Material Safety Data Sheet: Magnesium Hydroxide
Identification
Product Name: Magnesium Hydroxide
CAS Number: 1309-42-8
Chemical Formula: Mg(OH)2
Synonyms: Milk of Magnesia, Magnesia Hydrate, Magnesium Dihydroxide
Manufacturer: Refer to supplier information for direct contact details
Recommended Use: Flame retardant, pharmaceutical antacid, wastewater treatment additive
Emergency Phone: Local poison control center or fire department number
Hazard Identification
Main Hazards: Dust may cause irritation to respiratory tract, eyes, and skin. Inhalation can aggravate pre-existing respiratory issues. Ingestion of large amounts can lead to gastrointestinal symptoms including diarrhea. Not classified as flammable or explosive.
Hazard Statements: May cause slight eye and skin irritation. Can cause transient gastrointestinal discomfort if swallowed.
Pictograms: Non-hazardous under most regulatory guidelines
Signal Word: None required under GHS
Precautionary Statements: Avoid generating dust. Use adequate ventilation. Wear appropriate personal protective equipment.
Composition / Information on Ingredients
Substance: Magnesium Hydroxide
Concentration: >95% by weight
Impurities: May include trace amounts of magnesium carbonate or calcium compounds depending on source.
Other Information: No hazardous impurities present at concentrations that require disclosure under applicable regulations.
First Aid Measures
Inhalation: Move to fresh air. Seek medical attention if symptoms persist. Rinse mouth and nose with water if dust inhaled.
Skin Contact: Rinse thoroughly with water. Remove contaminated clothing and launder before reuse. Apply moisturizer to relieve minor irritation.
Eye Contact: Flush eyes with plenty of water for several minutes, lifting upper and lower eyelids occasionally. Remove contact lenses if present.
Ingestion: Rinse mouth with water. Do not induce vomiting. Give water to drink if victim is conscious.
Medical Attention: Persistent symptoms should prompt consultation with a physician or poison center.
Fire-Fighting Measures
Flammability: Not flammable. Does not support combustion.
Extinguishing Media: Use media appropriate for surrounding fire. Water, foam, dry chemical, or carbon dioxide all suitable.
Special Hazards: Product may decompose at high temperatures above 350°C, releasing water and forming magnesium oxide. No unusual fire or explosion hazards expected.
Protective Equipment for Firefighters: Standard protective equipment and self-contained breathing apparatus.
Accidental Release Measures
Personal Precautions: Prevent dust formation. Ventilate area. Use personal protective gear including goggles, gloves, and dust mask.
Environmental Precautions: Do not let large amounts enter surface water or drainage systems. Small quantities can be neutralized and cleaned with water.
Cleanup Methods: Sweep up and collect in suitable containers for reuse or disposal. Vacuum preferred to limit airborne dust. Rinse affected area with water once bulk material is removed.
Reporting: For large spills, notify appropriate local and national authorities.
Handling and Storage
Handling: Keep containers tightly closed. Minimize dust generation. Avoid breathing dust and contact with skin and eyes. Wash hands thoroughly after handling.
Storage: Store in cool, dry, well-ventilated area away from incompatible materials such as acids. Keep away from moisture to prevent lump formation. Label containers clearly.
Incompatibilities: Avoid storage near strong acids. Reacts with acids to release heat and form magnesium salts.
Specific Requirements: Use containers and equipment that prevent moisture ingress.
Exposure Controls and Personal Protection
Exposure Limits: ACGIH TLV: 10 mg/m3 (total dust). OSHA PEL: 15 mg/m3 (total dust), 5 mg/m3 (respirable fraction).
Engineering Controls: Maintain adequate ventilation in work areas. Use process enclosures or local exhaust if dust generation increases.
Personal Protective Equipment: Safety goggles or glasses, dust-resistant gloves, NIOSH-approved dust mask or respirator in areas with dust. Protective clothing recommended for prolonged exposure.
Hygiene Measures: Wash hands and any exposed skin after handling. Avoid eating, drinking, or smoking in work area.
Environmental Controls: Prevent the release of dust into the environment by using proper containment or dust suppression.
Physical and Chemical Properties
Appearance: White powder or crystalline solid
Odor: Odorless
Odor Threshold: Not applicable
pH: 9.5–10.5 (10% suspension in water)
Melting Point: Decomposes above 350°C
Boiling Point: Not applicable (decomposes)
Flash Point: Not applicable
Evaporation Rate: Not applicable
Flammability: Non-flammable
Relative Density: 2.36–2.40 g/cm3
Solubility: Practically insoluble in water (0.009 g/100 mL at 20°C), more in acidic conditions
Vapor Pressure: Not applicable
Partition Coefficient: Not determined
Auto-ignition Temperature: Not applicable
Decomposition Temperature: >350°C (yields MgO and water)
Viscosity: Not applicable
Stability and Reactivity
Stability: Chemically stable at recommended storage and handling conditions.
Conditions to Avoid: Contact with strong acids, high humidity, and temperatures above 350°C.
Materials to Avoid: Strong acids, ammonium salts.
Decomposition Products: Magnesium oxide, water vapor.
Hazardous Reactions: Contact with acids leads to heat and magnesium salt formation.
Polymerization: Will not occur.
Toxicological Information
Routes of Exposure: Inhalation, ingestion, skin and eye contact.
Acute Toxicity: Non-toxic at typical occupational exposure levels. LD50 (oral, rat): >8,500 mg/kg. High amounts can cause mild gastrointestinal irritation.
Skin: May cause slight, reversible irritation.
Eyes: May cause mechanical irritation.
Inhalation: Prolonged exposure to large amounts of dust may cause coughing or respiratory discomfort.
Chronic Effects: No evidence for chronic toxicity or carcinogenicity in available animal or epidemiological studies. Prolonged ingestion of high doses may affect electrolyte balance.
Sensitization: Not a known sensitizer.
Ecological Information
Environmental Fate: Naturally occurring mineral. Practically insoluble in water. In soil, transforms to magnesite and other stable mineral forms over time.
Ecotoxicity: Not harmful to aquatic organisms at expected environmental concentrations. Can increase pH of bodies of water if released in quantity.
Bioaccumulation: Not expected to bioaccumulate.
Mobility in Soil: Low mobility due to insolubility. Remains near release site in particulate form.
Degradability: Inorganic material; does not undergo biodegradation.
Further Information: Dispersal of large amounts in surface water may temporarily elevate local pH.
Disposal Considerations
Waste Disposal Methods: Dispose as non-hazardous waste according to local, regional, and national regulations. Reuse or recycle where possible. Small amounts can be flushed to drain with water if permitted.
Contaminated Packaging: Rinse thoroughly before recycling or disposal. Follow regulations for non-hazardous solid waste.
Special Considerations: Avoid large releases to the environment. Secure loose powder in sealed containers before disposal.
Transport Information
UN Number: Not regulated
UN Proper Shipping Name: Magnesium Hydroxide
Transport Hazard Class: Not classified
Packing Group: Not assigned
Marine Pollutant: No
Notes: Not subject to transport regulations for hazardous materials under ADR, IATA, or IMDG codes.
Regulatory Information
TSCA Status: Listed on US Toxic Substances Control Act inventory
REACH Status: Registered under REACH (EU)
OSHA Hazard Communications: Not classified as hazardous
WHMIS (Canada): Not controlled
SARA Title III: Not listed as a reportable substance
California Prop 65: Not listed
Other Regulations: Subject to workplace hazard communication and handling guidelines in most industrial jurisdictions. Product safety information should always accompany shipment and use.
