CAS 144-62-7 · Simplest Dicarboxylic Acid · Solid
Oxalic Acid
C₂H₂O₄ · MW 90.03 g/mol · Ethanedioic Acid
The simplest dicarboxylic acid — a white crystalline solid with strong chelating and reducing properties. Oxalic acid's ability to form stable complexes with iron and other metals makes it the go-to choice for rust removal, metal cleaning, and bleaching applications where mineral acids would be too aggressive. Texas-Chem supplies oxalic acid in industrial and ACS grades in bags, drums, and super sacks.
Formula
C₂H₂O₄
Melting Point
189–191 °C
pKa₁
1.25
Form
Crystalline Solid
Structural Formula
Two carboxylic acid groups joined directly — strong chelating agent for iron and heavy metals
Safety & Regulatory
- NFPA Health
- 3 — Serious hazard
- NFPA Flammability
- 1 — Slight hazard
- NFPA Reactivity
- 0 — Stable
- OSHA PEL (TWA)
- 1 mg/m³
- ACGIH TLV-TWA
- 1 mg/m³
- DOT Hazard Class
- 8 — Corrosive (solid)
- UN Number
- UN 2449 (solution) / Not regulated (solid <3%)
- Special Hazard
- Toxic if ingested — causes kidney damage (oxalate crystals)
Toxic if ingested — do not confuse with food-grade acids. Avoid dust inhalation. Always consult the current Safety Data Sheet before handling.
Grades & Packaging
Available Grades
Pack Sizes
Physical & Chemical Properties
| Molecular Formula | C₂H₂O₄ (HOOC–COOH) |
| Molecular Weight | 90.03 g/mol |
| CAS Number | 144-62-7 |
| Physical Form | White crystalline solid (dihydrate or anhydrous) |
| Melting Point | 189–191 °C (anhydrous); 101 °C (dihydrate) |
| Boiling Point | 365 °C (decomposes) |
| Flash Point | Non-flammable |
| Density | 1.90 g/cm³ (anhydrous) |
| Solubility in Water | 90 g/L at 20 °C; 250 g/L at 80 °C |
| pKa₁ | 1.25 |
| pKa₂ | 4.27 |
| Odor | Odorless |
Industrial Applications
Metal Cleaning & Rust Removal
Oxalic acid dissolves iron oxides (rust) by forming soluble iron oxalate complexes. Widely used for cleaning iron and steel surfaces, radiators, and industrial equipment without attacking the base metal aggressively.
Textile & Leather Bleaching
Reducing bleach for natural fibers, wool, and leather — oxalic acid removes iron stains, tannin discoloration, and yellowing from fabrics without the harshness of chlorine bleaches. Also used in wood bleaching and restoration.
Marble & Stone Polishing
Polishing and restoration agent for marble, limestone, and travertine. Oxalic acid reacts with calcium carbonate to form calcium oxalate, creating a hard, polished surface layer that resists staining.
Rare Earth & Metal Precipitation
Precipitating agent in hydrometallurgy — oxalic acid selectively precipitates rare earth elements, thorium, and other metals as insoluble oxalates from leach solutions, enabling separation and recovery.
Wastewater Treatment
Reducing agent for hexavalent chromium (Cr⁶⁺) in industrial wastewater. Oxalic acid reduces Cr⁶⁺ to the less toxic Cr³⁺ form, which can then be precipitated and removed from effluent streams.
Pharmaceutical & Chemical Synthesis
Intermediate in the synthesis of oxalate salts, esters, and specialty chemicals. Oxalic acid is used to produce calcium oxalate, ferrous oxalate, and as a reagent in analytical chemistry for standardizing permanganate solutions.
Why Source Oxalic Acid from Texas-Chem?
- 35+ years supplying specialty acids and solid chemicals to Texas industry
- Industrial and ACS reagent grades available
- 50-lb bags, 100-lb drums, and super sacks for bulk orders
- Competitive pricing backed by top-tier producer relationships
- Technical support and SDS documentation with every order
- Same-day quotes for standard quantities
Oxalic Acid vs. Alternatives
Oxalic acid is a dicarboxylic acid with strong chelating and reducing properties, widely used in cleaning, bleaching, and metal treatment.
| Attribute | Oxalic Acid | Citric Acid | Acetic Acid |
|---|---|---|---|
| pKa (first) | 1.25 (relatively strong organic acid) | 3.13 | 4.76 |
| Reducing Agent | Yes — strong reducing properties | Mild | Yes — strong |
| Primary Use | Rust removal, bleaching, metal treatment | Food, pharma, cleaning | Descaling, cleaning, metal treatment |
| Physical State | White crystalline solid (anhydrous or dihydrate) | White crystalline solid | White crystalline solid |
| Toxicity | Moderate — toxic by ingestion | Very low — food-safe | Low — mild irritant |
Industries We Supply Oxalic Acid To
Metal Cleaning & Rust Removal
Oxalic acid dissolves iron oxides and rust without attacking base metal, making it ideal for rust removal from steel, cast iron, and stone surfaces.
Oxalic Acid supply in Houston, TXTextile & Leather
Used as a bleaching agent for natural fibers, a stripping agent for dyes, and a mordant in textile dyeing and leather tanning operations.
Oxalic Acid supply in Dallas, TXWood & Stone Restoration
Oxalic acid removes tannin stains, iron stains, and weathering discoloration from wood decks, stone, and masonry surfaces.
Oxalic Acid supply in Fort Worth, TXPharmaceutical & Chemical Synthesis
Used as a precipitating agent for rare earth metals and as an intermediate in the synthesis of pharmaceuticals and specialty chemicals.
Oxalic Acid supply in Beaumont, TX