Muriatic Acid (Hydrochloric Acid)
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Muriatic acid is the historical and common commercial name for hydrochloric acid (chemical formula HCl), especially the technical/industrial grade sold for cleaning, etching, and pH adjustment.
Properties
- Chemical formula: HCl
- Appearance: Colorless to slightly yellowish liquid (concentrated solutions may fume)
- Odor: Strong, pungent, irritating
- Density: ≈ 1.18 g/cm³ (37% concentration at 20 °C)
- Solubility: Fully miscible with water
- Boiling point: Depends on concentration; azeotrope at ~20% boils at 108.6 °C
- Very strong mineral acid — pH of 37% solution is approximately −1.0
Common Concentrations
| Concentration | Trade name | Typical use |
|---|---|---|
| 31–33% | Muriatic acid (standard) | Pool pH lowering, masonry cleaning |
| 37–38% | Hydrochloric acid (technical) | Industrial, laboratory, pickling |
| 10–20% | Diluted muriatic acid | Household cleaners (sometimes labeled) |
Principal Uses
- Lowering pH in swimming pools and spas
- Concrete etching and cleaning (efflorescence removal)
- Rust and mineral scale removal from masonry, toilets, boilers
- Metal pickling and galvanizing pre-treatment
- pH adjustment in water treatment and chemical manufacturing
- Laboratory reagent (when higher purity)
DANGER — Muriatic acid is extremely corrosive.
It causes severe burns on contact with skin or eyes.
Releases highly irritating HCl vapors/fumes when exposed to air.
Always add acid to water — never water to acid.
Use full face shield, chemical-resistant gloves, apron, and excellent ventilation.
Safety and Handling
- Store in original acid-resistant container (HDPE, rubber-lined, glass)
- Keep away from bases, oxidizers, metals, cyanides, and bleach
- Neutralize spills with sodium bicarbonate or lime (large amounts require professional response)
- First aid: Flush skin/eyes with large amounts of water for at least 15 minutes; seek immediate medical attention
Historical Note
The name "muriatic" comes from Latin muria (brine), as hydrochloric acid was historically produced from common salt (NaCl) and sulfuric acid.