Water Conditioning, Pool

Detergent, Cosmetic

Agriculture, Food, Pharmaceutical

Textile, Leather, Paper

Plastic, Rubber, Polymer

Construction, Mining, Metal

Sectoral Paint, Dye Colorant

Industrial Textiles and Coatings

Vowen, Knitted Fabric

Do you have questions?

We unleash your business potential by maximize the business innovation.

Send Email

+905326357997

Chlorine Gas, Chlorine, Liquefied Chlorine, Dichlorine, Bertholite, 7782-50-5

CHLORINE GAS (Cl₂)

1. Chemical Identity and Material Classification

Chemical Name: Chlorine, Molecular Chlorine
Synonyms: Liquefied Chlorine, Chlorine Gas, Dichlorine, Bertholite
CAS Number: 7782-50-5
Molecular Formula: Cl₂
Molecular Weight: 70.91 g/mol
EC Number: 231-959-5
UN Number: 1017 (Poisonous gas)
RTECS Number: FO2100000
DOT Hazard Class: 2.3 (Toxic gas), Hazard Zone B

2. Physical Properties

2.1 General Physical Properties

Property	Value
Appearance (gas)	Yellow-green gas
Appearance (liquid)	Clear, yellow-green to amber liquid
Odor	Highly pungent, bleach-like (detectable at 0.02–3.4 ppm, mean 0.08 ppm)
Density (gas, 0°C, 1 atm)	3.214 g/L (approx. 2.48 times heavier than air)
Density (liquid, 0°C)	1.468 g/cm³ (1.468 × density of water)
Density (liquid, -35°C)	1.5649 g/cm³
Melting point	-101°C (-149.8°F)
Boiling point	-34°C (-29.2°F)
Critical temperature	144°C (291°F)
Critical pressure	76.1 atm (7.71 MPa)
Critical density	0.573 g/cm³
Vapor pressure (20°C)	4,800 mmHg (6.4 bar / 640 kPa)
Vapor density (air = 1)	2.48
Refractive index (liquid)	1.375
Electrical resistivity (liquid, 20°C)	1 × 10⁹ Ω·cm
log P (octanol/water)	-0.85 (at 20°C)

2.2 Thermal Properties

Parameter	Value
Enthalpy of vaporization (at boiling point)	20.41 kJ/mol (288 kJ/kg)
Enthalpy of fusion	6.41 kJ/mol (90.4 kJ/kg)
Specific heat capacity (C_p, gas, 25°C)	0.479 J/(g·K)
Specific heat capacity (C_p, liquid, -34°C)	0.946 J/(g·K)
Thermal conductivity (gas, 25°C)	0.0089 W/(m·K)
Gas expansion ratio	1 L liquid → 456–460 L gas (at 20°C, 1 atm)

3. Chemical Properties and Reactivity

3.1 Basic Chemical Characteristics

Oxidation state: 0 (elemental chlorine)
Electron affinity: 349 kJ/mol (highest among halogens after fluorine)
Electronegativity (Pauling): 3.16 (third highest, after fluorine 3.98 and oxygen 3.44)
Bond dissociation energy (Cl–Cl): 242.6 kJ/mol (relatively low → high reactivity)
Standard reduction potential (Cl₂ + 2e⁻ → 2Cl⁻): +1.358 V (vs. SHE)

3.2 Reactivity with Water

Parameter	Value
Solubility in water (0°C)	1.46 g/100 mL (14.6 g/L)
Solubility in water (20°C)	0.73 g/100 mL (7.3 g/L)
Solubility in water (30°C)	0.57 g/100 mL (5.7 g/L)
Solubility in water (60°C)	0.33 g/100 mL (3.3 g/L)
Hydrolysis reaction	Cl₂ + H₂O → HOCl + HCl (hypochlorous acid + hydrochloric acid)
Equilibrium constant (K, 25°C)	4.5 × 10⁻⁴
Dissolved species at pH 7	Cl₂, HOCl (~75%), OCl⁻ (~25%)

