Hydrochloric Acid, Chlorohydric Acid, Hydrogen Chloride, Muriatic Acid, HCl, 7647-01-0

Hydrochloric Acid, Chlorohydric Acid, Hydrogen Chloride, Muriatic Acid, HCl, 7647-01-0

HYDROCHLORIC ACID (HCL)

Hydrochloric Acid / Muriatic Acid / Chlorohydric Acid / Spirit of Salt / Tuz Ruhu
CAS Number: 7647-01-0
EC Number: 231-595-7

1. IDENTIFICATION INFORMATION

Note: Hydrochloric acid is the aqueous solution of hydrogen chloride gas (HCl) dissolved in water.

2. PHYSICAL PROPERTIES

3. CHEMICAL PROPERTIES

HCl + H₂O → H₃O⁺ + Cl⁻ (complete dissociation)

Neutralization Reaction (with Base):

HCl + NaOH → NaCl + H₂O

Reaction with Metal (Zinc):

2 HCl + Zn → ZnCl₂ + H₂↑

Reaction with Carbonate (Calcium Carbonate):

2 HCl + CaCO₃ → CaCl₂ + CO₂↑ + H₂O

4. PRODUCTION PROCESS

Reaction Equation (Chlorine-Hydrogen Combustion - Most Common):

H₂ + Cl₂  —[combustion]—> 2 HCl (gas)
HCl (gas) + H₂O → HCl (aqueous solution)

Reaction Equation (Salt and Sulfuric Acid - Traditional):

2 NaCl + H₂SO₄ + Heat → Na₂SO₄ + 2 HCl↑

Typical Commercial Grades:

5. AVAILABLE FORMS AND SPECIFICATIONS

Typical Specifications (ACS Grade, 36.5-38.0%):

Typical Specifications (Semiconductor Grade, 30-37%):

6. APPLICATIONS

6.1. Steel and Metal Industry – Largest Use (~50%)

Reaction (Rust Removal - Pickling):

Fe₂O₃ (rust) + 6 HCl → 2 FeCl₃ + 3 H₂O
Fe₃O₄ (scale) + 8 HCl → FeCl₂ + 2 FeCl₃ + 4 H₂O

6.2. Chemical Synthesis – Second Largest Use (~25%)

6.3. Oil and Gas Industry

Reaction (Acidizing - Limestone Dissolution):

CaCO₃ + 2 HCl → CaCl₂ + CO₂↑ + H₂O

6.4. Food Processing Industry

6.5. Water Treatment

6.6. Pharmaceutical Industry

6.7. Leather Tanning

6.8. Textile Industry

6.9. Semiconductor and Electronics Industry

6.10. Laboratory and Analytical Applications

6.11. Other Applications

7. CONCENTRATION GUIDELINES BY APPLICATION

8. SAFETY AND HEALTH INFORMATION (GHS CLASSIFICATION)

9. HAZARD STATEMENTS (H-CODES)

10. SAFETY STATEMENTS (P-CODES)

11. TOXICOLOGICAL INFORMATION

Health Effects:

Occupational Exposure Limits:

12. FIRST AID MEASURES

13. FIRE FIGHTING MEASURES

14. ENVIRONMENTAL INFORMATION

15. STORAGE AND HANDLING

Handling Notes:

• Always add acid to water, NEVER add water to acid (prevents violent splattering)

• Use only in well-ventilated areas or under fume hood

• Use chemical goggles, face shield, acid-resistant gloves (neoprene, butyl rubber, nitrile), and acid-resistant apron

• Store bottles in a sealed plastic bag to prevent corrosion of storage area labels and metal surfaces

• Label spray (Krylon) on bottle labels helps preserve them from fume damage

• Use secondary containment (tray) for storage

• Have emergency eyewash stations and safety showers nearby

• Do not store near formaldehyde (forms chloromethyl methyl ether - carcinogen)

16. TRANSPORT INFORMATION

Hydrogen Chloride (Anhydrous Gas):

17. REGULATORY INFORMATION

Food Additive Status: E507 (EU) – acidity regulator, permitted in food processing

FDA Status: GRAS for certain food applications

EPA Registration: Registered as antimicrobial pesticide

18. OTHER NAMES AND SYNONYMS

Database Identifiers:

19. COMMONLY ASKED QUESTIONS (FAQ)

Q1. What is the difference between hydrochloric acid and hydrogen chloride?

Hydrogen chloride (HCl) is a colorless gas at room temperature. Hydrochloric acid is the aqueous solution of hydrogen chloride gas dissolved in water. The gas is classified as a toxic gas (UN 1050), while the solution is classified as a corrosive liquid (UN 1789).

Q2. What is the maximum concentration of hydrochloric acid available?

The azeotropic concentration of hydrochloric acid is approximately 20.2% at 108°C. However, commercially available concentrated HCl is 36.5-38% (ACS grade) and 30-37% (technical grade). Higher concentrations are not practical because HCl gas escapes from solution. Fuming hydrochloric acid (37%) releases HCl gas when exposed to air, forming dense white fumes.

