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DESIGNATIONS
CAS No.: 7664-39-3
Registry name: Hydrogen fluoride
Chemical name: Hydrogen fluoride
Synonyms, Trade names: Hydrogen fluoride (anhydrous), anhydrous hydrofluoric acid, AHF
as aqueous solutions: hydrofluoric acid, acidum hydrofluorium
Chemical name (German): Fluorwasserstoff (wasserfrei), Flußsäure (wasserfrei)
Chemical names (French): Fluorure d'hydrogène (anhydre), acide hydrofluorique (anhydre)
Appearance: colourless, highly mobile, caustic liquid with penetrating odour
BASIC CHEMICAL AND PHYSICAL DATA
| Empirical formula: | HF (mostly as (HF)6 to (HF)x) |
| Rel. molecular mass: | 20.01 g |
| Density: | 1.015 g/cm3 at 0°C, 0.901 g/cm3 at boiling point |
| Relative gas density: | 1.77 |
| Boiling point: | 19.51°C |
| Melting point: | -83.55°C |
| Vapour pressure: | 105 Pa at 20°C, 1.5 x 105 Pa at 30°C, 2.8 x 105 Pa at 50°C |
| Odour threshold: | 0.03 mg/m3 |
| Solvolysis/solubility: | - HF is extremely hygroscopic and miscible in any ratio with water and numerous organic substances (e.g. with alcohols, ethers, ketones and nitriles). |
| - Scarcely miscible with hydrocarbons and their halogen derivates | |
| Conversion factors: | 1 ppm = 0.832 mg/m3 |
| 1 mg/m3 = 1.20 ppm |
ORIGIN AND USE
Usage:
Anhydrous hydrogen fluoride is used mainly to produce aerosol
fluorocarbons (propellants, refrigerators) as well as metal
fluorides, ammonia hydrogen fluoride and fluorosulphuric acid. It
is likewise used to desulphurise gas oils and as a solvent in
chemical laboratories.
Origin/derivation:
HF issues from rock magma and is thus encountered above all in
volcanically active areas (e.g. approx. 200,000 t/a in the
'Valley of the 10,000 Vapours' covering 72 km2 in
Alaska).
The industrial production of HF involves the heating of fluorides with concentrated sulphuric acid or thermal decomposition of fluorosilicic acid with the formation of silicon tetrafluoride.
Production figures:
In the "Western" world: 1964 approx.
555,000 t; 1970 approx. 960,000 t; 1972 approx.
1,045,000 t; 1980 approx. 1,820,000 t (ULLMANN, 1985),
1982 approx. 860,000 t (ULLMANN, 1988)
Emissions:
In addition to natural sources, emissions are to be expected from
all industries using HF such as aluminium foundries and
glassworks, brickworks, enamelling companies and phosphate
factories.
Toxicity
| Humans: | LD50 ppm, inhalation (30-60 min) | acc. HOMMEL, 1987 |
| Mammals: | ||
| Rat | LD50 1276 ppm, inhalation (1 h) | acc. ROTH, 1988 |
| Aquatic organisms: | ||
| Fish | LC 60 mg/l | acc. HOMMEL, 1987 |
| Fish | LC0 0.63 µg/l | acc. HOMMEL, 1987 |
| Bacteria | 0.63 µg/l (inhibited cell reproduction) | acc. HOMMEL, 1987 |
| Plants: | ||
| Crocus | 2 µg/m3 (276 h, extremely severe leaf necroses) | acc. VDI, 1987 |
| Spruce | 5.4 µg/m3 (270 h, severe necroses) | acc. VDI, 1987 |
| Maize | 4.7 µg/m3 (7 d, 7% leaf chloroses) | acc. VDI, 1987 |
| Narcissus | 2 µg/m3 (276 h, slight to moderate leaf necroses) | acc. VDI, 1987 |
| Chrysanthemum | 25 µg/m3 (114 h, very slight chloroses) | acc. VDI, 1987 |
Classification of plant species according to their relative fluoride sensitivity (from VDI, 1987):
Highly sensitive
| American larch | Douglas fir | Mahonia | St. John's wort |
| Apricot | Fan maple | Mountain ash | Spruce |
| Ash maple | Gladiolus | Mountain pine | Tulip |
| Bilberry | Lilac | Onion | Vine |
| Common pine | Hornbeam | Peach | Weymouth pine |
| Coral tree | Iris | Plum | Yellow pine |
| Cranberry | Japanese larch | Silver fir | |
| Crocus family | Lily-of-the-valley | Sorghum |
Sensitive
| Acer platanoides | Common pine | Lucerne | Spinach |
| Alpine knotgrass | Copperbeech | Maize family | Spruce |
| Amaranth | Cranesbill family | Mangel wurzel | Stellaria media |