3.3 Reactivity with Other Substances

Substance	Reaction	Hazard
Hydrogen (H₂)	2H₂ + Cl₂ → 2HCl (explosive in sunlight/UV)	Explosion
Hydrocarbons	Substitution/addition reactions (exothermic)	Fire/explosion
Ammonia (NH₃)	3Cl₂ + 2NH₃ → N₂ + 6HCl	Toxic fumes
Acetylene (C₂H₂)	Forms explosive chloroacetylenes	Severe explosion
Metals (Al, Ti, Fe, Cu, Zn)	Metal chloride formation (exothermic, may be pyrophoric)	Fire, corrosion
Alkalis (NaOH, KOH)	Cl₂ + 2OH⁻ → OCl⁻ + Cl⁻ + H₂O	Exothermic
Reducing agents	Strong reaction	Fire/explosion
Organic compounds	Chlorination (violent at elevated temperatures)	Fire/explosion

4. Production Methods

4.1 Electrolysis of Brine (Chlor-Alkali Process – Primary Industrial Method)

Reaction: 2NaCl + 2H₂O → 2NaOH + Cl₂ + H₂
Process: Electrolysis of saturated sodium chloride solution
Cell types:
- Mercury cell (diaphragm-free, declining)
- Diaphragm cell (asbestos/PTFE diaphragm)
- Membrane cell (modern standard – ion-exchange membrane)
Current efficiency: 95–98%
Power consumption: 2,500–3,000 kWh/ton Cl₂
Co-products: Sodium hydroxide (NaOH) and hydrogen (H₂)

4.2 Historical Methods (Obsolete)

Scheele's method (1774): 4HCl (conc.) + MnO₂ → MnCl₂ + 2H₂O + Cl₂↑
Deacon process (gas phase): 4HCl + O₂ ⇌ 2Cl₂ + 2H₂O (with CuCl₂ catalyst, 450°C) – limited use

4.3 Liquefaction for Liquid Chlorine

Process: Chlorine gas from electrolysis → drying (H₂SO₄) → compression → cooling to -25 to -35°C → liquefaction
Refrigerant: Calcium chloride brine or ammonia evaporator
Liquefaction pressure (20°C): 6.4 bar (abs)
Storage: Liquid chlorine in cylinders, drums, tank cars, or storage tanks

5. Thermodynamic Properties

Parameter	Value
Standard enthalpy of formation (ΔH_f°)	0 kJ/mol (reference state)
Standard Gibbs free energy (ΔG_f°)	0 kJ/mol
Standard entropy (S° at 298 K)	223.1 J/(mol·K)
Heat of vaporization (ΔH_vap)	20.41 kJ/mol
Heat of fusion (ΔH_fus)	6.41 kJ/mol
Adiabatic flame temperature (with H₂)	~2,200°C

6. Toxicological Profile and Health Hazards

6.1 Acute Toxicity

Parameter	Value
LC₅₀ (rat, 1 hour inhalation)	293 ppm
LC₅₀ (mouse, 1 hour inhalation)	137 ppm
LC₅₀ (human, 30 min)	~50–100 ppm (estimated lethal)
Immediate health effects (1–3 ppm)	Eye/nose/throat irritation
Moderate effects (5–15 ppm)	Coughing, chest tightness, dyspnea
Severe effects (15–30 ppm)	Pulmonary edema, chemical pneumonitis
Rapidly fatal (>30–50 ppm)	Respiratory failure, death within 30–60 min
IDLH (Immediately Dangerous to Life and Health)	10 ppm (NIOSH)

6.2 Odor Threshold and Detection

Parameter	Value
Odor threshold (pungent, bleach-like)	0.02–3.4 ppm (mean 0.08 ppm)
Eye irritation threshold	0.5–1 ppm
OSHA PEL (ceiling)	1 ppm (3 mg/m³)
ACGIH TLV (TWA)	0.5 ppm (1.5 mg/m³)
NIOSH REL (ceiling, 15 min)	0.5 ppm
NIOSH IDLH	10 ppm
MSHA permissible limit	1 ppm (TWA)

