Boron trifluoride

(Boron fluoride, trifluoroborane)

CAS 7637-07-2





Physical Properties

Colorless gas, fumes in moist air

bp -100 °C, mp -127 °C

Highly soluble in cold water (332 g/100 mL)



Pungent odor detectable at 1.5 ppm

Vapor Density

2.4 (air = 1.0)


Vapor Pressure

>1 mmHg at 20 °C


Flash Point



Toxicity Data

LC50 inhal (rat)

387 ppm (1070 mg/m3; 1 h)



1 ppm (3 mg/m3; ceiling)



1 ppm (3 mg/m3; ceiling)

Major Hazards

Highly corrosive to skin, eyes, and mucous membranes; reacts violently with water to form highly toxic HF.


Boron trifluoride (and organic complexes such as BF3-etherate) are extremely corrosive substances that are destructive to all tissues of the body. Upon contact with moisture in the skin and other tissues, these compounds react to form hydrofluoric acid and fluoroboric acid, which cause severe burns. Boron trifluoride gas is extremely irritating to the skin, eyes, and mucous membranes. Inhalation of boron trifluoride can cause severe irritation and burning of the respiratory tract, difficulty breathing, and possibly respiratory failure and death. Exposure of the eyes to BF3 can cause severe burns and blindness. This compound is not considered to have adequate warning properties.

Boron trifluoride has not been found to be carcinogenic or to show reproductive or developmental toxicity in humans. Chronic exposure to boron trifluoride gas can cause respiratory irritation and damage.

Flammability and Explosibility

Boron trifluoride gas is noncombustible. Water should not be used to extinguish any fire in which boron trifluoride is present. Dry chemical powder should be used for fires involving organic complexes of boron trifluoride.

Reactivity and Incompatibility

Boron trifluoride reacts violently with water and alkali and alkaline earth metals such as sodium, potassium, and calcium. It may react exothermically with alkyl nitrates, ethylene oxide, and butadiene.

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