Oxalic Acid Aqueous Solution (2%): Lab Use & Safety Guide

Oxalic Acid Aqueous Solution (2%) is a ready-to-use, precisely formulated dicarboxylic acid reagent designed for a range of laboratory applications including metal ion precipitation, biological staining, analytical chemistry, and surface treatment procedures.

Product Name

Oxalic Acid Aqueous Solution (2%)

SKU

O1529589

Concentration

2% (w/v) in water

Chemical Formula

C₂H₂O₄ (MW 90.03 g/mol)

Physical Form

Clear, colorless aqueous solution

Storage Condition

Store at room temperature (15–25 °C), tightly sealed, away from bases and oxidizers

pH (2% solution)

Approximately 1.3–1.7 (strongly acidic)

Overview and Chemical Properties

Oxalic acid (ethanedioic acid, CAS 144-62-7) is the simplest dicarboxylic acid. Its molecular formula is C₂H₂O₄ with a molecular weight of 90.03 g/mol. In aqueous solution, oxalic acid behaves as a moderately strong diprotic acid (pKa₁ ≈ 1.25, pKa₂ ≈ 4.27), making a 2% aqueous solution strongly acidic with a pH typically in the range of 1.3–1.7.

The 2% aqueous solution supplied as SKU O1529589 is a ready-to-use, clear, colorless liquid. Oxalic acid is notable for its ability to form stable, insoluble complexes (oxalates) with many divalent metal cations such as Ca²⁺, Fe²⁺, and Mn²⁺, a property that underpins many of its laboratory applications.

Oxalic acid also acts as a mild reducing agent and can reduce permanganate and other oxidizing agents, a reaction exploited in titrimetric analysis.

Laboratory Applications and Protocols

Analytical Chemistry – Standardization: A 2% oxalic acid solution can serve as a primary standard solution for standardizing potassium permanganate (KMnO₄) titrant. Pipette an accurate volume into a conical flask, acidify with dilute H₂SO₄, warm to 60–80 °C, and titrate slowly with KMnO₄ until a faint pink endpoint persists for at least 30 seconds.

Histology and Biological Staining: Oxalic acid solutions are used in Weigert's iron hematoxylin protocols and as a bleaching/differentiation agent in Mallory's trichrome and certain silver staining procedures. Immerse tissue sections for 1–5 minutes, then rinse thoroughly with distilled water before proceeding to the next staining step.

Metal Removal and Surface Treatment: A 2% oxalic acid solution is effective for removing iron rust stains from laboratory glassware, ceramics, and certain textile substrates. Apply directly to the stained surface, allow 5–15 minutes of contact time, then rinse with copious water.

Calcium Oxalate Precipitation: In mineral analysis or biochemical assays, the 2% solution can be used to precipitate calcium as calcium oxalate (CaC₂O₄) for gravimetric determination of calcium content.

Dilution Note: If a lower concentration is required, dilute with deionized water using volumetric glassware. Always add the acid solution to water, not water to acid, to control exothermic effects.

Safety, Handling, and First Aid

Hazard Classification: Oxalic acid is harmful if swallowed, inhaled, or absorbed through skin. It is classified as harmful (Xn) under traditional EU classification and may bear GHS07 warning pictograms. Although the 2% solution is dilute, appropriate precautions must still be observed.

Personal Protective Equipment (PPE): Always wear chemical-resistant gloves (nitrile or neoprene), safety goggles or face shield, and a laboratory coat when handling this solution. Work in a well-ventilated area or fume hood if handling large volumes.

Skin and Eye Contact: In case of skin contact, remove contaminated clothing and wash the affected area immediately with soap and large amounts of water for at least 15 minutes. For eye contact, irrigate immediately with copious amounts of water for at least 15 minutes and seek prompt medical attention.

Ingestion: Do NOT induce vomiting. Rinse mouth with water and seek immediate medical attention. Oxalic acid can chelate serum calcium and cause hypocalcemia if ingested in significant quantities.

Inhalation: Move affected person to fresh air. Seek medical attention if irritation or respiratory distress persists.

Incompatibilities: Keep away from strong bases (NaOH, KOH), strong oxidizing agents (permanganates, chromates), and reactive metals. Neutralization with bases generates heat.

Storage, Stability, and Disposal

Storage: Store the 2% oxalic acid aqueous solution at room temperature (15–25 °C) in a tightly closed original container. Keep away from direct sunlight, heat sources, strong bases, and oxidizing agents. Store in a dedicated acid cabinet if institutional regulations require it.