6.3 Mechanism of Toxicity

Primary target: Respiratory tract (nose, pharynx, larynx, trachea, bronchi, alveoli)
Mechanism: Cl₂ + H₂O → HOCl + HCl → corrosive acid formation in moist mucous membranes → oxidative damage to epithelial cells → pulmonary edema
Delayed effects: Reactive airway dysfunction syndrome (RADS), chronic bronchitis, reduced lung function

7. Health Effects and Medical Management

7.1 Symptoms by Exposure Level

Concentration (ppm)	Symptoms
0.02–3.4	Detectable odor
0.5–1	Mild eye/nose/throat irritation
1–3	Moderate mucous membrane irritation
3–5	Chest tightness, cough, dyspnea on exertion
5–15	Severe coughing, choking sensation, substernal pain
15–30	Immediate dyspnea, chemical pneumonitis, pulmonary edema
30–50	Potentially fatal within 30–60 minutes
>50	Rapidly fatal (respiratory arrest)

7.2 Chronic Effects

Occupational asthma (reactive airways dysfunction syndrome)
Chronic bronchitis and reduced forced expiratory volume (FEV₁)
Dental erosion (long-term exposure)
Possible increased risk of lung cancer (limited evidence, IARC Group 3)

7.3 Emergency Medical Response

Action	Procedure
Rescue	Move victim to fresh air immediately (use SCBA for rescuer)
Respiratory support	Administer 100% oxygen if breathing is difficult
Severe cases	Intubation and mechanical ventilation may be required
Pulmonary edema management	Positive pressure ventilation (PEEP/CPAP), corticosteroids
Eye exposure	Irrigate with water for at least 15 minutes
Skin exposure (liquid)	Remove contaminated clothing, flush with copious water
Prohibited	Do NOT give epinephrine (may exacerbate arrhythmias in hypoxic patients)

8. Industrial Applications

8.1 Water and Wastewater Disinfection (Primary Application)

Parameter	Value
Application	Disinfection of drinking water, swimming pools, wastewater
Typical dosage (drinking water)	1–4 mg/L (as Cl₂)
Contact time	30–60 minutes
Residual chlorine (free)	0.2–0.5 mg/L at point of use
CT value (Cryptosporidium inactivation)	1,000–10,000 mg·min/L (ineffective – UV or ozone preferred)
By-products	Trihalomethanes (THMs), haloacetic acids (HAAs), chloramines

8.2 Bleaching (Pulp and Paper, Textile)

Application	Description
Pulp bleaching	Elemental chlorine-free (ECF) bleaching now dominant; Cl₂ used for chlorine bleaching (declining)
Textile bleaching	Bleaching of cotton and linen (historically important, now largely replaced by hypochlorite or H₂O₂)

8.3 Chemical Synthesis (Largest Use: ~70% of chlorine production)

Product	Application	Chlorine Consumption
PVC (polyvinyl chloride)	Pipes, siding, wire insulation, medical devices	~40% of Cl₂ production
MDI/TDI (polyurethanes)	Foams, adhesives, coatings	~10%
Epichlorohydrin (ECH)	Epoxy resins	~5%
Chlorinated solvents	Degreasers, dry cleaning (declining)	~10%
Chlorinated intermediates	Pharmaceuticals, agrochemicals, dyes	~15%
Titanium dioxide (TiO₂, chloride process)	Pigments, paints	~10%
Chlorinated methanes (CH₂Cl₂, CHCl₃, CCl₄)	Refrigerants, solvents (regulated)	Declining

8.4 Metallurgy and Ore Processing

Application	Description
Titanium production	Cl₂ + TiO₂ + C → TiCl₄ → Ti (Kroll process)
Magnesium production	Cl₂ + MgO + C → MgCl₂ → Mg (electrolysis)
Gold extraction	Used in chlorination leaching (historical, replaced by cyanide)
Rare earth processing	Chlorination of rare earth oxides to chlorides

