HYDROGEN FLUORIDE AND HYDROFLUORIC ACID

Hydrogen fluoride and hydrofluoric acid
CAS 7664-39-3

HF

Colorless, clear, fuming liquid
Anhydrous HF: bp 20 °C, mp -83 °C
Miscible with water

Acrid, irritating odor

Anhydrous HF: 775 mmHg at 20 °C
Hydrofluoric acid: 14 mmHg at 20 °C

Noncombustible

LC_LO inhal (humans) 50 ppm (0.5 h)

PEL (OSHA) 3 ppm (as fluoride)

TLV-TWA (ACGIH) 3 ppm (2.6 mg/m³; ceiling as fluoride)

Extremely corrosive liquid and vapor that can cause severe injury via skin and eye contact, inhalation, or ingestion.

Anhydrous hydrogen fluoride and hydrofluoric acid are extremely corrosive to all tissues of the body. Skin contact results in painful deep-seated burns that are slow to heal. Burns from dilute (<50%) HF solutions do not usually become apparent until several hours after exposure; more concentrated solutions and anhydrous HF cause immediate painful burns and tissue destruction. HF burns pose unique dangers distinct from other acids such as HCl and H₂ SO₄: undissociated HF readily penetrates the skin, damaging underlying tissue; fluoride ion can then cause destruction of soft tissues and decalcification of the bones. Hydrofluoric acid and HF vapor can cause severe burns to the eyes, which may lead to permanent damage and blindness. At 10 to 15 ppm, HF vapor is irritating to the eyes, skin, and respiratory tract. Exposure to higher concentrations can result in serious damage to the lungs, and fatal pulmonary edema may develop after a delay of several hours. Brief exposure (5 min) to 50 to 250 ppm may be fatal to humans. Ingestion of HF can produce severe injury to the mouth, throat, and gastrointestinal tract and may be fatal.

HF has not been reported to be a human carcinogen. No acceptable animal test reports are available to define the developmental or reproductive toxicity of this substance.

Hydrogen fluoride is not a combustible substance.

HF reacts with glass, ceramics, and some metals. Reactions with metals may generate potentially explosive hydrogen gas.

Dilute solutions of hydrofluoric acid (<50%) should be handled using the "basic prudent practices" of Chapter 5.C. Because of its corrosivity and high acute toxicity, anhydrous hydrogen fluoride and concentrated solutions of HF should be handled using the "basic prudent practices" of Chapter 5.C, supplemented by the additional precautions for work with compounds of high toxicity (Chapter 5.D). All work with HF should be conducted in a fume hood to prevent exposure by inhalation, and splash goggles and neoprene gloves should be worn at all times to prevent eye and skin contact. Containers of HF should be stored in secondary containers made of polyethylene in areas separate from incompatible materials. Work with anhydrous HF should be undertaken using special equipment and only by well-trained personnel familiar with first aid procedures.

Laboratory personnel should be familiar with first aid procedures before beginning work with HF; calcium gluconate gel should be readily accessible in areas where HF exposure potential exists.

First aid must be started within seconds in the event of contact of any form. In the event of skin contact, immediately wash with water for 15 min and remove contaminated clothing. If available, apply calcium gluconate gel. Obtain medical attention at once, and inform attending physician that injury involves HF rather than other acid. In case of eye contact, promptly wash with copious amounts of water for 5 min while holding the eyelids apart and seek medical attention at once. If HF is ingested, obtain medical attention immediately. If HF vapor is inhaled, move the person to fresh air and seek medical attention at once.

In the event of a spill of dilute hydrofluoric acid, soak up the acid with an HF-compatible spill pillow or neutralize with lime, transfer material to a polyethylene container, and dispose of properly. Respiratory protection may be necessary in the event of a large spill or release in a confined area. Releases of anhydrous HF require specially trained personnel.

Excess hydrogen fluoride 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.