Sulfur trioxide

  • Sulfuric anhydride
Formula
SO3
Structure
Description
A colorless to white crystalline solid.
Uses
Intermediate in sulfuric acid manufacture, in sulfonations for formation of addition compound with amines, in the manufacture of explosives.

Registry Numbers and Inventories.
CAS
7446-11-9
EC (EINECS/ELINCS)
231-197-3
RTECS
WT4830000
RTECS class
Tumorigen; Human Data
UN (DOT)
1829
Merck
12,9152
Beilstein/Gmelin
1448 (G)
Swiss Giftliste 1
G-2878
Canada DSL/NDSL
DSL
US TSCA
Listed
Austrailia AICS
Listed
New Zealand
Listed
Japan ENCS (MITI)
Listed
Korea ECL
Listed

Properties.
Formula
O3S
Formula mass
80.05
Melting point, °C
17.7
Boiling point, °C
44.8
Vapor pressure, mmHg
643.7 (41.4 C)
Vapor density (air=1)
2.76
Critical temperature
217.8
Density
1.97 g/cm3 (20 C)
Solubility in water
Reacts
Viscosity
1.59 cP 30 C
Thermal expansion
0.000676/K

Hazards and Protection.
Storage
Keep container closed when not in use. Store in a cool, dry, well-ventilated area away from incompatible substances. Store at around 20 C.
Handling
Wash thoroughly after handling. Do not get in eyes, on skin, or on clothing. Keep container tightly closed. Do not ingest or inhale. Use with adequate ventilation. Wash clothing before reuse. Discard contaminated shoes.
Protection
Eyes: Wear appropriate protective eyeglasses or chemical safety goggles as described by OSHA's eye and face protection regulations in 29 CFR 1910.133 or European Standard EN166. Skin: Wear appropriate protective gloves to prevent skin exposure. Clothing: Wear appropriate protective clothing to prevent skin exposure.
Respirators
A respiratory protection program that meets OSHA's 29 CFR 1910.134 and ANSI Z88.2 requirements or European Standard EN 149 must be followed whenever workplace conditions warrant a respirator's use.
Small spills/leaks
Absorb spill with inert material, (e.g., dry sand or earth), then place into a chemical waste container. Avoid runoff into storm sewers and ditches which lead to waterways. Clean up spills immediately, using the appropriate protective equipment. Provide ventilation. Use water spray to reduce vapors, do not put water directly on leak, spill area or inside container.
Stability
Stable under normal temperatures and pressures.
Incompatibilities
Chlorates, lead oxide, nitrates, cyanides (e.g. potassium cyanide, sodium cyanide), sulfides (inorganic, e.g. ferric sulfide, lead sulfide, sodium sulfide), carbides, diphenylmercury, fulminates, picrates, dioxygen difluoride, white phosphorus, nitryl chloride, barium oxide.
Decomposition
Oxides of sulfur.

Fire.
Fire fighting
Wear a self-contained breathing apparatus in pressure-demand, MSHA/NIOSH (approved or equivalent), and full protective gear. Material will not burn. During a fire, irritating and highly toxic gases may be generated by thermal decomposition or combustion. Reacts with steam to form corrosive, toxic fumes of sulfuric acid. Extinguishing media: Do NOT use water directly on fire. Do NOT get water inside containers. Cool containers with flooding quantities of water until well after fire is out. In case of fire, use carbon dioxide, dry chemical, or water fog.
Fire potential
May burn but does not ignite readily.
Hazards
May ignite combustibles (wood, paper, oil, clothing, etc.). Substance will react with water (some violently), releasing corrosive and/or toxic gases. Flammable/toxic gases may accumulate in confined areas (basement, tanks, hopper/tank cars, etc.)Contact with metals may evolve flammable hydrogen gas. Containers may explode when heated or if contaminated with water. Substance may be transported in a molten form.
Combustion products
Fire will produce irritating, corrosive and/or toxic gases. Reaction with water may generate much heat which will increase the concentration of fumes in the air.
Health
3
 
Flammability
0
 
 
Reactivity
2
 

Health.
Poison_Class
2
Exposure effects
   Ingestion
May cause severe and permanent damage to the digestive tract. Causes gastrointestinal tract burns.
   Inhalation
May cause severe irritation of the respiratory tract with sore throat, coughing, shortness of breath and delayed lung edema. Causes chemical burns to the respiratory tract.
   Skin
Causes skin burns.
   Eyes
Causes eye burns.

First aid
 
   Ingestion
Do NOT induce vomiting. If victim is conscious and alert, give 2-4 cupfuls of milk or water. Never give anything by mouth to an unconscious person. Get medical aid immediately.
   Inhalation
Get medical aid immediately. Remove from exposure to fresh air immediately. If breathing is difficult, give oxygen. DO NOT use mouth-to-mouth respiration. If breathing has ceased apply artificial respiration using oxygen and a suitable mechanical device such as a bag and a mask.
   Skin
Get medical aid immediately. Flush skin with plenty of soap and water for at least 15 minutes while removing contaminated clothing and shoes. Wash clothing before reuse. Discard contaminated clothing in a manner which limits further exposure. Destroy contaminated shoes.
   Eyes
Immediately flush eyes with plenty of water for at least 15 minutes, occasionally lifting the upper and lower eyelids. Get medical aid immediately. Do NOT allow victim to rub or keep eyes closed. Extensive irrigation is required (at least 30 minutes).

Transport.
UN number
1829
Response guide
Hazard class
8
PRTC
T
Packing Group
I
 
USCG CHRIS Code
SLT
 
Std. Transport #
4930050 4936565