8.5 Disinfection and Sanitization

Application	Description
Drinking water treatment	Primary disinfectant (kills bacteria, viruses)
Swimming pools	Continuous chlorination (HOCl as active agent)
Wastewater disinfection	Effluent disinfection before discharge
Food processing	Sanitization of fruits, vegetables, poultry chill water
Cooling towers	Biofouling control (algicide/bactericide)

9. Safe Handling and Storage

9.1 Material Compatibility

Material	Compatibility with Cl₂ (dry, gas/liquid)
Carbon steel	Suitable (dry Cl₂ only, below 200°C)
Stainless steel (304, 316)	Suitable (dry Cl₂)
Titanium	NOT suitable (pyrophoric reaction)
Aluminum	NOT suitable (violent reaction)
Copper	Suitable (dry) but forms CuCl₂ if moist
PTFE / Teflon	Excellent
PVC	Suitable (ambient temperature)
Natural rubber	NOT suitable (degradation)
Water	Highly reactive (forms HOCl + HCl)

9.2 Storage Requirements

Parameter	Requirement
Container types	Steel cylinders (50 kg, 500 kg, 1,000 kg), ton containers (1,000 lb), tank cars (15–90 tons), storage tanks
Storage temperature	Ambient (but not above 50°C)
Ventilation	Continuous mechanical exhaust at low level (Cl₂ heavier than air)
Detection	Continuous chlorine gas detectors with audible/visual alarms (set at 0.5 ppm)
Isolation	Separate from incompatible materials (acetylene, hydrogen, ammonia, metal powders, reducing agents)
Secondary containment	Required for liquid Cl₂ storage
Signs	"Poison – Inhalation Hazard" and "Non-flammable Gas" (Class 2.3)

9.3 Inspection and Testing

Component	Frequency	Test Method
Cylinders	5 years (minimum)	Hydrostatic test, ultrasonic thickness measurement
Valves	Per use	Leak check with ammonia vapor or soap solution
Piping systems	Annually	Visual, ultrasonic, leak detection
Pressure relief devices	Annually	Calibration verification

10. Personal Protective Equipment (PPE)

10.1 Minimum PPE for Handling

Equipment	Specification
Respiratory protection	Self-contained breathing apparatus (SCBA) or airline respirator with full facepiece (mandatory for >1 ppm)
Chemical protective suit	Full-body, acid-resistant (butyl rubber or neoprene)
Gloves	Butyl rubber, neoprene, or Viton (minimum 0.5 mm thickness)
Eye protection	Chemical splash goggles plus full face shield
Footwear	Steel-toed rubber boots (chemical resistant)

10.2 Emergency Equipment

Deluge showers and eyewash stations – within 10 seconds of handling area
SCBA – readily accessible, inspected monthly
Chlorine emergency kit ("C-Kit", "B-Kit") – for cylinder leak containment
Ammonia vapor or NH₄OH solution – for leak detection (produces white smoke of NH₄Cl)

11. Leak Detection and Emergency Response

11.1 Leak Detection Methods

Method	Sensitivity	Notes
Odor	0.02–3.4 ppm	Unreliable (olfactory fatigue occurs rapidly)
Ammonia vapor (NH₃)	Moderate	Produces dense white smoke (NH₄Cl) – do NOT use inside, toxic
Potassium iodide (KI) solution	0.5 ppm	Impregnated paper turns blue-black
Electrochemical sensors	0.1 ppm	Continuous monitoring, preferred method
UV-visible photometry	0.1 ppm	Fixed-point analyzers

11.2 Emergency Response (Small Leak – Cylinder)

Step	Action
1	Evacuate area – isolate for 200–500 m downwind
2	Wear full SCBA and protective suit
3	Identify leak location (ammonia vapor – do NOT use inside occupied spaces)
4	Rotate cylinder so leak is at top (vapor phase)
5	Apply chlorine emergency kit (C-Kit) – contain leak
6	Move cylinder to outdoor ventilated area or gas destruction system

