NIOSH Pocket Guide to Chemical Hazards

Trimethyl phosphite

CAS 121-45-9


RTECS TH1400000
Synonyms & Trade Names
Methyl phosphite, Trimethoxyphosphine, Trimethyl ester of phosphorous acid
DOT ID & Guide
2329 129


NIOSH REL: TWA 2 ppm (10 mg/m3)
OSHA PEL: none
IDLH N.D. See: IDLH INDEX Conversion 1 ppm = 5.08 mg/m3
Physical Description
Colorless liquid with a distinctive, pungent odor.
MW: 124.1
BP: 232°F
FRZ: -108°F
Sol: Reacts
VP(77°F): 24 mmHg
IP: ?

Sp.Gr: 1.05
Fl.P: 82°F
UEL: ?
LEL: ?

Class IC Flammable Liquid: Fl.P. at or above 73F and below 100F.
Incompatibilities & Reactivities
Magnesium perchlorate, water [Note: Reacts (hydrolyzes) with water.]
Measurement Methods
None available
See: NMAM or OSHA Methods
Personal Protection & Sanitation (See protection)
Skin: Prevent skin contact
Eyes: Prevent eye contact
Wash skin: When contaminated
Remove: When wet (flammable)
Change: No recommendation
Provide: Quick drench
First Aid (See procedures)
Eye: Irrigate immediately
Skin: Soap flush immediately
Breathing: Respiratory support
Swallow: Medical attention immediately
Important additional information about respirator selection
Respirator Recommendations Not available.
Exposure Routes inhalation, ingestion, skin and/or eye contact
Symptoms Irritation eyes, skin, upper respiratory system; dermatitis; in animals: teratogenic effects
Target Organs Eyes, skin, respiratory system, reproductive system