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DESIGNATIONS
CAS No.: 7782-50-5
Registry name: Chlorine
Chemical name: Chlorine
Synonyms, Trade names: Chlorum
Chemical name (German): Chlor
Chemical name (French): Chlore
Appearance: greenish-yellow gas with pungent irritating odour
BASIC CHEMICAL AND PHYSICAL DATA
| Empirical formula: | Cl2 |
| Rel. molecular mass: | 70.91 g |
| Density: | 0.567 g/cm3 (liquid, critical density at 144 °C); 3.21 g/l (gas) at 0°C, 1013 hPa |
| Relative gas density: | 2.49 |
| Boiling point: | -34.05°C |
| Melting point: | -100.98°C |
| Vapour pressure: | 6.8 bar at 20°C |
| Odour threshold: | 0.05 ppm |
| Solvolysis/solubility: | in water: 7.3 g/l at 20°C |
| in tetrachloromethane: 176.5 g/l at 19°C | |
| Conversion factors: | 1 mg/m3 = 0.339 ml/m3 |
| 1 ml/m3 = 2.947 mg/m3 |
ORIGIN AND USE
Usage:
Chlorine is used for numerous applications in the chemical
industry, for example in the manufacture of chlorinated organic
products (synthetics, solvents, insecticides, herbicides). It is
also used in the cellulose/paper industry and in laundries as a
bleaching agent. Drinking-water and swimming-pool water
disinfection is a further application.
Origin/derivation:
In nature, chlorine is chiefly found as chloride (bonded to
sodium, potassium and magnesium). A further important chlorine
compound is hydrogen chloride. Nowadays, chlorine is primarily
produced by electrolysis of alkali-metal chlorides (mercury
method and diaphragm method). Use is also still made of chemical
methods (SHELL chlorine method, KEL chlorine process, SOUTHWEST
POTASH method).
Production figures (worldwide):
1975 = 22.5 million tons; 1983 = 30 million tons; 1994 =
>40 million tons
Toxicity
| Humans: | LCLo 837 ppm/30 min, inhalation | acc. UBA, 1986 |
| 2.5 mg/l air = immediately lethal | acc. TAB. CHEMIE, 1980 | |
| Mammals: | ||
| Rat | LC50 293 ppm/1 h, inhalation | acc. UBA, 1986 |
| Mouse | LC50 137 ppm/1 h, inhalation | acc. UBA, 1986 |
| Guinea pig | LCLo 330 ppm/7 h, inhalation | acc. UBA, 1986 |
| Dog | LCLo 800 ppm/30 min, inhalation | acc. UBA, 1986 |
| Aquatic organisms: | ||
| Trout | 0.08 ppm/ 168 h/ freshwater; TLm | acc. UBA, 1986 |
| Fish | more than 0.05 mg/l lethal | |
Characteristic effects:
Humans/mammals: Chlorine is an extremely caustic, poisonous gas. Symptoms of poisoning following inhalation are the irritation of the mucous membranes of the respiratory tract combined with breathing difficulties, coughing up of blood and low pulse rate. Humans become accustomed to odour and irritation if exposed for a long time or repeatedly. Symptoms may be delayed. Liquid chlorine is extremely caustic on the skin.
Plants: Any description of the damage to plants generally relates to the chloride impact although chlorine gas is also absorbed by plant leaves and destroys plant tissue partly by oxidation and partly by expulsion of hydrogen in organic compounds.
ENVIRONMENTAL BEHAVIOUR
Water:
Water hazard class 2. Destroys all aquatic life; kills
bacteria as long as free chlorine can be detected. Chlorine
reacts with water forming hydrogen chloride/hydrochloric acid
depending on water content. Chlorine corrodes several materials
when wet.
Air:
On expansion, chlorine gas (compressed gas) forms a cold mist
which is denser than air; poisonous, corrosive mixtures form in
air over the surface of water.
Soil:
Chlorine is only found in soil in ionised form of its salts
(chlorides).
ENVIRONMENTAL STANDARDS
| Medium/acceptor | Sector | Country/organ. | Status |
Value | Cat. | Remarks | Source |
| Air: | D | L |
0.1 mg/m3 | IW 1 | 1) | acc. TA Luft, 1986 | |
| D | L |
0.3 mg/m3 | IW 2 | 2) | acc. TA Luft, 1986 | ||
| D | G |
0.10 mg/m3 | Monthly average, plants | acc. LAU-BW | |||
| Emiss. | D | L | 5 mg/m3 | mass flow > 50 g/h | acc. TA Luft, 1986 | ||
| Workp | D | L |
1.5 mg/m3 | MAK | Peak limit I | DFG, 1989 | |
| Workp | D | L |
1.5 mg/m3 | BAT | acc. LAU-BW | ||
| Workp | DDR | L |
1 mg/m3 | acc. LAB. CHEMIE, 1980 | |||
| Workp | SU | (L) |
1 mg/m3 | acc. SORBE, 1988 | |||
| Workp | USA | (L) |
3 mg/m3 | TWA | acc. SORBE, 1988 | ||
| Workp | USA | (L) |
9 mg/m3 | STEL | acc. SORBE, 1988 |
Notes:
1) Annual arithmetic mean
2) 98 % of annual 30-minute average
Assessment/comments
Chlorine is a hazard to all types of water and in particular to drinking water because of its high toxicity and corrosiveness as well as its oxidising effect. Disaster alarm must be given if large quantities of the gas are liberated.