| Ambrosia | Cultivated strawberries | Melilotus | Sumach |
| Apple | Cultivated carnation | Mountain ash | Sunflower |
| Apricot | Dahlia family | Narcissus family | Sweet cherry |
| Arborvitae family | Dock | Prunis padus | Sweet potato |
| Aspen poplar | Douglas fir | Peony family | Tea-rose |
| Aster family | Dwarf mountain pine | Peach | Tomato |
| Beech family | European larch | Rye | Vines |
| Begonia family | Field maple | Raspberry | Violet |
| Black pine | Giant sequoia | Red mulberry | Walnut |
| Black poplar | Golden rod family | Rhododendron family | Wild sorghum |
| Black walnut | Green ash | Rhubarb | Willow family |
| Canadian amelanchier | Hybrid poplar | Seed oats | Winter linden |
| Chenopodium album | Incarnate clover | Seed wheat | |
| Cherry plum | Japanese yew | Silver maple | |
| Colorado fir | Lilac | Sorghum |
Less sensitive
| Ailanthus glandulosa | Canadian amelanchier | Dwarf medlar | Prunis padus |
| Amaranth | Carrot | Elaeagnus | Raspberry |
| American linden | Celery | False cypress | Robinia |
| American plane | Cherry plum | Forsythia | Siberian elm |
| Arborvitae | Chinese elm | Flowering cherry | Snowberry |
| Aubergine | Chinese juniper | Hemlock spruce | Soja bean |
| Asparagus family | Chrysanthemum family | Lucerne | Sugar cane |
| Berberis | Coffee tree | Mountain ash | Sumach |
| Balsam poplar | Columbine family | Oak family | Tobacco |
| Black alder | Cornaceae | Pea | Tomato |
| Black elder | Cotton | Pear | Wheat family |
| Black nightshade | Cucumber | Petunia | White beech |
| Blackcurrent | Cultivated antirrhinum | Philadelphus coronarius | Wild vine |
| Buckthorn | Cultivated bean | Plane | Willow family |
| Burdock family | Cultivated pumpkin | Plantain family | Yarrow |
| Cabbage | Cultivated strawberry | Potato | Yew |
| Camellia | Dock family | Privet family |
Characteristic effects:
Humans/mammals: HF is caustic and can severely damage the respiratory tract with pulmonary oedemas. Symptoms of acute poisoning are burning of the eyes, the skin, the nasal mucous membranes and the mucous membranes in the throat. Long-term inhalation of HF can cause fluorosis (= osteosclerosis) even at small concentrations. Grazing cattle have been found to produce less milk, to grow less, to suffer paralysis and to have damaged teeth following poisoning. Fluorosis is also possible with cattle. Damage to health can occur as soon as the odour becomes perceptible. Fluorine is found as a trace element in bones and teeth. A lack of fluorine may damage human teeth (e.g. caries).
Plants: HF is the most phytotoxic gas. However, the compatibility of plants to HF varies significantly among the various species depending e.g. on the age of the leaves and the stage of development. HF influences the enzyme activity and causes necroses. Damage due to HF is similar to arid damage.
ENVIRONMENTAL BEHAVIOUR
Water:
HF dissolves completely in water with considerable amounts of
heat being liberated. Corrosive and toxic mixtures may form over
the surface of water. Extremely acidic with little dissociation
in aqueous solutions.
Air:
HF develops smoky clouds in humic air. Corrosive mists are formed
and remain at ground level because of the relative gas density.
Soil:
Depending on the type of soil, fluorine is found in the form of
fluorides as a natural element in concentrations between 10 and
150 ppm. HF causes only little acidification of the soil as
it is readily bonded through the effect of lime. Damage to plants
as a result of uptake from the soil is only a minor problem.
Conversion, degradation, decomposition products, half-life:
Fluorides may be produced. Most metal fluorides are soluble in
water; PbF2, CuF2 and certain
alkaline-earth fluorides are hardly soluble in water or not at
all.
