Sulfur Trioxide1

Sulfur trioxide

Sulfur trioxide;Sulfur oxide (SO3);Sulfuric anhydride;Nisso Sulfan;856577-62-3

7446-11-9

O3S

InChIKey=AKEJUJNQAAGONA-UHFFFAOYSA-N

80.06

80.06

231-197-3

HH2O7V4LYD

1202

1829

DTXSID1029673

White needles|Asbestos-like needles|Pure sulfur trioxide is a colorless liquid that fumes in air at room temperature and pressure.

Coating Additive

83.30000

0.29180

Sulfur trioxide, is a colorless to white crystalline solid which will fume in air. Often shipped with inhibitor to prevent polymerization. It reacts violently with water to form sulfuric acid with the release of heat. It is corrosive to metals and tissue. It causes eye and skin burns. Ingestion causes severe burns of mouth esophagus and stomach. The vapor is very toxic by inhalation. It is a fire risk when in contact with organic materials such as wood, cotton, fiberboard, etc.

1.9 g/cm³

16.8 °C

45 °C

H2O: reacts violently

Indoors

280 mm Hg ( 25 °C)

2.8 (vs air)

Inhalation-Human TCL0: 30 mg/m3; Inhalation-Guinea Pig LC50: 50 mg/m3

Combustible in case of organic matter

Heating of high melting sulfur trioxide in glass vessels should be avoided to prevent possible shattering of the container.[The Merck Index, Fourteenth Edition (2006)

Reacts with water|Physical form: colorless solid or liquid; melting point: 16.8 °C; boiling point: 44.5 °C; density: 1.90 g/cu cm; reacts with water /gamma-form/|Physical form: white needles; melting point: 30.5 °C; boiling point: 44.5 °C; reacts with water /beta-form/|Sulfur trioxide can exist in both monomeric and polymeric forms. In the gaseous and liquid state, pure SO3 is an equilibrium mixture of monomeric SO3 and trimeric S3O9, also called Y-SO3.|Traces of moisture ... cause liquid SO3 to polymerize first to a low melting, asbestos-like form, beta-SO3 /which/ forms crystal with a silky luster. Additional reaction involves cross-linking of beta-SO3 to form a high melting, asbestos-like form, alpha-SO3 ... crystals resemble ice needles. An additional form has been mentioned ... as vaselinartiges ie, vaseline-like or gelatinous|Critical volume: 127 cu cm/mol|Heat of fusion: 8.60 kJ/mol /gamma-form/|Dielectric constant: 3.11 at 291.2 K|Melted sulfur trioxide exists in the gamma-form and on solidifying tends to the alpha form. The difference in vapor pressures explains the so-called "alpha explosion" of sulfur trioxide. Absolutely dry sulfur trioxide shows no acid reaction.|For more Other Experimental Properties (Complete) data for Sulfur trioxide (11 total), please visit the HSDB record page.|Physical form: ice-like mass; melting point: 16.8 °C or liquid; density: 1.9224; boiling point: 44.8 °C at 760 mm Hg; vapor pressure: 433 mm Hg at 25 °C /gamma-form/|Oxidizing agent, fire risk in contact with organic materials, an explosive increase in vapor pressure occurs when the alpha-form melts.

Combines with water with explosive force, forming sulfuric acid. Sulfur trioxide chars most organic substances. On exposure to air it absorbs moisture rapidly, emitting dense white acidic fumes, mists [Merck 11th ed. 1989].

Acids, Strong Oxidizing

Strong Oxidizing Agent

The reaction of SULFUR TRIOXIDE and oxygen difluoride is very vigorous and explosions occur if the reaction is carried out in the absence of a solvent [J. Chem. Eng. Data 13(4):529-531. 1968]. The reaction of sulfur trioxide in excess with tetrafluoroethylene causes explosive decomposition to carbonyl fluoride and sulfur dioxide [Chem. Eng. News 49(22):3. 1971]. The reaction of anhydrous perchloric acid with sulfur trioxide is violent and accompanied by the evolution of considerable heat (Pascal 16:300 1931-34). Liquid sulfur trioxide reacts violently with nitryl chloride, even at 75° C. The reaction of sulfur trioxide and lead oxide causes white luminescence [Mellor 7:654 1946-47]. The combination of iodine, pyridine, sulfur trioxide, and formamide developed a gas over pressurization after several months. This is due to the slow formation of sulfuric acid, from external water or dehydration of the formamide to hydrogen cyanide.

The vapour is heavier than air.

Absolute dry sulfur trioxide is not corrosive to metals

43.14 kJ/mol at 25 °C

Critical temperature: 491.0 K; critical pressure: 8.2 Mpa