Product Overview
Magnesium Hydroxide ACS (Mg(OH)₂), CAS 1309-42-8, is an inorganic base supplied as an odorless solid powder. Its alkaline character and low solubility in water make it a controlled-release pH adjuster — it raises pH gradually rather than spiking it, which matters in wastewater treatment, neutralization chemistry, and any process where pH control must be steady and predictable.
This material is offered in ACS Grade, the designation that analytical and process-quality buyers specify when their procedures call for a defined purity tier. Available in sizes from 2 lb bench quantities through 55 lb production packs, Magnesium Hydroxide ACS serves water-treatment operators, chemical process engineers, formulators, and research labs that need a reliable, well-documented source of this base.
Why This Grade
ACS Grade is the line item buyers write into purchase specs when their process demands a recognized purity designation — not a technical-grade commodity. Choosing ACS Grade tells your procurement team and your quality department that the material was sourced to that standard tier, which simplifies incoming-material review and keeps your documentation chain clean.
For pH adjustment in wastewater streams, a powder with controlled purity means fewer unknowns in your effluent chemistry. For synthesis work, it reduces the risk of trace contaminants interfering with yields or side reactions. If your process runs on a technical-grade magnesium hydroxide today and you are troubleshooting inconsistent results, specifying ACS Grade is the first variable to tighten.
That said, ACS Grade is not always necessary. If you are using magnesium hydroxide as a bulk neutralizing agent in high-volume industrial waste streams where trace impurity levels are not a concern, a technical grade may be more cost-effective. Match the grade to the sensitivity of your process.
Chemical Profile
Magnesium Hydroxide ACS is an odorless solid powder with a density of 2.36 g/mL. It is practically insoluble in both water and ethanol — a property that defines its behavior in suspension-based applications and its gradual pH-buffering action. The molecular formula is H₂MgO₂ with a molecular weight of 58.320 g/mol. CAS Number: 1309-42-8. These physical characteristics make it straightforward to handle as a dry powder: it does not off-gas, does not generate significant vapor pressure at ambient conditions, and stores stably when kept dry.
Industrial Applications
Magnesium Hydroxide serves as a workhorse base across several industries. Its low solubility is not a limitation — it is the feature. Because it dissolves slowly, it releases hydroxide ions gradually, preventing the pH overshoots that can occur with more soluble bases like sodium hydroxide.
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pH Control in Wastewater Treatment — Operators add magnesium hydroxide powder to acidic waste streams to raise pH toward discharge limits. Its slow-dissolving nature provides a buffering effect that holds pH steady, reducing the need for constant re-dosing. It generates no exothermic spike on contact with water, which simplifies dosing equipment and operator safety compared to caustic soda.
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Neutralizing Agent in Chemical Processes — In chemical manufacturing, magnesium hydroxide neutralizes acid byproducts and adjusts reaction pH without introducing aggressive cations. Its mild alkalinity makes it suitable for processes where a gentler base is required to avoid degrading sensitive intermediates.
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Flame Retardant Additive — When compounded into plastics, rubber, or textile coatings, magnesium hydroxide acts as a flame retardant. It releases water vapor upon thermal decomposition, which dilutes flammable gases and absorbs heat. Unlike halogenated flame retardants, it does not produce toxic or corrosive combustion byproducts.
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Synthesis Intermediate — Magnesium hydroxide serves as a starting material or reagent in the synthesis of other magnesium compounds, including magnesium oxide and various magnesium salts. ACS Grade material is specified for synthesis routes where purity of the starting base directly affects the quality of the end product.
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Pharmaceutical Formulation Ingredient — Magnesium hydroxide is a recognized ingredient in antacid and laxative formulations. Buyers sourcing for pharmaceutical applications should verify independently that the material meets their specific formulation and regulatory requirements.
Handling & Storage
Magnesium hydroxide is not classified as hazardous under GHS based on available data. No signal word, pictograms, or hazard statements apply under the current GHS classification. That said, standard powder-handling practices apply.
PPE: Wear dust-rated gloves and safety glasses. In operations that generate airborne dust — scooping, transferring, or blending — use a NIOSH-approved dust mask or respirator and work under local exhaust ventilation. Prolonged inhalation of any mineral dust is an avoidable exposure.
Storage: Keep containers sealed in a cool, dry area. Magnesium hydroxide is hygroscopic enough that prolonged moisture exposure will cause caking and clumping, degrading the free-flowing character of the powder. HDPE or glass containers are preferred to prevent contamination. Store away from strong acids — contact with concentrated mineral acids produces an exothermic neutralization reaction.
Incompatibilities: Strong acids (hydrochloric, sulfuric, nitric). The reaction is not violent at ambient scale, but combining bulk quantities without controlled addition can generate significant heat and spattering.
Hazmat & Shipping
Magnesium Hydroxide ACS is not assigned a UN number, hazard class, packing group, or regulated proper shipping name (per 49 CFR 172.101). Based on its DOT classification, this material is not regulated as a hazardous material for transport. Shipments do not require hazmat placarding, hazmat shipping papers, or hazmat-certified packaging under DOT regulations.
Shipping guidance reviewed by Andre Taki, DOT Hazmat Specialist.
Documentation
A Safety Data Sheet (SDS) ships with every order, available in English, Spanish, French, and Japanese. A lot-specific Certificate of Analysis (COA) is also available, documenting the analytical results for the specific lot you receive. A Technical Data Sheet (TDS) is on file for buyers who need detailed product specifications beyond the SDS. Request any of these documents at the time of order or contact us directly.
Why Buy from Alliance Chemical
Magnesium Hydroxide ACS is available to order in ten variants across three weight classes — 2 lb, 5 lb, and 55 lb — so you can match your purchase to bench-scale trials or ongoing production without overbuying. Every lot ships with an SDS and a lot-specific COA, and the material's non-hazmat DOT classification means straightforward freight from our Taylor, TX warehouse.
Alliance Chemical has served over 55,000 customers since 1998. Our shipping and handling guidance is reviewed by Andre Taki, DOT Hazmat Specialist (USDOT Registration #2188383), so the documentation and classification data on this page reflect current regulatory standards — not boilerplate.