ENVIRONMENTAL STANDARDS
| Medium/ acceptor | Sector | Country/ organ. | Status |
Value | Cat. | Remarks | Source |
| Water: | Emiss. | D | L |
5 mg/m3 | mass flow > 50 g/h12) | acc. TA Luft, 1986 | |
| D | G |
1 | WGK | acc. HOMMEL, 1987 | |||
| Air: | D | L |
1 µg/m3 | IW1 | 11) | acc. TA Luft, 1986 | |
| D | L |
3 µg/m3 | IW2 | 11) | acc. TA Luft, 1986 | ||
| CDN | (L) |
1.5 µg/m3 | 24 h, Manitoba | acc. UBA, 1981 | |||
| CDN | (L) |
4.5 µg/m3 | 24 h, Newfoundland | acc. UBA, 1981 | |||
| CDN | (L) |
26 µg/m3 | 24 h, Ontario1) | acc. UBA, 1981 | |||
| CDN | (L) |
7 µg/m3 | 24 h, Ontario2) | acc. UBA, 1981 | |||
| CDN | (L) |
3 µg/m3 | 24 h, Saskatch. | acc. UBA, 1981 | |||
| DDR | (L) |
5 µg/m3 | 24 h | acc. DORNIER, 1984 | |||
| DDR | (L) |
20 µg/m3 | 30 min | acc. DORNIER, 1984 | |||
| E | (L) |
10 µg/m3 | 24 h | acc. DORNIER, 1984 | |||
| E | (L) |
30 µg/m3 | 30 min | acc. DORNIER, 1984 | |||
| H | (L) |
20 µg/m3 | 24 h3) | acc. DORNIER, 1984 | |||
| H | (L) |
1.3 µg/m3 | 24 h4) | acc. DORNIER, 1984 | |||
| H | (L) |
5 µg/m3 | 30 min4) | acc. DORNIER, 1984 | |||
| NL | (L) |
10 µg/m3 | 24 h | acc. DORNIER, 1984 | |||
| RO | (L) |
5 µg/m3 | 24 h | acc. DORNIER, 1984 | |||
| RO | (L) |
20 µg/m3 | 30 min | acc. DORNIER, 1984 | |||
| SU | (L) |
10 µg/m3 | 24 h5) | acc. DORNIER, 1984 | |||
| SU | (L) |
30 µg/m3 | 30 min5) | acc. DORNIER, 1984 | |||
| YU | (L) |
5 µg/m3 | 24 h | acc. DORNIER, 1984 | |||
| YU | (L) |
20 µg/m3 | 30 min | acc. DORNIER, 1984 | |||
| Workp | D | L |
2 mg/m3 | MAK | 8 h mean | DFG, 1989 | |
| Workp | D | L |
3 ml/m3 | MAK | 8 h mean | DFG, 1989 | |
| Workp | USA | (L) |
2.5 mg/m3 | TLV-C | Ceiling value | ACGIH, 1986 | |
| Workp | USA | (L) |
2 ppm | TLV-C | Ceiling value | ACGIH, 1986 | |
| Workp | D | L |
4 mg/g (aqu) | BAT | Urine11) | DFG, 1988 | |
| D | G |
1 µg/m3 | 1 d, plants6) | VDI, 1987 | |||
| D | G |
0.25 µg/m3 | 1 mon, plants6) | VDI, 1987 | |||
| D | G |
0.15 µg/m3 | 7 mon, plants6) | VDI, 1987 | |||
| D | G |
2 µg/m3 | 1 d, plants7) | VDI, 1987 | |||
| D | G |
0.6 µg/m3 | 1 mon, plants7) | VDI, 1987 | |||
| D | G |
0.4 µg/m3 | 7 mon, plants7) | VDI, 1987 | |||
| D | G |
6 µg/m3 | 1 d, plants8) | VDI, 1987 | |||
| D | G |
1.8 µg/m3 | 1 mon, plants8) | VDI, 1987 | |||
| D | G |
1.2 µg/m3 | 7 mon, plants8) | VDI, 1987 | |||
| USA | G |
2.7 µg/m3 | 1 d, pesticide | acc. ULLMANN, 1985 | |||
| USA | G |
0.78 µg/m3 | 1 mon, pesticide | acc. ULLMANN, 1985 | |||
| USA | G |
0.5 µg/m3 | Vegetat. period | acc. ULLMANN, 1985 | |||
| Foodstuffs: | |||||||
| Working animals | Fodder | D | L |
30 mg/kg (88% DS) | 9) | acc. BAFEF, 1987 | |
| Fodder | D | L |
50 mg/kg | 10) | acc. BAFEF, 1987 | ||
| Fodder | D | L |
100 mg/kg | Pigs | acc. BAFEF, 1987 | ||
| Fodder | D | L |
350 mg/kg | Poultry | acc. BAFEF, 1987 | ||
| Fodder | D | L |
150 mg/kg | Other animals | acc. BAFEF, 1987 | ||
Notes:
1) For industrial and business conurbations
2) For residential and rural areas
3) For protected areas
4) For specially protected areas
5) For residential areas
6) Highly sensitive plants
7) Sensitive plants
8) Less sensitive plants
9) Lactating cattle, sheep, goats
10) Other cattle, sheep, goats
11) HF and ist inorganic gaseous compounds, stated as F
12) F and ist vapourous/gaseous compounds, stated as HF
Assessment/comments
When released into the atmosphere, hydrogen fluoride can prove
to be a potent plant killer. Therefore, it should only be
released in small quantities. Numerous limit values for differing
exposure periods were established by the VDI in 1987.
The addition of fluoride to drinking water is the subject of
debate. It has been proven beyond doubt that a lack of fluorine
is harmful to the teeth, but the absorption of major quantities
of fluorine is harmful to both humans and animals.
The information available to date does not permit conclusive
assessment.