- What it is. This citric acid solution contains 10 g of citric acid per 100 mL of water and comes ready to use in 1 L and 1 gallon sizes. It is made from USP-grade citric acid and is a clear, colorless liquid with a density of about 1.04 g/cm³.
- Chemical identity. Citric acid (2-hydroxypropane-1,2,3-tricarboxylic acid, CAS 77-92-9, C6H8O7, 192.13 g/mol) is a weak organic acid that occurs naturally in citrus fruits. Commercial citric acid is produced mainly by fermentation of sugars with the mold Aspergillus niger.
- A triprotic acid. Each citric acid molecule carries three carboxylic acid groups, which release protons in steps with pKa values of about 3.1, 4.8, and 6.4. That stepwise behavior makes citric acid and its citrate salts useful for buffers across a broad range from roughly pH 3 to 6.2.
- How acidic it is. A 10% solution of citric acid has a pH of about 1.7. It is acidic enough to dissolve mineral scale and metal oxides, yet far milder to handle than mineral acids: in this dilute form it is classified only as an eye irritant.
- A natural chelator. Citrate binds calcium, magnesium, iron, and other metal ions in soluble complexes. That chelating action is why citric acid solutions remove limescale and rust stains, and why citric acid passivates stainless steel by dissolving free iron from the surface without attacking the base metal.
- Building citrate buffers. Combined with sodium citrate or a base such as sodium hydroxide, citric acid forms citrate buffers used in enzyme work and chromatography. Starting with a standardized 10% solution speeds preparation because the acid is already dissolved and its concentration is known.
- Why a ready-made 10% solution. Buying a pre-dissolved solution saves weighing time, avoids citric acid dust, and provides consistent strength from batch to batch. The 1 L size suits routine use and the 1 gallon size suits higher volumes.
- Where it is used. Labs and production areas use 10% citric acid to descale glassware, water baths, and equipment; adjust pH and prepare citrate buffers; perform gentle acid rinses; clean and passivate stainless steel; and in food and teaching labs where a mild, naturally derived acid is preferred.
Technical Specifications
| Chemical Name | Citric acid, aqueous solution |
| Active Ingredient | Citric acid (anhydrous basis) |
| CAS Numbers | 77-92-9 (citric acid); 7732-18-5 (water) |
| EC Number (active) | 201-069-1 |
| Synonyms | 2-Hydroxypropane-1,2,3-tricarboxylic acid, hydroxytricarballylic acid |
| Formula (active) | C6H8O7 (HOC(COOH)(CH2COOH)2) |
| Molecular Weight (active) | 192.13 g/mol |
| Concentration | 10% (w/v), 100 g/L |
| Source Material | Manufactured from USP grade citric acid |
| pKa Values | About 3.1, 4.8, 6.4 |
| pH (10% solution) | About 1.7 |
| Density | About 1.04 g/cm³ |
| Melting / Boiling Point | About 0 °C / 100 °C |
| Appearance | Clear, colorless liquid |
| Molarity (active) | About 0.52 M (calculated from 100 g/L) |
| Physical State | Liquid, aqueous solution |
| Melting Point (active, solid) | About 153 °C |
| Water Solubility (active, solid) | About 1,450 g/L at 20 °C |
| Hazard Classification | Eye Irrit. 2A (H319), signal word Warning |
| NFPA 704 | Health 1, Flammability 0, Instability 0 |
| Storage | Room temperature, tightly closed |
| Package Size | 1 L; 1 gallon |
Available Variants
- CA0010-1: 1 L for routine lab use.
- CA0010-128: 1 gallon for higher volumes.
Applications / Common Uses
- Descaling: Dissolves limescale from glassware, water baths, and equipment.
- Citrate buffer preparation: Supplies the acid component for citrate buffers between about pH 3 and 6.
- pH adjustment: Lowers pH with a mild, naturally derived acid.
- Stainless steel passivation: Removes free iron from stainless surfaces in cleaning and passivation steps.
- Acid rinse: Neutralizes alkaline residues after caustic cleaning.
Storage, Handling & Shipping
Store the solution tightly closed at room temperature, away from strong bases, oxidizers, and reactive metals. Dilute citric acid can support mold growth during long storage, so keep the container closed, avoid contaminating the stock, and discard cloudy solution.
- Incompatible materials: Strong bases, strong oxidizers, and reactive metals such as zinc, aluminum, and galvanized steel.
- Personal protection: Safety glasses or goggles and nitrile gloves.
- Spill response: Absorb or neutralize with sodium bicarbonate, then rinse the area with water.
- First aid: Eyes: rinse with water for several minutes and seek medical advice if irritation persists. Skin: wash with water.
- GHS signal word: Warning. Causes serious eye irritation.
- NFPA 704: Health 1, Flammability 0, Instability 0.
- DOT / shipping: Typically not regulated for transport.
Related Categories & Services
- Shop Organic Acids for related products in this category.
- Explore Acids and ACS Grade Laboratory Chemicals.
- Vendor Managed Inventory (VMI) Program: Lab Pro can stock, track, and replenish this item on site so it never runs out. Contact info@labproinc.com or 888-452-2776 to set up a VMI assessment.
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FAQs
What is the pH of a 10% citric acid solution?
A 10% citric acid solution has a pH of about 1.7. It is strongly acidic for a weak acid because the solution is concentrated, but it is still much milder to handle than mineral acids. In this form it is classified mainly as an eye irritant, so goggles are the key protection.
What is 10% citric acid used for in the lab?
It is used to descale glassware, water baths, and equipment, prepare citrate buffers, adjust pH, rinse away alkaline residues, and support stainless steel cleaning and passivation. Its chelating action binds calcium and iron, which is why it removes mineral deposits and rust stains effectively. It is also a mild acid rinse after caustic cleaning.
How does citric acid passivate stainless steel?
Citric acid dissolves free iron and iron oxides from the stainless steel surface while leaving the chromium-rich base metal intact. The chromium then forms a thin protective oxide layer. Citric acid passivation is valued because it avoids the hazards and waste issues of nitric acid methods.
Is citric acid solution safe to handle?
In this 10% form, citric acid is classified as an eye irritant rather than a corrosive. Wear safety glasses or goggles and gloves, rinse splashes with water, and keep it away from strong bases and reactive metals. Always check the safety data sheet before use.
How should I store citric acid solution?
Keep it tightly closed at room temperature, away from bases and reactive metals. Dilute citric acid can support mold growth if contaminated, so avoid dipping pipettes into the stock, keep the container closed, and discard any solution that becomes cloudy or develops visible growth. Label the date it was opened.
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