Methanesulfonic Acid 70% (MSA)

Methanesulfonic Acid 70% (MSA)
Other Names: MSA, Methanesulphonic acid, MeSO₃H, Methylsulfonic acid

CAS Number: 75-75-2
Sum Formula: CH₄O₃S
Molar Mass: 96.10 g/mol
Appearance: Colorless to slightly yellow clear liquid

Methanesulfonic acid (MSA) is a strong, non-oxidizing organic acid commonly supplied as a 70% aqueous solution. It is highly soluble in water and organic solvents and is widely used in electroplating, chemical synthesis, and acid-catalyzed reactions. It is known for its high thermal and chemical stability and minimal environmental impact compared to mineral acids.

Chemical and Physical Properties

• Density: ~1.35 g/cm³ (70% solution at 20°C)

• Melting Point (pure): 20°C

• Boiling Point: ~167°C (pure compound)

• pKa: ~–1.9 (strong acid)

• Solubility in Water: Fully miscible

• Solubility in Other Solvents: Miscible with alcohols, ethers, and polar organics

• Odor: Mild or faintly sour

Applications

• Catalysis: Acid catalyst in esterification, alkylation, and dehydration reactions

• Electroplating: Used as a conductive, stable acid in metal finishing baths

• Chemical Synthesis: Employed as a reagent or acid medium in specialty chemical production

• Cleaning Formulations: Found in descaling and metal surface treatment chemicals (industrial-grade)

Safety

Signal Word: Danger

• Eye Contact: Rinse thoroughly with water for at least 15 minutes. Seek immediate medical attention

• Skin Contact: Remove contaminated clothing and rinse affected skin with water. Seek medical advice

• Inhalation: Move to fresh air. Provide oxygen if breathing is difficult. Seek medical attention

• Ingestion: Do not induce vomiting. Rinse mouth and seek immediate medical help

Handling and Storage

• Storage Conditions: Store in tightly closed containers in a cool, dry, well-ventilated area. Keep away from bases, strong oxidizers, and moisture

• Handling Precautions: Handle with appropriate PPE under local exhaust ventilation. Avoid skin and eye contact, and exposure to vapors