Reactivity Profile
HYDROGEN FLUORIDE, ANHYDROUS attacks glass and any other silica containing material. May react with common metals (iron, steel) to generate flammable hydrogen gas if diluted below 65% with water. Reacts exothermically with chemical bases (examples: amines, amides, inorganic hydroxides). Can initiate polymerization in certain alkenes. Reacts with cyanide salts and compounds to release gaseous hydrogen cyanide. May generate flammable and/or toxic gases with dithiocarbamates, isocyanates, mercaptans, nitrides, nitriles, sulfides. Additional gas-generating reactions may occur with sulfites, nitrites, thiosulfates (to give H2S and SO3), dithionites (SO2), and carbonates. Can catalyze (increase the rate of) chemical reactions. Reacts explosively with cyanogen fluoride, methanesulfonic acid or glycerol mixed with nitric acid. Reacts violently with arsenic trioxide, phosphorus pentachloride, acetic anhydride, alkali metals, ammonium hydroxide, chlorosulfonic acid, ethylenediamine, fluorine, potassium permanganate, oleum, propylene oxide, vinyl acetate, mercury(II) oxide. Emits highly corrosive fumes of hydrogen fluoride gas when heated [Sax, 9th ed., 1996, p. 1839]. Contact with many silicon compounds and metal silicides causes violent evolution of gaseous silicon tetrafluoride [Mellor, 1956, Vol. 2, suppl. 1, p. 121].
Air & Water Reactions
Fumes in air. Fumes are highly irritating, corrosive, and poisonous. Generates much heat on dissolution [Merck, 11th ed., 1989]. Heat can cause spattering, fuming, etc.
Hazard
Toxic by ingestion and inhalation, highly
corrosive to skin and mucous membranes.
Health Hazard
Ingestion of an estimated 1.5 grams produced sudden death without gross pathological damage. Repeated ingestion of small amounts resulted in moderately advanced hardening of the bones. Contact of skin with anhydrous liquid produces severe burns. Inhalation of anhydrous hydrogen fluoride or hydrogen fluoride mist or vapors can cause severe respiratory tract irritation that may be fatal.
Fire Hazard
When heated, HYDROGEN FLUORIDE, ANHYDROUS emits highly corrosive fumes of fluorides. Its corrosive action on metals can result in formation of hydrogen in containers and piping to create fire hazard. Toxic and irritating vapors are generated when heated. Will attack glass, concrete, and certain metals, especially those containing silica, such as cast iron. Will attack natural rubber, leather, and many organic materials. May generate flammable hydrogen gas in contact with some metals.
History
Anhydrous hydrogen fluoride was first prepared by Fremy in 1856. It mayhave been made earlier in 1670 by Schwankhard in the process of etchingglass using fluorspar and acid.
Hydrogen fluoride is the most important fluorine compound, in terms ofamounts produced and the vast number of uses. The largest application of thiscompound is in the manufacture of aluminum fluoride and sodium aluminumfluoride (cryolite) for electrolytic production of aluminum. Another majorapplication is in the manufacture of chlorofluorocarbons, which are used asrefrigerants and foaming agents; for making polymers; and for pressurizinggases. Another important application is in the processing of uranium whereHF converts uranium dioxide to uranium tetrafluoride and hexafluoride,respectively. Uranium hexafluoride is used to separate isotopes of uraniumby diffusion.
Hydrogen fluoride also is used as a catalyst in alkylation of aromatic com-pounds and for dimerization of isobutene. Other catalytic applications are inisomerization, polymerization, and dehydration reactions. Other uses are in366HYDROGEN FLUORIDEpp-03-25-new dots.qxd 10/23/02 2:38 PM Page 366 etching and polishing glasses for manufacturing light bulbs and TV tubes; inextraction of ores; in pickling stainless steel; in acidizing oil-wells; to removelaundry stains; for sample digestion in metal analysis; for removal of sandduring metal castings; as a stabilizer for rocket propellant oxidizers; and inpreparation of a number of fluoride alts of metals.