11.3 Large Leak or Tank Release

Immediate actions: Evacuation of 1–3 km radius downwind (depending on quantity, weather)
Respiratory protection: Full SCBA mandatory
Containment: Water spray to knock down chlorine gas (forms HOCl/HCl, runoff is corrosive) – do NOT apply to liquid chlorine pool
Dispersion: Chlorine gas is heavier than air; it travels along ground into low-lying areas
Notification: Local emergency planning committee (LEPC), fire department, environmental agency

12. Environmental Fate and Ecotoxicity

Parameter	Value
Aquatic toxicity (fish, LC₅₀, 96 hours)	0.05–0.5 mg/L (as residual chlorine)
Daphnia magna (EC₅₀, 48 hours)	0.01–0.1 mg/L
Algal toxicity (EC₅₀, 72 hours)	0.01–0.1 mg/L
Ozone depletion potential	0.005 (very low – but degrades stratospheric ozone)
Atmospheric lifetime	~1–2 days (reactive)
Degradation in atmosphere	Photodissociation: Cl₂ + hν → 2Cl·
Effect on stratospheric ozone	Cl· + O₃ → ClO· + O₂ → catalytic ozone destruction
Drinking water residual limit	0.2–0.5 mg/L (free chlorine)
Wastewater discharge limit	<0.1–0.5 mg/L (depending on jurisdiction)

13. Fire and Explosion Hazards

Parameter	Value
Flash point	Not applicable (non-flammable gas)
Autoignition temperature	Not applicable (supports combustion)
Fire hazard	Not flammable, but supports combustion (strong oxidizer)
Explosion hazard	Forms explosive mixtures with hydrogen, acetylene, hydrocarbons, metal powders, ammonia
Combustible materials	Chlorine can ignite or explode on contact (e.g., turpentine, diethyl ether, phosphine)
Special firefighting	Do NOT apply water to liquid chlorine pool (violent reaction, toxic gas release). Use water spray to cool containers (from distance). Evacuate immediately. SCBA required.

14. Transport Information

Regulation	Classification
UN Number	1017
Proper shipping name	Chlorine
DOT hazard class	2.3 (Poisonous gas)
Hazard Zone	B (gases poisonous by inhalation)
Subsidiary hazard	5.1 (Oxidizer – not consistently assigned, but recognized)
Label(s)	Poison gas, Non-flammable gas
Packing group	Not applicable (gas)
Marine pollutant	Yes (USA; not under MARPOL Annex III)
Special provisions	T43 (portable tanks), T50 (low pressure tanks)

15. Regulatory Information

Regulation	Classification / Requirement
OSHA PEL	Ceiling = 1 ppm (3 mg/m³)
ACGIH TLV	TWA = 0.5 ppm (1.5 mg/m³), STEL = 1 ppm
NIOSH REL	Ceiling = 0.5 ppm (15 min)
IDLH	10 ppm
EPA EPCRA (SARA Title III)	Extremely Hazardous Substance (EHS) – TPQ = 100 lb (45 kg)
EPA RMP (40 CFR 68)	Regulated – threshold 2,500 lb (1,134 kg)
EPA CAA	Hazardous Air Pollutant (HAP)
Clean Water Act	Priority pollutant (residual chlorine)
EU CLP Regulation	Hazard class: Acute Tox. 2 (H330), Skin Corr. 1A (H314), Ox. Gas 1 (H270), Aquatic Acute 1 (H400)
IARC carcinogenicity	Group 3 (not classifiable) – inadequate evidence in humans