Q3. Why does hydrochloric acid fume?

Concentrated hydrochloric acid (above 30%) releases hydrogen chloride gas from the surface when exposed to air. The HCl gas reacts with atmospheric moisture to form a visible mist of hydrochloric acid droplets, creating the characteristic white fumes. This is why it is called "fuming" hydrochloric acid.

Q4. How should hydrochloric acid be stored safely?

Store in a cool, dry, well-ventilated area in tightly closed, corrosion-resistant containers (glass, HDPE, PVC, rubber-lined steel). Keep away from strong bases, oxidizing agents, and metals. Store in a dedicated acid cabinet. To prevent corrosion of labels and metal cabinets, place bottles in a sealed plastic bag. Never store near formaldehyde.

Q5. Why should I add acid to water, not water to acid?

Adding acid to water is always safer because:

• The heat of dilution is dissipated by the large volume of water

• If splashing occurs, it is primarily water with a small amount of acid

• Adding water to concentrated acid causes localized boiling and violent splattering of concentrated acid

Q6. What materials are compatible with hydrochloric acid?

Compatible: Glass, HDPE, PTFE, PVC, CPVC, FRP, rubber-lined steel, tantalum, titanium, silicon rubber, Viton.
Incompatible: Carbon steel, stainless steel (some grades), aluminum, magnesium, zinc, copper alloys (especially at high temperatures).

Q7. How should hydrochloric acid spills be handled?

• Evacuate area and ensure adequate ventilation

• Wear appropriate PPE (acid-resistant suit, gloves, goggles, SCBA)

• Contain spill with inert absorbent (vermiculite, sand, diatomaceous earth)

• Neutralize with sodium bicarbonate (baking soda), sodium carbonate, or calcium carbonate

• After neutralization, collect and dispose as hazardous waste

• For small spills, dilute with large quantities of water (if local regulations permit)

Q8. What are the signs of hydrochloric acid exposure?

• Inhalation: Coughing, choking, nosebleeds, shortness of breath, chest tightness, pulmonary edema

• Skin: Burning pain, redness, blistering, ulceration (depends on concentration)

• Eyes: Severe pain, tearing, redness, blurred vision, potential blindness

• Ingestion: Burning mouth/throat, nausea, vomiting, abdominal pain, throat swelling

Q9. What is "spent acid" and how is it handled?

Spent acid is used hydrochloric acid that has been contaminated during metal pickling or other industrial processes. It contains dissolved metal ions (FeCl₂, FeCl₃, ZnCl₂, etc.). Spent acid must be:

• Regenerated (thermal or membrane processes to recover HCl)

• Neutralized and precipitated as metal hydroxides for disposal

• Treated in wastewater treatment facilities

Q10. Is hydrochloric acid regulated as a hazardous air pollutant?

Yes. Hydrogen chloride gas (including emissions from hydrochloric acid) is listed as a Hazardous Air Pollutant (HAP) under the Clean Air Act in the US and similar regulations internationally. Facilities must control and monitor emissions. The threshold for reporting is 10 tons per year for hydrogen chloride (anhydrous).

20. SUMMARY AND IMPORTANT WARNINGS

SUMMARY:

Hydrochloric acid (HCl, CAS 7647-01-0) is a strong mineral acid consisting of hydrogen chloride gas dissolved in water. It is a clear, colorless to pale yellow liquid with a sharp, pungent odor. It is completely miscible with water and fully dissociates into H⁺ and Cl⁻ ions, making it a very strong acid with pKa = -7. The most common commercial concentrations are 30-38% by weight. As one of the most widely produced industrial chemicals, hydrochloric acid has numerous applications, with the largest use being steel pickling (removal of rust and scale), followed by chemical synthesis (production of vinyl chloride for PVC, metal chlorides, and organic chlorides). Other major applications include oil well acidizing (dissolving limestone formations), food processing (corn syrup production, food additive E507), water treatment (pH adjustment, demineralization regeneration), pharmaceutical synthesis (pH regulation, hydrochloride salt formation), leather tanning, textile processing, semiconductor manufacturing (wafer cleaning), and laboratory analytical work.

Key Properties:

Main Application Areas:

Key Safety Points:

• CORROSIVE: Causes severe skin burns and eye damage (H314, H318)

• TOXIC: Toxic if swallowed or inhaled (H301, H302, H330, H331)

• RESPIRATORY SENSITIZER: May cause allergy or asthma symptoms (H334)

• METAL CORROSIVE: May be corrosive to metals (H290)

• NON-FLAMMABLE: But reacts with metals to produce flammable hydrogen gas

• FUMING: Concentrated solutions release corrosive HCl gas (use ventilation)

• ALWAYS ADD ACID TO WATER: Never add water to acid

• USE VENTILATION: Work in fume hood or well-ventilated area

• USE PPE: Chemical goggles, face shield, acid-resistant gloves (neoprene, butyl, nitrile), acid-resistant apron, rubber boots

• STORAGE: Dedicated acid cabinet, secondary containment, away from bases and oxidizing agents

IMPORTANT WARNINGS:

Concentration Hazards: The hazards of hydrochloric acid are concentration-dependent. Concentrations above 10% are classified as corrosive, while lower concentrations (2-10%) are classified as irritants. Concentrated HCl (36-38%) also poses a significant inhalation hazard due to fuming (release of HCl gas). Always check Safety Data Sheet for specific concentration.