Definition
A colorless liquid produced
by dissolving hydrogen fluoride in water. It
is a weak acid, but will dissolve most silicates
and hence can be used to etch glass.
As the interatomic distance in HF is relatively
small, the H–F bond energy is very
high and hydrogen fluoride is not a good
proton donor. It does, however, form hydrogen
bonds.
Definition
ChEBI: A diatomic molecule containing covalently bonded hydrogen and fluorine atoms.
Production Methods
Anhydrous hydrogen fluoride is manufactured by the action of sulfuric on calcium fluoride. Powdered acid-grade fluorspar (≥97% CaF2) is distilled with concentrated sulfuric acid; the gaseous hydrogen fluoride that leaves the reactor is condensed and purified by distillation.
Anhydrous hydrogen fluoride is manufactured by treating fluorspar (fluorite, CaF2) with concentrated sulfuric acid in heated kilns. The gaseous HF evolved is purified by distillation, condensed as liquid anhydrous HF, and stored in steel tanks and cylinders.
General Description
HF is a colorless inorganic acid. Hydrogen fluoride may be formed by reacting calcium fluoride and sulfuric acid at 200oC. The fluoride in the acid has very high affinity to silicon, making it useful in etching or removal of silicon.
Flammability and Explosibility
Hydrogen fluoride is not a combustible substance
Industrial uses
Hydrofluoric acid (HF) is a colorless liquid with a characteristic odor. It releases fumes
when in contact with moist air. Hydrofluoric acid is manufactured from fluorite containing
96–97% CaF2 by reacting it with concentrated sulfuric acid:
CaF2+H2SO4 = 2HF+CaSO4
The acid is sold as a 40% solution. The hydrofluoric acid is used as an activator and
depressant, mostly during flotation of industrial minerals (i.e. columbite, tantalite,
silica, feldspars).
Materials Uses
Carbon steel (without nonmetallic inclusions) is
acceptable for handling hydrogen fluoride up to
approximately 150°F (65.6°C). Aluminum-
silicon-bronze, stainless steel, or nickel are
suitable for cylinder valves. For higher temperatures,
Monel, Inconel, nickel, or copper
should be used. Cast iron or malleable fittings
should be avoided. Polyethylene, lead, soft copper,
Kel-F, and Teflon are acceptable gasket
materials. Polyethylene, Kel-F, and Teflon are
acceptable packing materials.
Potential Exposure
Mutagen;Reproductive Efector; Human Data; Primary Irritant.Hydrogen fluoride, its aqueous solution hydrofluoric acid,and its salts, are used in special metallurgical process;nuclear engineering; making organic and inorganic fluorinecompounds, such as fluorides and plastics; as a catalyst,particularly in paraffin alkylation in the petroleum industry;as an insecticide; and to arrest the fermentation in brewing.It is utilized in the fluorination processes, especially in thealuminum industry; in separating uranium isotopes; incleaning cast iron, copper, and brass; in removing efflores-cence from brick and stone; in removing sand from metalliccastings; in frosting and etching glass and enamel; in pol-ishing crystal; in decomposing cellulose; in enameling andgalvanizing iron; in working silk; in dye and analyticalchemistry; and to increase the porosity of ceramics.
Physiological effects
Hydrogen fluoride is highly corrosive to all
living tissue. Contact with liquid anhydrous
hydrogen fluoride, its vapor, or hydrogen fluoride
solutions can cause severe bums to skin,
eyes, or respiratory tract. ACGIH recommends a
Threshold Limit Value-Ceiling (TLV-C) of 3
ppm (2.3 mg/m3
) fi)r hydrogen fluoride (as F).
The TLV-C is the concentration that should not
be exceeded during any part of the working
exposure .
