Oxalic acid

Oxalic acid, with the chemical formula H₂C₂O₄, is an organic dicarboxylic acid widely found in nature (such as in plants like spinach and rhubarb) and is also a metabolic byproduct of many organisms. Here is key information about oxalic acid:

1. Basic Properties

- Physical properties: Colorless transparent crystals or white powder, soluble in water, with a sour taste.

- Chemical properties:

  - Strong acidity (pKa₁=1.25, pKa₂=4.14), capable of forming insoluble salts with metal ions (e.g., calcium oxalate, CaC₂O₄).

  - Exhibits reducing properties and can be oxidized by KMnO₄, commonly used in chemical titrations.

  - Decomposes upon heating to produce carbon dioxide (CO₂), carbon monoxide (CO), and water (H₂O).

2. Common Uses

- Industrial applications:

  - Used as a metal cleaner (to remove rust and ink stains).

  - Bleaching agent (for wood and textiles).

  - Chemical raw material (for synthesizing pharmaceuticals, dyes, etc.).

- Laboratory: Serves as a reducing agent or ligand solution.

- Daily life: Found in small amounts in certain cleaners or descalers.

3. Safety Precautions

- Toxicity: Oxalic acid and its salts (e.g., sodium oxalate) are toxic to humans. Accidental ingestion may cause:

  - Burns to the mouth and digestive tract.

  - Hypocalcemia (due to binding with calcium ions to form calcium oxalate precipitates).

  - In severe cases, kidney stones or kidney failure.

- Protective measures:

  - Avoid direct skin contact or inhalation of dust.

  - Wear gloves and goggles during use, and ensure proper ventilation.

  - Store appropriately, away from children and food.

5. Environmental Impact and Disposal

- Oxalic acid is biodegradable, but high-concentration discharges can pollute water bodies. Dispose of it as chemical waste.