# NIOSH Pocket Guide to Chemical Hazards
Sodium metabisulfite | CAS 7681-57-4
Na2S2O5 | RTECS UX8225000
Synonyms & Trade Names Disodium pyrosulfite, Sodium metabisulphite, Sodium pyrosulfite | DOT ID & Guide
Exposure Limits | NIOSH REL: TWA 5 mg/m3
OSHA PEL†: none
IDLH N.D. | Conversion
Physical Description White to yellowish crystals or powder with an odor of sulfur dioxide.
MW: 190.1 | BP: Decomposes | MLT: >302°F (Decomposes) | Sol: 54%
VP: ? | IP: NA |  | Sp.Gr: 1.4
Fl.P: NA | UEL: NA | LEL: NA |
Noncombustible Solid
Incompatibilities & Reactivities Heat (decomposes) [Note: Slowly oxidized to the sulfate on exposure to air & moisture.]
Measurement Methods NIOSH 0500
Personal Protection & Sanitation Skin: No recommendation Eyes: No recommendation Wash skin: No recommendation Remove: No recommendation Change: No recommendation | First Aid (See procedures) Eye: Irrigate immediately Breathing: Fresh air Swallow: Medical attention immediately
Respirator Recommendations To be added later
Exposure Routes inhalation, ingestion, skin and/or eye contact
Symptoms Irritation eyes, skin, mucous membrane
Target Organs Eyes, skin, respiratory system
See also: INTRODUCTION