First aid
If this chemical gets into the eyes, remove anycontact lenses at once (contact lenses should not be wornwhen working with HF) and irrigate immediately for atleast 30 min, occasionally lifting upper and lower lids. Seekmedical attention immediately. If this chemical contacts theskin, remove contaminated clothing and flush immediatelywith large amounts of water. Immerse exposed skin area iniced 70% ethyl alcohol. Seek medical attention immedi-ately. If this chemical has been inhaled, remove from expo-sure, begin rescue breathing (using universal precautions,including resuscitation mask) if breathing has stopped andCPR if heart action has stopped. Transfer promptly to amedical facility. When this chemical has been swallowed,get medical attention. If victim is conscious， administerwater or milk. Do not induce vomiting. Medical observationis recommended for 24- 48 h after breathing overexposure,as pulmonary edema may be delayed. As first aid for pul-monary edema, a doctor or authorized paramedic may con-sider administering a corticosteroid spray.
Carcinogenicity
NTP conducted two chronic
oral bioassays of fluoride administered as sodium fluoride
(0, 25, 100, or 175 ppm) in drinking water for 103 weeks in
rats and mice.The first study was compromised, so it was
used to determine doses for the second study. NTP concluded
that there was no evidence that fluoride was carcinogenic at
doses up to 4.73 mg/kg/day in female rats or at doses up to
17.8 and 19.9 mg/kg/day in male and female mice,
respectively.
Environmental Fate
Hydrogen fluoride is a colorless, fuming liquid with a strong,
irritating odor. The density is 1.002 at 0 ℃ and the boiling
point is 19.51 ℃. Hydrogen Fluoride is naturally released into
the environment, primarily from volcanoes, ranging from 0.6
to 6 million metric tons per year. The majority of artificial
pollutants come from electrical utilities.
Hydrogen fluoride is removed from air by wet deposition as
fluoride salts with an atmospheric lifetime of 1–5 days.
storage
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.
Shipping
Hydrogen fluoride, anhydrous, requires a ship-pinglabel of “CORROSIVE， POISONOUS/TOXICMATERIALS.”It falls in Hazard Class 8 and PackingGroup I.Hydrofluoric acid, with >60% strength, requires a shippinglabelof“CORROSIVE,POISONOUS/TOXICMATERIALS." It falls in Hazard Class 8 and PackingGroup I.Hydrofluoric acid, with not >60% strength, requires a ship-ping .labelof“CORROSIVE,POISONOUS/TOXICMATERIALS." It falls in Hazard Class 8 and PackingGroup II.
Purification Methods
It can be purified by trap-to-trap distillation, followed by drying over CoF2 at room temperature and further distillation. Alternatively, it can be absorbed on NaF to form NaHF2 which is then heated under vacuum at 150o to remove volatile impurities. The HF is regenerated by heating at 300o and is stored with CoF3 in a nickel vessel, being distilled as required. (Water content should be ca 0.01%.) To avoid contact with base metal, use can be made of nickel, polychlorotrifluoroethylene and gold-lined fittings [Hyman et al. J Am Chem Soc 79 3668 1957]. An aqueous solution is hydrofluoric acid (see above). It is HIGHLY TOXIC and attacks glass.
Toxicity evaluation
HFA is toxic by ingestion, inhalation, and (most commonly) by
dermal exposure. It is highly corrosive to the skin and mucous
membranes with very short (5 s or less) exposure concentrations
of 0.003% and above, acting by protonation of tissues. It
causes a liquefying necrosis at the site of contact. Absorption of
fluoride ions leads to systemic fluoride poisoning, in turn
leading to hypokalemia and hypomagnesemia potentially
resulting in neuromuscular paralysis and cardiac arrhythmias.
Incompatibilities
HF reacts with glass, ceramics, and some metals. Reactions with metals may
generate potentially explosive hydrogen gas.
Waste Disposal
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. For more information on disposal procedures,
see Chapter 7 of this volume.
GRADES AVAILABLE
Anhydrous hydrogen fluoride is available from
a number of suppliers with grades ranging from
99.0 percent to 99.96 percent. The major impurities
are water (H20) and sulfur dioxide (S02).
