Muriatic Acid

The word muriatic comes from the Latin muria, meaning “brine” or “salt.” That name stuck because concentrated salt water has long been a key reagent in the production of this acid.

Muriatic acid is a diluted, slightly impure form of hydrochloric acid (HCl). It typically sits at a pH of about 1 to 2, making it strongly acidic but milder than laboratory-grade HCl. You’ll often notice it has a yellowish tint rather than being colorless, and that color comes from trace impurities like dissolved iron.

Even though muriatic acid is less concentrated than pure hydrochloric acid, don’t let the word “diluted” fool you. It’s still highly corrosive and demands careful handling. You’ll find it sold at hardware stores for concrete cleaning, pool maintenance, and heavy-duty household jobs. Let’s walk through how it’s made, how concentrated it is, what you can do with it, and how to stay safe.

Production of Muriatic Acid

Hydrochloric acid is simply an aqueous solution of hydrogen chloride gas (HCl). To produce muriatic acid commercially, manufacturers burn hydrogen gas and chlorine gas together inside a synthesis chamber. The resulting hydrogen chloride gas is then dissolved in water and diluted to the target concentration.

The direct synthesis reaction looks like this:

H₂(g) + Cl₂(g) → 2HCl(g) → 2HCl(aq)

A second major industrial route is the Mannheim process. Here, sodium chloride (common table salt) reacts with sulfuric acid in a furnace. This method has been used for centuries and remains economically important because it also produces sodium sulfate as a useful byproduct.

2NaCl + H₂SO₄ → 2HCl + Na₂SO₄

There’s also a less common route that uses sodium chloride, sulfur dioxide, water vapor, and atmospheric oxygen. You’ll sometimes see this called the Hargreaves process:

4NaCl + 2SO₂ + 2H₂O + O₂ → 2Na₂SO₄ + 4HCl

In all three methods, the final step is the same: dissolve the HCl gas in water and adjust the concentration downward until you reach what’s sold as muriatic acid.

Concentration

There is no single standard concentration for muriatic acid, so you should always check the product label before using it. Industrial-grade muriatic acid is typically about 31.5% HCl by mass, while consumer-grade formulas sold at hardware stores usually range from about 14.5% to 29%.

With a pH of 1 to 2, muriatic acid has acidity comparable to gastric juice (which is partly composed of HCl) and lemon juice. But pH alone doesn’t tell you the full story about corrosiveness. Lemon juice is only about 5-6% citric acid, a weak organic acid, while muriatic acid at 14-29% is a concentrated strong acid. That’s why muriatic acid can burn bare skin in seconds, while lemon juice just stings a paper cut.

If you’re using muriatic acid for pool maintenance, you’ll typically want the 14.5% or 20% formulation. For heavy-duty concrete etching or rust removal, the stronger 29-31.5% solutions are more effective. Either way, the concentration determines how carefully you need to handle it and how much you should dilute it before application.

Uses of Muriatic Acid

Muriatic acid is one of the most versatile industrial chemicals you’ll encounter. Its uses span heavy industry, food processing, construction, and everyday household cleaning. The common thread is that most applications rely on its ability to dissolve minerals, oxides, and organic residues.

• Leather tanning – Processing raw hides into finished leather
• Gelatin production – Extracting collagen from animal bones
• Pearl processing – Removing the outer layers of pearls to reveal luster
• PVC manufacturing – Commercial synthesis of vinyl chloride and polyvinyl chloride
• Descaling – Removing mineral scale from boilers, pipes, and equipment
• Brick and masonry cleaning – Removing mortar residue during construction
• Drain clearing – Dissolving organic blockages in clogged drains
• Ion exchange resin regeneration – Restoring water softeners and purification systems
• Inorganic chemical synthesis – Manufacturing metal chlorides and other compounds
• Steel pickling – Removing iron oxide (rust) and scale from steel before galvanizing or coating
• Salt purification – Refining common salt (NaCl) to food or pharmaceutical grade
• Oil well acidizing – Dissolving limestone and dolomite rock formations to improve crude oil flow
• pH control – Adjusting the pH of food products, pharmaceuticals, and drinking water
• Swimming pool maintenance – Lowering pool water pH to the ideal 7.2-7.6 range
• Household cleaning – Removing mineral stains from basements, toilets, and concrete surfaces
• Digestion – Your own stomach produces HCl (gastric acid) to break down food and kill bacteria

Safety Precautions

The same corrosive properties that make muriatic acid so useful also make it dangerous. Hydrochloric acid can cause severe chemical burns on contact with skin and serious, potentially permanent eye damage if splashed in your eyes. If swallowed, it corrodes the lining of the mouth, throat, esophagus, and stomach. Even though muriatic acid is a less concentrated form, it’s absolutely capable of causing all these injuries.

Beyond liquid contact, you also need to worry about the fumes. Muriatic acid releases hydrogen chloride gas, especially in warm conditions or when poured. Inhaling these fumes irritates the respiratory tract and can cause coughing, choking, and lung damage with prolonged exposure. Always work in a well-ventilated area or outdoors.

Always Add Acid to Water for Dilution

If you need to dilute muriatic acid, always pour the acid into water, never the reverse. When you add water to concentrated acid, the heat generated by the exothermic reaction can be intense enough to cause the mixture to boil and splash violently. Chemistry students remember this rule with the mnemonic “do as you oughta, add acid to water.” Follow it every time.

Never Mix with Other Chemicals

Muriatic acid works perfectly well on its own as a cleaner. You should never mix it with bleach (sodium hypochlorite), potassium permanganate, or any other oxidizer. Mixing muriatic acid with bleach produces chlorine gas, which is extremely toxic and can be fatal even in small concentrations. This is one of the most common and dangerous household chemical accidents.

Wear Protective Equipment

Whenever you handle muriatic acid, wear chemical-resistant gloves (neoprene or PVC, not latex), safety goggles or a face shield, long sleeves, and full-length pants. A respirator rated for acid gases is recommended if you’re working in an enclosed space. If any acid splashes on your skin, flush the area immediately with large amounts of running water for at least 15-20 minutes.

Proper Storage and Disposal

Store muriatic acid in its original, tightly sealed plastic container in a cool, dry, well-ventilated area away from metals and incompatible chemicals. To dispose of it, first neutralize the acid by slowly adding baking soda (sodium bicarbonate) until the fizzing stops, then dilute the resulting solution heavily with water (at least a 1:50 ratio). Never pour unneutralized acid down a drain because it corrodes plumbing and harms the environment. For larger quantities, your safest option is to take the acid to a hazardous waste disposal facility.

Muriatic Acid vs. Hydrochloric Acid

You’ll sometimes see the terms muriatic acid and hydrochloric acid used interchangeably, but there is a practical difference. Laboratory-grade or reagent-grade hydrochloric acid is typically 36-38% HCl by mass and is produced to strict purity standards. Muriatic acid, on the other hand, is an industrial or commercial-grade product that’s less concentrated (usually 14.5-31.5%) and may contain impurities like dissolved iron, organic matter, or sulfate residues.

For scientific experiments, titrations, or pharmaceutical manufacturing, you need the purity of reagent-grade HCl. For cleaning your pool, etching concrete, or removing rust from tools, muriatic acid does the job at a fraction of the cost. Chemically, both contain the same active compound. The difference is concentration and purity.

Frequently Asked Questions