Fuming Hazard: Concentrated hydrochloric acid (above 30%) releases hydrogen chloride gas when exposed to air. The gas reacts with atmospheric moisture to form a visible mist of hydrochloric acid droplets. This mist is corrosive to the respiratory tract, metal surfaces, and equipment. Always handle under a fume hood or with adequate ventilation.

Always Add Acid to Water (Never Water to Acid): When diluting hydrochloric acid, ALWAYS add acid to water slowly with stirring. NEVER add water to concentrated acid. Adding water to acid causes localized boiling and violent splattering due to the heat of dilution (exothermic). Adding acid to water allows the large volume of water to absorb the heat safely.

Storage Compatibility: Store hydrochloric acid in dedicated acid storage cabinets. To prevent corrosion of metal cabinets and labels, store bottles in tightly sealed plastic bags. NEVER store near formaldehyde (formaldehyde + HCl reacts to produce bis(chloromethyl) ether, a potent carcinogen). Never store near strong bases, oxidizing agents, or metals (hydrogen gas production).

Metal Reaction: Hydrochloric acid reacts with many metals (aluminum, magnesium, zinc, iron, carbon steel) to produce flammable and potentially explosive hydrogen gas (H₂). Do not store or use hydrochloric acid in metal containers (except certain corrosion-resistant alloys like tantalum, titanium, and Hastelloy). Use plastic (HDPE, PVC, CPVC) or glass containers.

Medical Emergency: Hydrochloric acid causes severe chemical burns. In case of skin contact, remove contaminated clothing immediately and flush with water for at least 15 minutes. Do not attempt to neutralize with bases (this can generate heat and worsen burns). For eye contact, flush immediately with water for 15-20 minutes. For ingestion, do NOT induce vomiting (vomiting causes additional esophageal damage). For inhalation, move to fresh air immediately. Seek immediate medical attention for all significant exposures.

Ventilation Requirements: Due to the release of corrosive HCl gas (fuming) from concentrated solutions, hydrochloric acid must be handled under adequate local exhaust ventilation (fume hood) or in a well-ventilated area. Long-term exposure to low concentrations of HCl vapor can cause dental erosion, chronic bronchitis, and respiratory sensitization (occupational asthma).

Spill Response: In case of spill:

1. Evacuate area and ensure adequate ventilation

2. Wear full PPE (acid-resistant suit, boots, gloves, SCBA)

3. Contain spill with inert absorbent (sand, vermiculite, diatomaceous earth)

4. Neutralize with sodium bicarbonate (baking soda) or sodium carbonate (soda ash) – this will produce CO₂ gas (effervescence)

5. After neutralization (pH 6-9), dispose as hazardous waste

6. For large spills, contact emergency response and environmental authorities

Corrosive to Metals: Hydrochloric acid is corrosive to many metals, including carbon steel, stainless steel (some grades), aluminum, copper, brass, and zinc. Even acid vapor (fumes) causes rapid corrosion of metal storage cabinets, shelving, electrical equipment, and structural components. Use plastic, glass, or corrosion-resistant alloys for storage and handling.

Inhalation Hazard - Sensitization: Repeated inhalation exposure to HCl mist or vapor can cause respiratory sensitization (occupational asthma). Some individuals may develop allergic-type reactions (bronchospasm, wheezing, shortness of breath) upon subsequent exposures, even at very low concentrations. Use respiratory protection if ventilation is inadequate (NIOSH-approved acid gas cartridge respirator for concentrations up to 50 ppm, SCBA for higher concentrations).

Incompatibility - Formaldehyde: A serious safety hazard: hydrochloric acid reacts with formaldehyde (or formaldehyde-containing products) to form bis(chloromethyl) ether (BCME) and chloromethyl methyl ether (CMME), both of which are potent carcinogens (IARC Group 1). NEVER store hydrochloric acid near formaldehyde, formalin, or any formaldehyde-releasing preservatives.

Incompatibility - Oxidizers: Hydrochloric acid reacts with strong oxidizing agents (sodium hypochlorite - bleach, potassium permanganate, potassium dichromate, chlorates, perchlorates, peroxides, etc.) to produce toxic and hazardous chlorine gas (Cl₂). NEVER mix hydrochloric acid with bleach or other oxidizing agents.

Important Disclaimer: This Technical Data Sheet (TDS) is for informational purposes only. For complete safety, handling, storage, and regulatory compliance information, always refer to the official Safety Data Sheet (SDS) provided by the manufacturer/supplier. Hydrochloric acid is a hazardous corrosive material. Always wear appropriate personal protective equipment (PPE). Always add acid to water, never water to acid. Ensure adequate ventilation. Protect from incompatibles. In case of emergency, seek immediate medical attention.