What Does Magnesium Hydroxide Do? Key Uses, Benefits & Applications

Discover what magnesium hydroxide does in medicine, industry, and daily products. Simple explanations, real examples, and expert insights for quick understanding.

What does magnesium hydroxide do?
If you’ve seen it in antacids, wastewater treatment systems, flame-retardant materials, or chemical listings and wondered what its actual job is, you’re asking the right question.

Struggling to understand where Mg(OH)₂ fits in?
Let me explain it like I would to a colleague in the lab.

What Does Magnesium Hydroxide Do? (Short Answer)

Magnesium hydroxide (Mg(OH)₂) acts as a:

Antacid (neutralizes stomach acid)

Laxative (draws water into the intestines)

pH stabilizer in water and wastewater treatment

Flame retardant for plastics and construction materials

Filler and stabilizer in industrial formulations

It’s versatile, safe when used properly, and extremely cost-effective.

Major Functions of Magnesium Hydroxide

1. It Neutralizes Stomach Acid (Antacid Use)

This is the use most people know.

Magnesium hydroxide reacts with stomach acid to create water and magnesium salts.

Why it works:

Fast relief

Gentle on the stomach

Doesn’t cause rebound acid like strong chemical antacids

You’ll see it in OTC products like “milk of magnesia.”

2. It Works as a Laxative

Mg(OH)₂ helps relieve occasional constipation.

It pulls water into the intestines, which softens stool and stimulates movement.

Why people prefer it:

Mild action

Works predictably

Not habit-forming

3. It Controls pH in Water Treatment

Industrial users rely on magnesium hydroxide to treat acidic water streams.

What it does in water treatment:

Neutralizes acidity

Reduces heavy metal solubility

Produces less sludge than lime

Maintains stable pH over time

Wastewater engineers love its buffering ability.

4. It Works as a Flame Retardant

Magnesium hydroxide decomposes when heated and releases water vapor.

That reaction slows burning and limits smoke formation.

It’s used in:

Cables and wires

Rubber products

Building materials

Plastics

A great alternative to halogen-based fire retardants.

5. It Acts as a Filler and Additive in Manufacturing

Magnesium hydroxide is used in:

Plastics

Rubber compounds

Coatings

Ceramics

Adhesives

What it does:

Improves heat resistance

Enhances mechanical strength

Helps stabilize materials during processing

Simple material with a big impact.

Why Magnesium Hydroxide Is So Useful

High Safety Profile

Non-toxic, widely approved in foods, pharma, and water treatment.

Strong pH Buffering

Better stability than lime, caustic soda, or quick-reacting alkalis.

Cost-Effective

Low cost for mass industrial use.

Thermal Decomposition Benefits

Ideal for eco-friendly flame retardant applications.

Real-Life Example

A colleague in a wastewater plant once told me:
“We switched from caustic soda to magnesium hydroxide, and our pH swings disappeared overnight.”

Why?
Because magnesium hydroxide releases alkalinity slowly and evenly.
Less risk. More stability. Fewer headaches for operators.

That’s the kind of behind-the-scenes value Mg(OH)₂ delivers every day.

FAQs: What Does Magnesium Hydroxide Do?

1. Is magnesium hydroxide safe to take?

Yes—when used correctly.
It’s widely used as an antacid and mild laxative.

2. Does magnesium hydroxide dissolve in water?

Very little.
It’s only slightly soluble, which is why it forms a suspension like “milk of magnesia.”

3. Why is magnesium hydroxide used in fire-resistant materials?

Because it releases water when heated, lowering temperature and slowing fire spread.

4. What does magnesium hydroxide do in wastewater?

It raises pH, removes heavy metals, and stabilizes acidic streams.

5. What is the difference between magnesium hydroxide and magnesium oxide?

Mg(OH)₂ neutralizes slowly and gently.
MgO reacts faster and is more alkaline.

Final Thoughts

So, what does magnesium hydroxide do?
A lot more than people realize.

It supports human health.
Protects materials from fire.
Stabilizes wastewater.
And strengthens countless industrial products.

Simple compound, big impact.

Now you have a clear, expert-level picture of what does magnesium hydroxide do and why industries rely on it.