METHYL IODIDE

Methyl iodide
(Iodomethane)
CAS 74-88-4

CH₃I

Colorless liquid; may darken upon exposure to light
bp 42 °C, mp -66 °C
Slightly soluble in water (2 g/100 mL)

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

4.9 (air = 1.0)

400 mmHg at 25 °C

Noncombustible

LD_LOO oral (rat) 150 mg/kg

LD_LOO 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

Moderately toxic, volatile substance readily absorbed through skin.

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."

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

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

Methyl iodide should be handled using the "basic prudent practices" of Chapter 5.C.

In the event of skin contact, immediately wash with soap and water and remove contaminated clothing. In case of eye contact, promptly wash with copious amounts of water for 15 min (lifting upper and lower lids occasionally) and obtain medical attention. If methyl iodide is ingested, obtain medical attention immediately. If large amounts of this compound are inhaled, move the person to fresh air and seek medical attention at once.

In the event of a spill, soak up methyl iodide with a spill pillow or absorbent material, place in an appropriate container, and dispose of properly. Respiratory protection may be necessary in the event of a large spill or release in a confined area.

Excess methyl iodide and waste material containing this substance should be placed in an appropriate container, clearly labeled, and handled according to your institution's waste disposal guidelines.

The information in this LCSS has been compiled by a committee of the National Research Council from literature sources and Material Safety Data Sheets and is believed to be accurate as of July 1994. This summary is intended for use by trained laboratory personnel in conjunction with the NRC report Prudent Practices in the Laboratory: Handling and Disposal of Chemicals. This LCSS presents a concise summary of safety information that should be adequate for most laboratory uses of the title substance, but in some cases it may be advisable to consult more comprehensive references. This information should not be used as a guide to the nonlaboratory use of this chemical.

Copyright 1995 National Academy of Sciences. All rights reserved.