298.15 K and p0 = 101.325 kPa: ΔfHm0(MoSe2, cr) = -(234.2+/-3.3) kJ * mol-1 and ΔfHm0(Mo6Se6, cr) = -(477.8+/-10.0) kJ * mol-1.The dissociation enthalpy for the reaction: MoSe2(cr) = Mo(cr) + Se2(g), is (378.3+/-3.4) kJ * mol-1 at 298.15 K.A brief discussion is included of the thermodynamics of dissociation of the molybdenum dichalcogenides.