Stability: Aqueous oxalic acid solutions are generally stable under recommended storage conditions. However, concentrated solutions may deposit oxalic acid dihydrate crystals upon cooling; gentle warming and mixing will re-dissolve the crystals. Avoid prolonged exposure to air to minimize contamination.

Shelf Life: When stored as directed, the solution should maintain stated concentration for an extended period; consult the product label or certificate of analysis (CoA) for the specific expiry date.

Disposal: Dispose of oxalic acid solutions in accordance with local, regional, and national regulations. Do not pour down the drain in large quantities without neutralization. Neutralize dilute solutions with sodium bicarbonate or dilute sodium hydroxide to pH 6–8, then flush with large volumes of water if permitted by local regulations. For larger quantities, use a licensed chemical waste disposal contractor. Always consult the current Safety Data Sheet (SDS) before disposal.

Quality and Ordering Information

Product SKU: O1529589

Product Name: Oxalic Acid Aqueous Solution (2%)

Supplier: Aladdin Scientific

Quality Assurance: Each lot of Oxalic Acid Aqueous Solution (2%) is manufactured under quality-controlled conditions. A Certificate of Analysis (CoA) is available for each batch and can be requested from Aladdin Scientific's customer service or downloaded from the product page. The CoA documents concentration verification, appearance, and any additional quality parameters tested.

Ordering: To order, visit the Aladdin Scientific website and search by SKU O1529589, or contact your regional Aladdin Scientific sales representative. Bulk quantities and custom concentrations may be available upon request.

Technical Support: For application-specific questions, protocol assistance, or safety information, contact Aladdin Scientific's technical support team via the website or by phone.

Frequently asked questions

What is the recommended storage temperature for Oxalic Acid Aqueous Solution (2%)?

The solution should be stored at room temperature, typically 15–25 °C, in a tightly sealed container away from direct sunlight, strong bases, and oxidizing agents. Avoid freezing, as this may cause precipitation of oxalic acid dihydrate crystals.

Can the 2% Oxalic Acid Aqueous Solution be used directly for KMnO₄ standardization?

Yes, a 2% oxalic acid solution can be used as a primary standard for standardizing KMnO₄ titrant. Acidify the solution with dilute sulfuric acid, warm to approximately 60–80 °C, and titrate with the KMnO₄ solution until a persistent faint pink endpoint is reached. Accurate volumetric measurement is essential for reliable standardization results.

What personal protective equipment is required when handling this solution?

At minimum, wear chemical-resistant gloves (nitrile or neoprene), safety goggles or a face shield, and a laboratory coat. When handling large volumes, work in a well-ventilated area or fume hood to minimize inhalation risk. Always consult the current Safety Data Sheet (SDS) for complete hazard and PPE information.

How should accidental skin or eye contact with the solution be treated?

For skin contact, remove contaminated clothing and rinse the affected area thoroughly with soap and water for at least 15 minutes. For eye contact, immediately irrigate with copious water for at least 15 minutes and seek medical attention promptly. Do not rub the eyes during rinsing.

Is the 2% Oxalic Acid Aqueous Solution suitable for histological staining applications?

Yes, oxalic acid solutions including the 2% formulation are used in several histological protocols such as Weigert's iron hematoxylin and as a differentiation or bleaching agent in trichrome and silver staining methods. Immersion times typically range from 1 to 5 minutes depending on the specific protocol, followed by thorough rinsing with distilled water.

References

1. Clayden, J.; Greeves, N.; Warren, S. Organic Chemistry, 2nd ed.; Oxford University Press: Oxford, 2012. (General reference for dicarboxylic acid properties.)
2. Skoog, D.A.; West, D.M.; Holler, F.J.; Crouch, S.R. Fundamentals of Analytical Chemistry, 9th ed.; Cengage Learning: Mason, OH, 2013. (Permanganate standardization with oxalic acid.)
3. Bancroft, J.D.; Gamble, M. (Eds.) Theory and Practice of Histological Techniques, 6th ed.; Churchill Livingstone: Edinburgh, 2008. (Histological staining applications of oxalic acid.)
4. Sigma-Aldrich / Merck. Safety Data Sheet: Oxalic Acid. (Reference for GHS classification, PPE, and disposal guidance for oxalic acid.)

Products are supplied for research and development use only. Not for use in humans, animals, diagnosis, or therapy.