How Oxalic Acid Is Used in Industry, Cleaning, and Science
Oxalic acid, which is otherwise known as ethanedioic acid, is a colorless, crystalline, organic compound from the dicarboxylic acid family found in many plants. It is widely used in laundry to effectively remove ink stains and in industries for the removal of rust. For the same reason, it is the main component of many commercial preparations used to remove scale from car radiators.
The chemical formula of Oxalic acid is given by C2H2O4. Under standard temperature and pressure (STP) conditions, oxalic acid is present as a white crystalline solid. When dissolved in water, this compound is known to form a colorless solution. Oxalic acid is considered to be the simplest dicarboxylic acid because it is composed of two carboxyl groups.
Uses of Oxalic Acid
1. Removing marks, stains and rust
As mentioned above, oxalic acid is mainly used for the most demanding cleaning operations. Oxalic acid effectively removes all kinds of marks and stains from the surface of the object. It is a gentle stain remover that eats up stains but leaves the base as it is. Acids have similar properties to bleach and can be used, for example, to remove rust on metals such as plumbing pipes, kitchen countertops etc. Some cleaning agents, laundry detergents, and bleaches contain some of this acid. Oxalic acid is also ideal for polishing virtually all stones and disposing of waste wood.
2. Industrial use
In industry, this chemical is primarily used in mineral processing mechanisms. In addition, oxalic acid can be used to sterilize equipment, and people in the textile industry use it to bleach clothes. It is also used in factories for removing rust from metallic equipment.
3. Medical use of oxalic acid
In the medical field, companies use acids to further purify or dilute certain chemicals. However, there is little data on the health benefits of this acid. Oxalic acid in both organic and raw forms is not fatal. But sometimes it can have harmful effects on the body.
4. Reducing and treating element
Oxalic acid is mainly used as a reducing element in the development of photographic film. This acid is also used in wastewater treatment plants to effectively remove lime from water.
What Acid is Used to Remove Rust?
To remove the rust for the products like iron, some strong acids will be helpful.
Strong alkalis and strong acids can remove rust quickly. However, these caustic chemicals pose various safety and health risks and require that the user observe strict safety precautions. Strong acids will dissolve rust, but these strong acids will also dissolve paint, finishes, and sometimes even the metal itself. Hydrochloric acid (which is otherwise known as muriatic acid when it is in diluted form), also phosphoric acid, sulfuric acid can be used as a rust removal formula using these strong acids. These strong acids are mineral acids, and especially in concentrated forms, they are highly corrosive. Strong alkalis work in the same way, but on the opposite end of the pH spectrum.
Strong acids work by dissolving rust. Most of the acid-based rust removal products are of gel formulations. If that gel remains on the metal too long after the gel is applied, it starts dissolving it, causing pitting. While on the other side, mineral acids clean away the outer layer of rust, and also they put the underlying metal in a reactive state, making it susceptible to "flash rusting," except it is otherwise neutralized or sealed.
Oxalic Acid Application
There are many oxalic acid applications that we can take from various sources. Up to 25% of oxalic acid produced will be used as a mordant in dyeing processes. It is used as bleach, especially for pulpwood. Also, it is used in baking powder and as the third reagent in silica analysis instruments.
The oxalic acid application or the uses of oxalic acid in daily life are given below.
Cleaning
Oxalic acid application mainly includes bleaching or cleaning, especially oxalic acid as a rust remover (an iron complexing agent). Its utility in rust removal agents is because it forms a stable, water-soluble salt with ferrioxalate ion and ferric iron.
Extractive Metallurgy
Oxalic acid is a primary reagent in lanthanide chemistry. Hydrated lanthanide oxalates readily form in very strongly acidic solutions in easily filtered form, a densely crystalline, and as largely free of contamination by non-lanthanide elements. This oxalate thermal decomposition gives the oxides, the most commonly marketed form of these elements.
Niche Uses:
Oxalic acid is also used by a few beekeepers as a miticide against the parasitic varroa mite
This acid is used to clean minerals.
Oxalic acid is also sometimes used in the aluminum anodizing process, with or without sulfuric acid. Compared to the sulfuric acid anodizing, the coatings obtained are thinner and exhibit a lower surface roughness.
Physical Properties of Oxalic Acid
The molecular weight of anhydrous oxalic acid is 90.034 grams per mole. The molecular weight of the dihydrate of this organic compound is equivalent to 126.065 grams per mole.
Under standard conditions, oxalic acid exists as an essentially crystalline white solid and is odorless.
The density of anhydrous oxalic acid is 1.90 grams / cubic centimeter. The density of oxalic acid dihydrate is 1.653 grams per cubic centimeter.
