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Sulfur trioxide

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Sulfur trioxide Basic information
Sulfur trioxide Chemical Properties
  • Melting point:16.8 °C(lit.)
  • Boiling point:44.8 °C
  • Density 1.97 g/mL at 25 °C(lit.)
  • vapor density 2.8 (vs air)
  • vapor pressure 280 mm Hg ( 25 °C)
  • storage temp. Indoors
  • form colorless liquid
  • Water Solubility reacts violently
  • Merck 13,9069
  • Stability:Stable. Incompatible with organic materials, finely powdered metals, bases, water, cyanides and a wide variety of other chemicals. Reacts violently with water, oxygen and other chemicals - read a full data sheet before use.
  • CAS DataBase Reference7446-11-9(CAS DataBase Reference)
  • NIST Chemistry ReferenceSulfur trioxide(7446-11-9)
  • EPA Substance Registry SystemSulfur trioxide(7446-11-9)
Safety Information
Sulfur trioxide Usage And Synthesis
  • Chemical PropertiesSulfur trioxide, S03, also known as sulfuric anhydride, needles or polymer, exists in a number of modifications that differ in molecular species and crystalline form. It has a white,ice-like modification that melts at 16°C (61°F) and two other as bestos-like forms that melt at the higher temperatures of 33 and 62°C (90 and 144 °F). The colorless liquid or gas form has irritating, toxic fumes and boils at 45 °C (112 °F). Sulfur trioxide is a highly reactive substance, a strong oxidizing agent,and a fire hazard. It reacts with metallic oxides to form sulfates and with water to form sulfuric acid. Sulfur trioxide is used for sulfonation.
  • Chemical PropertiesSulfur trioxide is a crystalline solid which has 3 forms: alpha-, beta-, and gamma-; and can also exist as a gas or liquid.
  • UsesSulfonation of organic compounds, especially nonionic detergents, solar energy collectors. It is usually generated in the plant where it is to be used.
  • General DescriptionSulfur trioxide, is a colorless to white crystalline solid which will fume in air. Often shipped with inhibitor to prevent polymerization. Sulfur trioxide reacts violently with water to form sulfuric acid with the release of heat. Sulfur trioxide is corrosive to metals and tissue. Sulfur trioxide causes eye and skin burns. Ingestion causes severe burns of mouth esophagus and stomach. The vapor is very toxic by inhalation. Sulfur trioxide is a fire risk when in contact with organic materials such as wood, cotton, fiberboard, etc.
  • Air & Water ReactionsCombines with water with explosive force, forming sulfuric acid due to its acidity Sulfur trioxide chars most organic substances. On exposure to air Sulfur trioxide absorbs moisture rapidly, emitting dense white fumes [Merck 11th ed. 1989].
  • Reactivity ProfileThe 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.
  • HazardOxidizing agent, fire risk in contact with organic materials, an explosive increase in vapor pressure occurs when the α form melts. The anhydride combines with water, forming sulfuric acid and evolving heat. Highly toxic, strong irritant to tissue.
  • Health HazardSulfur trioxide is highly toxic. It is an irritant and corrosive to mucous membranes. Poisonous if inhaled or swallowed. Contact causes severe burns to skin and eyes.
  • Fire HazardFire risk in contact with organic materials. An explosive increase in vapor pressure occurs when the alpha form melts. Combines with water with explosive violence, forming sulfuric acid. May ignite other combustible materials (wood, paper, oil, etc.). Flammable poisonous gases may accumulate in tanks and hopper cars. Runoff to sewer may create fire or explosion hazard. Forms sulfuric acid on contact with water. Avoid water and organic materials. On exposure to air, Sulfur trioxide absorbs moisture and emits dense white fumes.
  • Safety ProfilePoison by inhalation. Human systemic effects by inhalation: cough and other pulmonary and olfactory changes. A corrosive irritant to skin, eyes, and mucous membranes. Violent reaction with O2F2, PbO, NClO2, HClO4, P, tetrafluorethylene, acetonitrile, sulfuric acid, dimethyl sulfoxide, dioxan, water, diphenylmercury, formamide, iodine, pyridine, metal oxides. Reacts with steam to form corrosive, toxic fumes of sulfuric acid. When heated to decomposition it emits toxic fumes of SO,. See also SULFURIC ACID.
  • Potential ExposureSulfur trioxide is used as a sulfating and sulfonating agent for detergent, lubricating oil additives, and other organic compounds; in solar energy collectors. It is also used as an intermediate in sulfuric acid manufacture and in making explosives.
  • First aidIf this chemical gets into the eyes, remove any contact lenses at once and irrigate immediately for at least 30 minutes, occasionally lifting upper and lower lids. Seek medical attention immediately. If this chemical contacts the skin, remove contaminated clothing and wash immediately with soap and water. Seek medical attention immediately. If this chemical has been inhaled, remove from exposure, begin rescue breathing (using universal precautions, including resuscitation mask) if breathing has stopped and CPR if heart action has stopped. Transfer promptly to a medical facility. When this chemical has been swallowed, get medical attention. If victim is conscious, administer water, or milk. Do not induce vomiting. Medical observation is recommended for 24 to 48 hours after breathing overexposure, as pulmonary edema may be delayed. As first aid for pulmonary edema, a doctor or authorized paramedic may consider administering a drug or other inhalation therapy.
  • ShippingUN1829 Sulfur trioxide, stabilized, Hazard class: 8; Labels: 8-Corrosive material, 6.1-Poisonous Inhalation Hazard, Inhalation Hazard Zone B.
  • IncompatibilitiesCombustible and Corrosive. A strong oxidizer. Reacts violently with water, steam or moisture, releasing corrosive hydrosulfuric acid. Violent reactions occur on contact with strong bases; strong acids, chemically active metals; reducing agents; finely divided metal; cyanides, nitrates, picrates, fulminates, chlorates, sulfides, carbides, phosphorus, dioxygen difluoride, barium oxide; lead oxide; diphenyl mercury; alcohols, nitryl chloride; acetonitrile, dioxane, tetrafluoroethylene.
  • Waste DisposalReturn refillable compressed gas cylinders to supplier. Nonrefillable cylinders should be disposed of in accordance with local, state and federal regulations. Allow remaining gas to vent slowly into atmosphere in an unconfined area or exhaust hood. Refillabletype cylinders should be returned to original supplier with any valve caps and outlet plugs secured and valve protection caps in place.
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