LABORATORY CHEMICAL SAFETY SUMMARY: METHYL ETHYL KETONE

Substance

Methyl ethyl ketone

(2-Butanone, methyl acetone, MEK, butan-2-one)

CAS 78-93-3

 

Formula

CH3COCH2CH3

 

Physical Properties

Colorless liquid

bp 80 °C, mp -86 °C

Highly soluble in water (25.6 g/100 mL at 20 °C)

 

Odor

Sweet/sharp odor detectable at 2 to 85 ppm (mean = 16 ppm)

Vapor Density

2.5 (air = 1.0)

 

Vapor Pressure

71.2 mmHg at 20 °C

 

Flash Point

-9 °C

 

Autoignition Temperature

516 °C

 

Toxicity Data

LD50 oral (rat)

2737 mg/kg

 

LD50 skin (rabbit)

6480 mg/kg

 

LC50 inhal (rat)

23,500 mg/m3 (8 h)

 

PEL (OSHA)

200 ppm (590 mg/m3)

 

TLV-TWA (ACGIH)

200 ppm (590 mg/m3)

 

STEL (ACGIH)

300 ppm(885 mg/m3)

Major Hazards

Highly flammable

Toxicity

The acute toxicity of methyl ethyl ketone is low. Exposure to high concentrations can cause headache, dizziness, drowsiness, vomiting, and numbness of the extremities. Irritation of the eyes, nose, and throat can also occur. Methyl ethyl ketone is considered to have adequate warning properties.

Repeated or prolonged skin exposure to methyl ethyl ketone can cause defatting of the skin, leading to cracking, secondary infection, and dermatitis. This compound has not been found to be carcinogenic or to show reproductive or developmental toxicity in humans. Methyl ethyl ketone has exhibited developmental toxicity in some animal tests.

Flammability and Explosibility

Methyl ethyl ketone is extremely flammable (NFPA rating = 3), and its vapor can travel a considerable distance to an ignition source and "flash back." MEK vapor forms explosive mixtures with air at concentrations of 1.9 to 11% (by volume). Carbon dioxide or dry chemical extinguishers should be used for MEK fires.



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