Understanding the Uses and Hazards of Oxalic Acid

Two scientists examining oxalic acid inside a laboratory

Oxalic acid, a crystalline solid that dissolves in water to give colorless, acidic solutions, is an organic compound prevalent in many plants, vegetables, and fruits. From cleaning agents to rust removal, oxalic acid serves numerous purposes across various industries. However, its toxic nature necessitates careful handling and consideration of chemical reaction and its potential impacts on human health.

Scientific Identity of Oxalic Acid

  • Molecular Formula: C₂H₂O₄
  • Scientific Name: Ethanedioic acid
  • Density: 1.90 g/cm³
  • Boiling Point: 185.06°C (365.1°F)
  • Melting Point: 101-102°C (214.7°F)

One of the intriguing characteristics of this substance is its solubility; oxalic acid dissolves well in water, alcohol, and ether, demonstrating its versatility in various solvents. However, it is important to note that its solubility in water uniquely decreases as the temperature rises, setting it apart from numerous other organic acids. This behavior is crucial in certain industrial applications where temperature control is essential.

Oxalic acid possesses two carboxylic acid groups, classifying it as a dibasic acid. This structure allows it to donate two protons during acid-base reactions, highlighting its strength as an acid. Furthermore, its ability to form stable complexes with metal ions makes it invaluable in various industrial processes, including cleaning and metal extraction.

In its solid form, ethanedioic acid usually exists as a dihydrate, which means it is associated with two water molecules. This dihydrate form is essential to consider, especially when calculating molar mass for quantitative chemical reactions. Additionally, it is crucial to handle the oxalic acid dihydrate with care due to its irritating or toxic fumes, ensuring proper safety measures are in place to prevent adverse health effects.

Applications of Oxalic Acid

Industrial Utilization

Oxalic acid is invaluable in various industries, particularly in the textile industry where it acts as a mordant, enhancing the adhesion of dyes to fabric for more vibrant and lasting colors. Beyond textiles, its capacity to form stable complexes with metal ions finds application in numerous processes across different sectors, showcasing its versatility. The acid's role extends to various specialized industrial applications, reflecting its importance in enhancing efficiency and performance.

Cleaning and Maintenance

As a powerful acidic compound, oxalic acid is highly effective in cleaning applications, particularly for eliminating rust and hard-to-remove stains. Users must exercise caution, wearing appropriate personal protective clothing and equipment, and ensuring adequate ventilation, due to the acid’s toxic nature. Its efficacy in stain removal makes it a popular choice for various maintenance tasks.

Agricultural Use

The efficacy of oxalic acid in eradicating mites plays a crucial role in preserving the well-being, vitality, and productivity of beehives, ensuring a stable environment for bees to thrive. Additionally, by contributing to the overall health of bee populations, ethanedioic acid indirectly supports pollination processes, which are important for the flourishing of various ecosystems and agricultural activities. Furthermore, its use as a pest control agent in apiculture highlights the importance of sustainable and effective pest management practices in maintaining balanced and healthy bee communities.

Leather Processing

By effectively cleaning and preparing the hides in leather processing, oxalic acid facilitates the removal of any remaining hair and impurities, ensuring a smoother and more uniform surface. The acid’s involvement in the tanning process also helps to enhance the leather's inherent characteristics, including its flexibility, resilience, and longevity. This results in a product that not only meets industry standards but also satisfies consumer expectations for high-quality, durable leather goods.

Laboratory Applications

In laboratory settings, oxalic acid is used for various analytical purposes. It can act as a reagent in different chemical reactions, aiding scientists in the identification and quantification of various substances. Its properties make it a versatile tool in scientific research and experimentation. Additionally, its extensive applications extend to material synthesis and organic chemistry, showcasing its adaptability and importance in diverse experimental contexts.

Toxicity of Oxalic Acid

Oxalic acid is toxic due to its ability to bind with calcium in the body, forming insoluble crystals that can damage the kidneys and other organs. Ingesting high amounts of harmful concentration of ethanedioic acid or prolonged exposure to harmful concentration can induce vomiting and lead to serious health issues, including kidney damage and even death in severe cases. Awareness and proper handling of hazardous substances are crucial to prevent prolonged skin exposure to harmful concentration of hazardous substances.

Oxalic acid is naturally present in a range of plant-based foods, and while it is not consumed in its pure form due to its irritating or toxic fumes, people ingest small amounts of it as part of their regular diet.

Foods that Contain Oxalic Acid

  • Spinach: A popular leafy green vegetable, spinach has one of the highest concentrations among food items.
  • Beets: Both the root and the leaves (beet greens) contain oxalic acid, though the concentration is higher in the leaves.
  • Potatoes: A staple in many diets, potatoes have a moderate amount.
  • Sweet Potatoes: Like regular potatoes, sweet potatoes also contain ethanedioic acid.
  • Carrots: This commonly consumed vegetable has a lower amount.
  • Celery: Celery is another vegetable that contains oxalic acid, though in smaller amounts.
  • Broccoli: Broccoli has a moderate content and is widely consumed across the globe.
  • Cabbage: This leafy vegetable contains ethanedioic acid, with the amount varying depending on the type of cabbage.
  • Tomatoes: Tomatoes, including all their varieties, have a small amount.
  • Strawberries: Among fruits, strawberries are a source of oxalic acid.

