LABORATORY CHEMICAL SAFETY SUMMARY: METHYL IODIDE

Substance

Methyl iodide

(Iodomethane)

CAS 74-88-4

 

Formula

CH3I

 

Physical Properties

Colorless liquid; may darken upon exposure to light

bp 42 °C, mp -66 °C

Slightly soluble in water (2 g/100 mL)

 

Odor

Sweet, ethereal odor (no threshold data available); inadequate warning properties

Vapor Density

4.9 (air = 1.0)

 

Vapor Pressure

400 mmHg at 25 °C

 

Flash Point

Noncombustible

 

Toxicity Data

LDLO oral (rat)

150 mg/kg

 

LDLO skin (rat)

800 mg/kg

 

LC50 inhal (rat)

1300 mg/m3 (4 h)

 

PEL (OSHA)

5 ppm(28 mg/m3)—skin

 

TLV-TWA (ACGIH)

2 ppm(11 mg/m3)—skin

Major Hazards

Moderately toxic, volatile substance readily absorbed through skin.

Toxicity

The acute toxicity of methyl iodide is moderate by ingestion, inhalation, and skin contact. This substance is readily absorbed through the skin and may cause systemic toxicity as a result. Methyl iodide is moderately irritating upon contact with the skin and eyes. Methyl iodide is an acute neurotoxin. Symptoms of exposure (which may be delayed for several hours) can include nausea, vomiting, diarrhea, drowsiness, slurred speech, visual disturbances, and tremor. Massive overexposure may cause pulmonary edema, convulsions, coma, and death.

Chronic exposure to methyl iodide vapor may cause neurotoxic effects such as dizziness, drowsiness, and blurred vision. There is limited evidence for the carcinogenicity of methyl iodide to experimental animals; it is not classified as an OSHA "select carcinogen."

Flammability and Explosibility

Noncombustible. High vapor pressure may cause containers to burst at elevated temperatures.

Reactivity and Incompatibility

Methyl iodide may react vigorously with alkali metals and strong oxidizing agents.



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