Industrial Grade Dihydrate Oxalic Acid Crystal CAS NO 6153 56 6 For Chemical Raw Materials

• Chemical formula: C₂H₂O₄*2H₂O
• CAS: 6153-56-6
• Purity: 99.6%

Oxalic acid is an organic acid with the systematic name ethanedioic acid and chemical formula HO−C(=O)−C(=O)−OH, also written as (COOH)2 or (CO2H)2 or H2C2O4. It is the simplest dicarboxylic acid. It is a white crystalline solid that forms a colorless solution in water.

Its name is derived from early investigators who isolated oxalic acid from flowering plants of the genus Oxalis, commonly known as wood-sorrels. It occurs naturally in many foods. Excessive ingestion of oxalic acid or prolonged skin contact can be dangerous.

• Molecular weight: 126.07 g/mol
• Appearance: White transparent crystal or powder (industrial products may be slightly yellow due to impurities)
• Odor: Tasteless or slightly sour
• Density: 1.65 g/cm³ (20°C)
• Melting point: The dihydrate loses crystalline water at 101-102°C, converting to anhydrous oxalic acid (H₂C₂O₄)
• Solubility: Water (10 g/100 mL at 20°C), slightly soluble in ethanol (5.7g/100 mL at 20°C)
• Acidity: Stronger than acetic acid (pKa₁=1.25, pKa₂=4.14)
• Reducibility: Can be oxidized by strong oxidants under acidic conditions
• Complexation: Forms soluble complexes with metal ions (e.g. Fe³+, Al³+)

Oxalic acid is produced primarily by oxidizing carbohydrates or glucose with nitric acid or air in the presence of vanadium pentoxide. Another method is to regenerate nitric acid using oxygen, using a variety of precursors, including glycolic acid and glycol.

A newer method requires oxidative carbonylation of alcohols to obtain dioxalate: 4 ROH + 4 CO + O₂ → 2 (CO₂R)₂ + 2 H₂O. These diesters are then hydrolyzed to oxalic acid. About 120,000 tons are produced annually.

The main uses of oxalic acid include:

• Cleaning or bleaching, especially for rust removal (iron complexing agent)
• Ingredient in some teeth whitening products
• Mordant in dyeing processes (25% of usage)
• Bleaching wood, cork, straw, rattan, and feathers
• Baking powder additive
• Reagent in silica analysis instruments

Uses in cleaning ores:

• Remove iron oxides by forming soluble iron oxalate complexes
• Dissolve carbonate gangue (calcite, dolomite) to form soluble oxalates
• Clean quartz or silicate ores by removing residual metal oxides

Operating Steps (Example):

1. Prepare 5-10% oxalic acid solution (heating to 50-60℃ enhances efficiency)
2. Soak ore for several hours to 24 hours or scrub surface stains directly
3. Neutralize with sodium bicarbonate solution before thorough rinsing

Precautions:

• Applicable for iron oxides and carbonate impurities, not for sulfide ores
• Requires safety equipment (gloves, goggles, gas mask when heated)
• Waste liquid must be treated as hazardous waste
• Consider alternatives (hydrochloric acid, citric acid) if effectiveness is limited