Managing Oxalic Acid Intake

The following are practical solutions that can help in maintaining a balanced oxalic acid intake:

  • Staying Hydrated: Consuming ample amounts of water dilutes the oxalic acid, reducing its potential to form kidney stones.
  • Incorporating Calcium-Rich Foods: Including dairy products and other calcium-rich foods in your diet helps bind oxalic acid in the gut, preventing it from being absorbed into the bloodstream.
  • Diversifying Diet: Eating a variety of foods ensures a balanced intake of nutrients, minimizing the risk associated with high oxalic acid consumption.
  • Smart Cooking Practices: Employing cooking methods that reduce oxalic acid content in food, such as boiling and steaming, promotes safer consumption.

Safety Measures

Identifying Oxalic Acid Hazards

Recognizing the inherent risks associated with the toxicity of oxalic acid is crucial for ensuring safe interaction with this chemical. Pure or high concentration of oxalic acid is highly corrosive and can induce vomiting, inflict severe skin burns upon repeated or prolonged contact with the skin, necessitating immediate medical attention. Additionally, inhaling its vapors or dust can lead to serious respiratory complications, potentially damaging the lungs and respiratory tract.

Safe Handling and Storage Practices

Adopting stringent safety measures is imperative when dealing with oxalic acid hazards to prevent accidents and exposure. Utilizing the appropriate personal protective gear such as gloves, safety goggles, and appropriate protective clothing, is non-negotiable to shield the skin and eyes from repeated or prolonged contact. Ensuring a well-ventilated workspace is equally vital to dissipate any fumes and prevent inhalation risks and induce vomiting.

When it comes to storage, oxalic acid dangers must be kept in covered plastic containers in a secure location, out of reach of children and pets, and away from any food or drink items to avoid accidental ingestion. Regular checks on the storage and covered plastic containers for any signs of damage or leaks are necessary to preclude potential hazards. By adhering to these stringent handling and storage protocols, the risks associated with the toxicity of oxalic acid and hazardous substances can be significantly minimized, paving the way for a safer working environment.

First Aid Guide for Oxalic Acid Exposure

This 10-step first aid response ensures that both bystanders and victims can take immediate action to mitigate the effects of exposure.

  1. Assess the safety of the situation and ensure you are not at risk before attempting to assist the person exposed to oxalic acid dangers.
  2. Dial emergency services immediately, providing them with details of the oxalic acid exposure.
  3. Rinse the immediately flood affected skin area under running water for at least 15 minutes, using a safety shower if available.
  4. Flush the eyes with water or saline solution for at least 15 minutes, holding the eyelids open, and seek medical attention promptly.
  5. Move the person to a place with fresh air immediately if they have inhaled ethanedioic acid vapors or dust, and assist with breathing as necessary.
  6. Rinse the mouth with water and encourage small sips of water if oxalic acid has been ingested, but do not induce vomiting.
  7. Remove any contaminated clothing with the toxicity of oxalic acid, avoiding repeated or prolonged contact, and place it in a sealed plastic bag.
  8. Provide reassurance to the affected person, monitor their condition, and wait for medical help to arrive.
  9. Give emergency responders and medical professionals as much information as possible about the oxalic acid exposure.
  10. Ensure a follow-up medical evaluation for the affected individual to check for delayed effects and to receive further treatment if needed.

Refer to the Safety Data Sheet (SDS) for oxalic acid and any other safety documentation provided in your workplace or by the product manufacturer for the most accurate and specific first aid and safety information.

Oxalic acid is a versatile compound with various applications and a presence in many natural sources. However, its toxic nature cannot be overlooked. While oxalic acid has its uses and is present in many aspects of daily life, it is crucial to handle it safely and be aware of its potential dangers. Responsible use and awareness ensure that the benefits of oxalic acid dihydrate can be enjoyed while minimizing the risks.

Frequently Asked Questions (FAQs)

Is oxalic acid the same as vinegar?

No, oxalic acid is not the same as vinegar. While both are acids, vinegar is acetic acid, which is less toxic and used in food preparation. Oxalic acid is much stronger and more toxic.

What happens if you mix oxalic acid with water?

Mixing oxalic acid with water results in a solution that retains the acid’s properties. It is crucial to add the oxalic acid to the water slowly to prevent any adverse reactions.

What is not to mix with oxalic acid?

It is crucial not to mix oxalic acid with bleach or other strong bases, as it can result in dangerous reactions and the release of irritating or toxic fumes.

What cancels out oxalic acid?

To neutralize oxalic acid, a mild base like baking soda can be used. However, it’s important to do this carefully and preferably under expert guidance to prevent any adverse reactions.

The material provided in this article is for general information purposes only. It is not intended to replace professional/legal advice or substitute government regulations, industry standards, or other requirements specific to any business/activity. While we made sure to provide accurate and reliable information, we make no representation that the details or sources are up-to-date, complete or remain available. Readers should consult with an industrial safety expert, qualified professional, or attorney for any specific concerns and questions.


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Author: Herbert Post

Born in the Philadelphia area and raised in Houston by a family who was predominately employed in heavy manufacturing. Herb took a liking to factory processes and later safety compliance where he has spent the last 13 years facilitating best practices and teaching updated regulations. He is married with two children and a St Bernard named Jose. Herb is a self-described compliance geek. When he isn’t studying safety reports and regulatory interpretations he enjoys racquetball and watching his favorite football team, the Dallas Cowboys.