Oxalic Acid

What is Oxalic Acid?

Oxalic acid is a white, colourless crystalline solid with the chemical formula; C2H2O4. It is highly soluble in water and ethanol and occurs naturally in many plants and foods such as in rhubarb leaves, spinach and almonds. It is a reducing agent and is a slightly stronger acid than phosphoric acid.   

What is Oxalic Acid used for?

Oxalic Acid is a reducing agent with major uses in; textile finishing (stripping cleaning, calico printing, dyeing), cleaning (rust stain removal for metal and equipment cleaning), timber bleach, dye production (in the paper, ceramics, photography and rubber industries). Of the uses mentioned, use as a cleaning agent is how oxalic is mostly used due to its effective bleach-like abilities to remove stains and rust from metals, fabrics and even woods. It is found in many cleaning products, such as detergents and bleaches for these reasons. 

The corrosive properties of oxalic acid makes it effective at removing rust from metal.
The corrosive properties of oxalic acid makes it effective at removing rust from metal.

Oxalic Acid Hazards

The routes of exposure for oxalic acid include; inhalation, ingestion and skin and eye contact. 

Inhalation of oxalic acid may produce irritation and inflammation of the respiratory system. Inhalation of oxalic acid dusts can cause; ulceration of the membranes in the nose and throat, nosebleeds, headaches, nervousness, coughing, vomiting, emaciation, back pain and weakness. Those with already compromised respiratory function (conditions such as emphysema or chronic bronchitis), may suffer further disability upon inhalation. Additionally, people with prior damage to their kidneys, circulatory or nervous systems should be screened prior to handling to reduce the risk of further damage caused by the chemical. 

Animal experiments suggest that ingestion of oxalic acid may be seriously harmful to the health of the individual. The corrosive nature of the acid may cause immediate pain in the mouth with difficulties swallowing and speaking also evident. Other symptoms include respiratory distress, nausea, vomiting, diarrhoea and possibly asphyxia. Ingestion of 5 grams has caused death within hours, with symptoms of poisoning including vomiting, pain, weak/irregular pulse, headaches, muscular cramps and occasionally a coma.

Skin contact with oxalic acid may be harmful with additional systemic health effects following absorption. Solutions of 5-10% oxalic acid are irritating to the skin after prolonged contact and early gangrene can occur after hand immersion in oxalate solutions. Lesions on the skin may follow exposure to the chemical and entry into the bloodstream through open cuts or wounds may produce other harmful effects.

Direct eye contact with oxalic acid may produce pain and burns. Mild burns generally recover quickly and fully, however severe burns can produce lasting and possibly irreversible damage (i.e. blindness). 

Oxalic Acid Safety

If inhaled, remove the patient from the contaminated area to the nearest fresh air source and monitor their breathing. Lay them down and keep them warm and rested. If the patient is not breathing and you are qualified to do so, perform CPR. Seek medical attention without delay. 

If swallowed, do not induce vomiting. If vomiting does occur, lean the patient forward or place them on their left side to maintain open airways and prevent aspiration. Give them water to rinse their mouth out and provide as much as they can comfortably drink. Observe the patient carefully as urgent hospital treatment is likely to be required. 

If skin exposure occurs, immediately remove all contaminated clothing, footwear and accessories and cleanse the affected area with plenty of water until advised to stop by the Poisons Information Centre. Seek medical attention. 

If the chemical is exposed to the eyes, flush the eyes out immediately with fresh running water for at least 15 minutes, remembering to wash under the eyelids. Removal of contact lenses should only be done by a skilled individual. Seek medical attention without delay.

Contact lenses can worsen the symptoms of chemical exposure to the eye.
Contact lenses can worsen the symptoms of chemical exposure to the eye.  

Oxalic Acid Safety Handling

Emergency eyewash fountains and safety showers should be accessible in the immediate area of the potential exposure to the chemical and adequate ventilation should be available (install local exhaust if necessary).

The PPE recommended when handling oxalic acid includes; safety glasses with unperforated side shields, chemical goggles, full face shields or gas masks, elbow length PVC gloves, overalls, PVC aprons, PVC protective suits (in cases of severe exposure) and boots.

Refer to your SDS for more comprehensive information on the safe handling of oxalic acid.