Oxalic Acid[3]

Updated: 2026-09-20

Overview

Oxalic acid is an organic compound belonging to the carboxylic acid family, first isolated from wood-sorrel plants. In industrial contexts, it's primarily manufactured through the oxidation of carbohydrates or ethylene glycol. The compound exists as a dihydrate in its most common commercial form. Industrial-grade oxalic acid is distinguished by its high purity (typically 99.6% minimum) and consistent crystal structure. As one of the strongest organic acids, oxalic acid plays crucial roles across multiple industries. Its ability to form stable complexes with metal ions makes it particularly valuable for cleaning and surface treatment applications. The compound is produced globally, with major manufacturing centers in China, India, and Europe.

Physical and Chemical Properties

Oxalic acid exhibits distinctive physical characteristics including a rhombic crystal structure in its dihydrate form and an orthorhombic structure when anhydrous. The compound sublimes at temperatures above 150°C and decomposes before reaching its boiling point, releasing carbon monoxide and carbon dioxide. Chemically, it's classified as a reducing agent with a standard redox potential of -0.49V. The acid's most notable chemical property is its strong chelating ability, particularly with iron and calcium ions. This characteristic underpins many of its industrial applications. Oxalic acid forms two series of salts: acid oxalates (hydrogen oxalates) and neutral oxalates, with the latter being generally insoluble except for alkali metal and ammonium oxalates.

Main Applications

In metal treatment industries, oxalic acid serves as an effective rust remover and surface preparation agent, particularly for stainless steel and aluminum. Its reducing properties make it valuable in rare earth element extraction processes. The textile industry utilizes oxalic acid as a bleaching agent for wood pulp and natural fibers, as well as a mordant in dyeing processes. Other significant applications include its use as a pH regulator in pharmaceutical manufacturing, a cleaning agent in food processing equipment (followed by thorough rinsing), and a component in certain automotive cooling system cleaners. In niche applications, oxalic acid finds use in beekeeping as a varroa mite treatment and in photography as a developing agent.

Safety and Storage

Oxalic acid requires careful handling due to its corrosive nature and systemic toxicity. Proper personal protective equipment including chemical-resistant gloves, eye protection, and respiratory equipment should be used when handling the powder or concentrated solutions. The substance is particularly hazardous if ingested, as it can combine with calcium to form insoluble calcium oxalate, potentially leading to hypocalcemia and kidney damage. Storage should be in tightly sealed containers made of polyethylene or other acid-resistant materials, kept in cool, dry conditions separate from bases, oxidizing agents, and food products. Spills should be neutralized with alkaline materials (such as sodium bicarbonate) and cleaned promptly with adequate ventilation. Facilities should maintain eyewash stations and safety showers in areas where oxalic acid is handled.

B2B Procurement Guide

When sourcing industrial oxalic acid, buyers should specify required parameters including purity (typically 99.6% min), crystal size (for applications where dissolution rate matters), and packaging preferences (25kg woven bags with PE liner being most common). Technical specifications should include limits on heavy metal content, sulfate ash, and moisture content. Quality verification can include certificates of analysis from manufacturers and third-party testing for critical applications. Bulk purchasers should inquire about tanker truck or container loading options for cost savings. Logistics planning should account for oxalic acid's classification as a Class 8 corrosive material during transportation. Establishing relationships with manufacturers rather than trading intermediaries often yields better pricing and more consistent quality assurance.