16. First Aid Measures

Exposure Route	Immediate Action
Inhalation	Remove to fresh air; administer 100% oxygen; if breathing stops, give artificial respiration (avoid mouth-to-mouth – use pocket mask); seek immediate medical attention
Eye contact	Irrigate with copious water for at least 15 minutes, lifting eyelids; seek ophthalmological evaluation
Skin contact (gas)	Flush with water; remove contaminated clothing (may adhere to skin)
Skin contact (liquid)	Do NOT rub; flood with water for at least 15 minutes; seek medical attention (cold burns/frostbite)
Ingestion	Very unlikely (gas/liquid); if liquid chlorine ingested, do NOT induce vomiting; dilute with milk or water; seek emergency medical attention

17. Storage Code and Shelf Life

Parameter	Requirement
Storage temperature	Ambient (10–40°C) – avoid temperatures >50°C
Pressure	Containers designed for vapor pressure at ambient temperature
Shelf life	Indefinite in sealed cylinders (product does not degrade)
Cylinder inspection	Hydrostatic testing every 5–10 years (depending on jurisdiction)

18. Synonyms and Common Names

English: Chlorine gas, Liquefied chlorine, Molecular chlorine, Dichlorine, Bertholite
French: Chlore, Chlore liquéfié
German: Chlor, Flüssigchlor, Chlorgas
Spanish: Cloro, Cloro líquido
Italian: Cloro, Cloro liquido
Turkish: Klor gazı, Sıvı klor

19. Why Choose Chlorine? (Technical Summary)

Advantage	Description
Proven efficacy as disinfectant	Kills bacteria, viruses, and protozoa (except Cryptosporidium)
Residual disinfection	Free chlorine residual prevents recontamination in distribution systems
Low cost	Most economical large-scale disinfectant (cost ~$0.10–0.30/kg Cl₂)
Well-established production	Chlor-alkali industry produces >70 million metric tons annually
Versatile chemical intermediate	Essential for PVC, polyurethanes, epoxies, solvents, agrochemicals
Oxidizing power (E° = 1.36 V)	Effective for bleaching, wastewater oxidation, metal extraction
High gas expansion ratio	1 L liquid → 456 L gas at 20°C (efficient storage/transport)
Readily analyzable	Simple DPD colorimetric test, amperometric titration, etc.
Multiple application forms	Gas, liquid (compressed), hypochlorite solutions, chlorine dioxide (derived)
Limitation note:	Highly toxic and corrosive – requires rigorous safety protocols (SCBA, leak detection, emergency planning). Forms toxic by-products (THMs, HAAs) in water treatment. Alternative disinfectants (ozone, UV, chlorine dioxide) are gaining share where by-products are regulated.

20. Sectoral Suitability Summary Table

Sector	Application	Typical Concentration	Alternatives
Drinking Water	Primary disinfection	1–4 mg/L residual	Ozone, UV, chloramines, chlorine dioxide
Swimming Pools	Sanitization, oxidation	1–3 mg/L free chlorine	Bromine, ozone, UV, salt chlorine generators
Wastewater	Effluent disinfection	5–15 mg/L (contact)	UV, ozone, peracetic acid
Pulp & Paper	Bleaching (ECF – elemental chlorine-free)	Historical; now largely ClO₂, H₂O₂, O₂	Chlorine dioxide, oxygen, hydrogen peroxide, ozone
Chemical Industry	PVC production (via EDC, VCM)	Largest use (~40% of Cl₂)	None (feedstock essential)
Metallurgy	Ti, Mg production	Process gas	None (essential)
Food Processing	Poultry, produce sanitization	5–20 ppm (wash water)	Peracetic acid, ozone, UV
Cooling Towers	Biofouling control	0.5–1 mg/L residual	Bromine, chlorine dioxide, non-oxidizing biocides
Textile	Bleaching (historical)	Declining	H₂O₂, sodium hypochlorite

This TDS is prepared in compliance with ISO 11014-1 format and is intended for water treatment plant operators, chemical process engineers, safety professionals, industrial hygienists, emergency responders, and procurement specialists. Safety Data Sheets (SDS), emergency response plans, and chlorine handling training materials are available upon request.

Chlorine Gas, Chlorine, Liquefied Chlorine, Dichlorine, Bertholite, 7782-50-5