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Bromine

DESIGNATIONS

CAS No.: 7726-95-6
Registry name: Bromine
Chemical name : Bromine
Synonyms, Trade names: Bromine
Chemical name (German): Brom
Chemical name (French): Brome
Appearance: dark, reddish-brown, fuming, highly volatile liquid or vapour (below -7.2C metal-like crystals, colourless at -252C)

BASIC CHEMICAL AND PHYSICAL DATA

Empirical formula: Br2
Rel. molecular mass: 159.80 g
Density: 3.12 g/cm3
Relative gas density: 5.5
Boiling point: 58.78C
Melting point: -7.2C
Vapour pressure: 220 hPa at 20C; 340 hPa at 30C; 740 hPa at 50 C
Odour threshold: 1 ppm in air
Solvolysis/solubility: in water 42 g/l at 0C
35.5 g/l at 20C
soluble in benzene, gasoline, chloroform, ethanol, ether and hydrogen sulphide
Conversion factors: 1 mg/m3 = 0.150 ml/m3
1 ml/m3 = 6.658 mg/m3
Note: Apart from mercury, bromine is the only element which is liquid at room temperature. Bromine is highly reactive: it reacts explosively with several metals, corrodes many organic substances and reacts as an oxidising agent.

ORIGIN AND USE

Usage:
Most bromine (about 30 %) is used to produce 1,2-dibromoethane which is added to fuels containing tetraethyl lead to stop lead deposits collecting on the valves of internal-combustion engines. Further uses are the production of oil well packs and completion fluids as calcium bromide (22 %) and in flame retardants (16 %). It is used as starting material for the organic synthesis of pesticides, dyes, medicines, photographic chemicals and contrast media.

Origin/derivation:
Bromine is mainly obtained from waste lyes in the potassium industry; seawater is a further source. Waste lyes, brine and mother liquids etc. with a bromine content of > 1 g/l are processed by means of hot debromination, with cold debromination being used for seawater. Subsequent distillation and drying remove chlorine, residual water and impurities from the raw bromine segregated from the aqueous phase (99% yield).

Production figures:
Worldwide
1982 = 381,000 t (ULLMANN, 1985)
1983 = 364,200 t
1984 = 373,000 t

Toxicity

Humans: LDLo 14 mg/kg, oral acc. UBA, 1986
LCLo 1000 ppm, res. air (inhal.) = lethal acc. UBA, 1986
Mammals:
Mouse LC50 750 ppm (9 min), inhalation acc. UBA, 1986
Cat LCLo 140 ppm (7 h), inhalation acc. UBA, 1986
Rabbit LCLo 180 ppm (6.5 h), inhalation acc. UBA, 1986
Aquatic organisms:
Goldfish 20 mg/l = lethal acc. UBA, 1986
Small crustaceans 10 mg/l = lethal acc. UBA, 1986

Characteristic effects:

Humans/mammals: The liquid produces severe, poorly healing irritation and burning of the eyes, the respiratory organs, the skin and the gastro-intestinal tract. Deep, painful necroses form on the skin and the mucous membranes. High concentrations cause oedemas of the glottis, larynx and lungs as well as inflammation of the lungs. Poison class 2 (ROTH, 1989). Bromine vapours are even more hazardous as they produce bronchial spasms and pneumonia.

Plants: Bromine is a trace element. Bromides do not damage plants, but are not necessarily required.

ENVIRONMENTAL BEHAVIOUR

Water:
Bromine is denser than water, but dissolves slightly in water and colours it brown. This is followed by the generation of bromine vapours. There is a strong hazard to all types of water, in particular to drinking water, service water and waste water on account of the high toxicity linked to oxidising and corrosive properties. Bromides are found as accompanying ions in potassium and sodium deposits. The bromide content rises with increasing salinity. In coastal areas, higher bromide concentrations in the groundwater can be attributed to the infiltration of seawater. Water hazard class 2 (ROTH, 1989). Bromine prevents the formation of algae in water.

Air:
The liquid readily evaporates and forms caustic vapours. The vapours are denser than air and creep along the ground.

ENVIRONMENTAL STANDARDS

Medium/acceptor Sector Country/organ.

Status

Value Cat. Remarks Source
Soil:   NL

G

20 mg/kg AD     acc. KLOKE, 1988
  NL

G

50 mg/kg AD   Investigation acc. KLOKE, 1988
  NL

G

300 mg/kg AD   Rehabilitation acc. KLOKE, 1988
Air: Workp D

L

0.1 ml/m3 MAK   DFG, 1989
Workp USA

(L)

0.7 mg/m3 TWA   acc. ACGIH, 1986
Workp USA

(L)

2 mg/m3 STEL   acc. UBA, 1986
Workp SU

(L)

0.075 ml/m3     acc. UBA, 1986
Workp SU

(L)

1 mg/m3   Skin resorption acc. KETTNER, 1979
Emiss. D L 5 mg/m3   mass flow > 50 g/h acc. TA Luft, 1986

Comparison/reference values

Medium/origin Country Value Source
Seawater   0.065 kg/m3 acc. ULLMANN, 1978
Fly ash (coal) USA 0.3-21 mg/kg acc. HOCK, 1988
Plants   15 mg/kg acc. HOCK, 1988

Assessment/comments

The biological action of bromine and its compounds is quite similar to that of chlorine and its compounds. However, most bromine compounds are more toxic than the corresponding chlorine compounds while chlorine itself is more hazardous than bromine because of its reactivity.


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