Oxalic Acid (Ethane-1,2-dicarboxylic Acid): Product Overview and Practical Tips

I. Product Introduction: What Is Oxalic Acid?

Oxalic acid, also known as ethane-1,2-dicarboxylic acid, has the molecular formula C₂H₂O₄ and is the simplest dicarboxylic acid. It typically exists as colorless, transparent crystals or a white crystalline powder; it is odorless and has a very sour taste. Natural oxalic acid is widely found in plants such as spinach, rhubarb, sugar beets, and cocoa, but industrially, it is primarily produced through synthetic methods. The oxalic acid products we supply have a purity of up to 99.99%, meeting the stringent quality requirements for raw materials in high-precision and high-tech applications. Oxalic acid possesses strong acidity, as well as reducing and chelating properties, making it essential in various industries including chemicals, pharmaceuticals, electronics, and metal processing. As a professional chemical trading company, we are committed to providing our customers with high-quality oxalic acid products that comply with international standards.

II. Key Physical and Chemical Properties and Specifications

The specific specifications of the oxalic acid products we provide are as follows: The Chinese name is Oxalic Acid (Ethane-1,2-dicarboxylic Acid), with a purity of 99.99%. Please note that the CAS number for this product is 6153-56-6, which corresponds to oxalic acid dihydrate (C₂H₂O₄·2H₂O), whereas the CAS number for common anhydrous oxalic acid is 144-62-7. The EINECS number is 205-634-3, and the molecular weight is 90.04 (based on the anhydrous form). Oxalic acid is highly soluble in water, slightly soluble in ethanol, and insoluble in diethyl ether. Its aqueous solution is distinctly acidic; when heated, it decomposes to form products such as carbon monoxide, carbon dioxide, and formic acid. Oxalic acid possesses strong chelating ability and can form stable, soluble complexes with various metal ions; this property is one of the foundations for its widespread application.

III. Major Uses of Oxalic Acid

Oxalic acid plays a key role in numerous industrial sectors. In the metal surface treatment industry, oxalic acid is widely used for rust removal and polishing; it chelates with trivalent iron ions in rust, thereby effectively removing oxides from metal surfaces. In the extraction and separation of rare earth elements, oxalic acid is commonly used as a precipitant, causing rare earth ions to precipitate in the form of oxalates, thereby enabling separation and purification. In the textile and leather industries, oxalic acid serves as a bleaching agent and mordant, capable of removing rust and ink stains from clothing. In the pharmaceutical industry, oxalic acid serves as an intermediate in the synthesis of various drugs, such as sulfonamides and vitamin B6. Additionally, it is a key raw material for producing oxalates (e.g., calcium oxalate and ferrous oxalate) and can be used to prepare antimicrobial agents, antifungal agents, and high-purity electronic chemicals.

IV. Fun Facts: Oxalic Acid in Daily Life and Safety Precautions

Many people have actually come into contact with oxalic acid in their daily lives: it is the source of the “astringent taste” in vegetables such as spinach. The bitterness and astringency of vegetables diminish after blanching, which is precisely the result of some of the oxalic acid dissolving in water. Calcium oxalate is one of the most common components of kidney stones. Therefore, patients with urinary tract stones should be mindful of their intake of high-oxalate foods and should consume them with plenty of water and high-calcium foods to reduce intestinal absorption of oxalic acid. Another interesting fact is that oxalic acid can be used to remove stubborn limescale from stainless steel kettles. By dissolving a small amount of oxalic acid, heating it, and soaking the kettle, the calcium carbonate in the limescale reacts with the oxalic acid to form soluble calcium oxalate, which is then dissolved. However, it is important to note that oxalic acid itself is corrosive and toxic; accidental ingestion or skin contact can cause harm. When removing scale at home, oxalic acid must not be mixed with chlorine-based cleaners, as this may produce toxic gases. Wear rubber gloves and safety goggles during use, and rinse thoroughly afterward.

V. Production Processes and Purification Technologies

Industrial production of oxalic acid primarily follows two routes: the sodium formate method and the carbohydrate oxidation method. The sodium formate method involves reacting carbon monoxide with sodium hydroxide to produce sodium formate, which is then dehydrogenated at high temperatures to form sodium oxalate, and finally acidified to yield oxalic acid. This process is well-established and suitable for large-scale production. The carbohydrate oxidation method uses starch, glucose, and other carbohydrates as raw materials, which are oxidized with nitric acid in the presence of a vanadium catalyst to produce oxalic acid in a single step. For high-purity oxalic acid requiring a purity of 99.99%, additional purification steps such as multi-stage recrystallization, ion exchange, or distillation are necessary to remove metallic impurities (e.g., iron, copper, calcium, and lead) as well as anionic impurities (e.g., nitrate and chloride ions). Our company employs advanced purification processes to ensure that the content of metallic impurities in our products is controlled to below the ppm level, meeting the requirements of high-end applications such as electronic-grade and analytical-grade oxalic acid.