Oxalic acid anhydrous is a highly useful compound that finds application across multiple industries, including pharmaceuticals, metallurgy, cleaning agents, and even wood restoration. With the CAS number144-62-7, it is recognized and classified as a pure, water-free form of oxalic acid. This solid, crystalline substance is known for its acidic and reducing properties, and it plays a significant role in both industrial and laboratory settings. Understanding its composition, properties, safety aspects, and uses helps in recognizing its value in various chemical and manufacturing processes.
Chemical Identity and Structure
Oxalic acid anhydrous (CAS No. 144-62-7) is an organic compound with the formula C2H2O4. As the anhydrous version, it lacks water molecules, making it distinct from oxalic acid dihydrate. The molecular weight of this compound is approximately 90.03 g/mol.
The compound consists of two carboxylic acid groups (-COOH) bonded together, making it one of the simplest dicarboxylic acids. Its strong acidity and chelating abilities stem from this structure. In its anhydrous form, oxalic acid appears as a white crystalline solid, which can easily absorb moisture from the air.
Key Physical Properties
- CAS Number: 144-62-7
- Molecular Formula: C2H2O4
- Molecular Weight: 90.03 g/mol
- Appearance: White to off-white crystalline solid
- Solubility: Soluble in water, ethanol, and ether
- Melting Point: 189-191°C (sublimes)
Due to its tendency to absorb water, oxalic acid anhydrous must be stored in tightly sealed containers to prevent rehydration into its dihydrate form.
Production and Purification
Oxalic acid anhydrous is typically produced through the oxidation of carbohydrates or glucose using nitric acid, or through the reaction of sodium formate in the presence of a catalyst. Once formed, it can be dehydrated through careful heating or vacuum drying to remove the water content, leaving behind the anhydrous version.
Industrial production is focused on maintaining high purity levels, especially for pharmaceutical or laboratory-grade applications. The final product is often refined through recrystallization processes to remove impurities and ensure chemical stability.
Industrial Applications of Oxalic Acid Anhydrous
The versatility of oxalic acid anhydrous lies in its strong acidic and reducing nature. It has a wide range of applications, including:
1. Metal Cleaning and Surface Preparation
Oxalic acid is a preferred chemical in metal cleaning and rust removal. It binds to metal ions, forming soluble complexes, which allows for effective descaling and surface treatment. It is used on stainless steel, brass, and aluminum to remove tarnish, corrosion, and oxide layers without damaging the underlying surface.
2. Textile and Leather Industry
In textile processing, oxalic acid is used as a bleaching agent and dyeing assistant. Its reducing ability helps in the removal of excess dye and residual chemicals. In the leather industry, it helps soften hides and eliminate unwanted stains.
3. Pharmaceutical and Laboratory Use
Oxalic acid anhydrous is employed in pharmaceutical manufacturing as an intermediate in the synthesis of certain active ingredients. In laboratories, it is used as a standard reagent for titration and also plays a role in analytical chemistry for calcium and rare earth metal analysis.
4. Wood Bleaching and Restoration
Woodworkers and restoration specialists use oxalic acid to lighten wood and remove dark stains caused by water damage or rust. It is effective at bringing out natural grain patterns and rejuvenating old or discolored surfaces.
5. Agriculture and Beekeeping
Though not as common, oxalic acid has niche uses in agriculture as a fungicide and in beekeeping to control varroa mites. In such applications, the dosage and exposure must be carefully controlled to avoid toxicity.
Handling and Safety Considerations
Oxalic acid anhydrous, while useful, must be handled with caution due to its toxic and corrosive nature. Safety data sheets classify it as harmful if swallowed or inhaled, and it can cause skin and eye irritation.
Safety Guidelines
- Always use protective gloves and eye protection when handling.
- Avoid inhaling dust or fumes; work in a well-ventilated area or fume hood.
- In case of contact with skin or eyes, rinse immediately with plenty of water and seek medical advice.
- Store in a cool, dry place away from moisture and incompatible materials like oxidizers or strong bases.
Oxalic acid is also toxic to humans in high doses and may affect the kidneys if ingested. It binds to calcium in the body, potentially forming insoluble calcium oxalate crystals, which can cause health issues such as kidney stones.
Environmental Impact and Disposal
Though oxalic acid anhydrous is biodegradable, it should not be released directly into the environment in large quantities. Disposal should comply with local regulations, and small lab-scale amounts can usually be neutralized with sodium bicarbonate before disposal.
Industrially, wastewater containing oxalic acid must be treated to reduce acidity and neutralize the chemical to prevent harm to aquatic systems and soil.
Regulatory and Quality Standards
Due to its potential hazards, oxalic acid anhydrous is subject to various safety and transport regulations. It is listed as a hazardous substance under international chemical safety frameworks. When used in pharmaceuticals or food-related processes, it must meet stringent purity and contamination limits as set by regulatory bodies such as ISO, REACH, and FDA (if applicable).
Manufacturers often provide certificates of analysis (COAs) with each batch to confirm compliance with these standards. Quality assurance plays a vital role in applications where oxalic acid is used as a reagent or intermediate.
Oxalic acid anhydrous (CAS No. 144-62-7) stands out as a multifunctional organic acid with significant industrial, scientific, and practical value. Its strong acidity, reducing capabilities, and ability to form stable complexes make it indispensable in metal treatment, textile processing, pharmaceutical synthesis, and wood restoration. However, its reactive nature requires careful handling, proper storage, and respect for safety procedures.
As industries continue to seek efficient and versatile chemical agents, oxalic acid anhydrous remains a widely used compound with expanding applications. Understanding its chemistry and responsible usage ensures both effective results and safety in professional and personal environments.