Oxalic acid is very soluble in water. The solubility of this organic compound in water ranges from 90 to 100 grams per liter at a temperature of 20 degrees Celsius.
It is soluble in both ethanol and diethyl ether.
Precautions to be Taken
The pure form of oxalic acid is extremely toxic and corrosive and should be handled with care. Always wear latex gloves to protect your skin when mixing powdered acids with water. You should also use protective goggles and gas masks to prevent eye irritation and prevent harmful smoke from entering your lungs. Always mix oxalic acid in a well-ventilated area such as open ground, preferably far from residential localities. If swallowed by mistake, do not induce vomiting instead immediately contact your doctor, nearest hospital or local poison control center.
FAQs on Oxalic Acid: Real-World Uses & Applications
1. What is oxalic acid and what are its main uses in daily life?
Oxalic acid, with the chemical formula C₂H₂O₄, is a naturally occurring dicarboxylic acid. In daily life, it is a versatile compound primarily used as a powerful cleaning and bleaching agent. Its key applications include removing stubborn rust stains from metal surfaces, cleaning mineral deposits, and brightening wood decks and furniture by removing graying caused by weathering.
2. How is oxalic acid used industrially for bleaching and metal treatment?
In industrial settings, oxalic acid has several important applications based on its chemical properties:
- Bleaching Agent: It is widely used in the textile industry to bleach fabrics and in the processing of wood pulp to lighten its colour for paper manufacturing.
- Metal Treatment: It serves as a rust remover and cleaning agent for metal equipment and machinery. It is also used in preparing metal surfaces for coatings and in the purification of rare-earth metals by precipitating their oxalates.
- Dyeing Mordant: It acts as a mordant in the dyeing process, helping the dye to bind effectively to the fabric fibres.
3. What is the role of oxalic acid in a chemistry laboratory?
In a chemistry lab, oxalic acid is a crucial reagent with several uses. Its primary role is as a primary standard in analytical chemistry for standardising solutions of oxidising agents like potassium permanganate (KMnO₄) through redox titrations. It is also used in the synthesis of other organic compounds and for cleaning laboratory glassware by removing iron oxide and other mineral stains.
4. Why is oxalic acid such an effective rust remover compared to other common acids?
Oxalic acid's effectiveness as a rust remover stems from its ability to act as a chelating agent. Rust, which is primarily hydrated iron(III) oxide (Fe₂O₃·nH₂O), is insoluble in water. Oxalic acid reacts with the insoluble iron(III) ions to form a stable, water-soluble complex ion, ferric oxalate ([Fe(C₂O₄)₃]³⁻). This process effectively lifts the rust from the surface into the solution, allowing it to be easily washed away. Unlike simple acids that just dissolve rust, chelation is a more efficient and targeted mechanism.
5. Since oxalic acid is found in vegetables like spinach, is it safe for consumption?
While oxalic acid is present in many plant-based foods like spinach, rhubarb, and beets, the concentrations are generally low enough to be safe for most people in moderation. The body can process these small amounts. However, in high concentrations, oxalic acid can bind with calcium in the digestive tract to form calcium oxalate, which is insoluble and can contribute to the formation of kidney stones in susceptible individuals. Therefore, while foods containing oxalates are part of a healthy diet, excessive consumption is not recommended for those prone to kidney issues.
6. What makes oxalic acid a stronger acid than acetic acid, and how does this property influence its uses?
Oxalic acid is significantly stronger than acetic acid due to the inductive effect. Oxalic acid has two carboxylic acid (-COOH) groups. The highly electronegative oxygen atoms in one group pull electron density away from the other, stabilising the conjugate base (oxalate ion) that forms after donating a proton. This stabilisation makes the proton easier to release. This greater acidity makes oxalic acid more effective for applications requiring a stronger reaction, such as dissolving stubborn mineral deposits and acting as a more potent catalyst or reagent in chemical synthesis compared to weaker acids like acetic acid.
7. What safety precautions are necessary when handling oxalic acid, especially for household cleaning?
Although it is a naturally occurring acid, concentrated oxalic acid is corrosive and toxic. When using it, it is crucial to take the following safety precautions:
- Protective Gear: Always wear chemical-resistant gloves, safety goggles, and a mask to prevent skin contact, eye damage, and inhalation of its dust or fumes.
- Ventilation: Work in a well-ventilated area to avoid breathing in airborne particles or vapours.
- Dilution: Follow the recommended dilution instructions carefully. Always add acid to water, never the other way around.
- Storage and Disposal: Store it away from children and pets, and dispose of it according to local regulations for hazardous chemicals.
