4 Uses for Oxalic Acid

Oxalic acid is an essential household chemical that can be used, like many acids, as a cleaner for various things such as a rust remover, a cleaning agent, a stain lifter on woodwork, and as a bleaching agent.

This acid is a natural component of plants and vegetables such as buckwheat and rhubarb and is available for purchase in powdered form at your local home improvement depot. The oxalic powder is then mixed with water to turn into a solution of oxalic acid. At high doses, oxalic acid is very dangerous, but at moderate doses, it is safe for various useful functions.

1. Bleaching

Oxalic acid can be used as a bleaching agent for both wood and stone. Wood, when exposed to the elements, can turn gray. When oxalic acid is applied on an old and graying wood floor, it brings back the wood floor’s natural white color. As a result, this acid is often used when preparing to stain old wood floors. It is also used by furniture manufacturers to lighten heavily stained areas of wood furniture in preparation for refinishing.

2. Removing Stains

Oxalic acid effectively removes ink, food stains, and many other types of stains. It is a gentle stain remover that eats the stain but leaves the base surfaces, such as wood, intact. You can use oxalic acid to remove most stains found on stone, brick, linoleum, wood, and vinyl surfaces.

Do not, however, use oxalic acid if your flooring is sealed as it will eat through the finishing.

Although you can also use oxalic acid to remove stains from fabrics such as linen and cotton, it will take a lot of time, so it is better to have your fabrics dry cleaned instead.

3. Removing Rust

Oxalic acid is also used to remove rusts that are commonly found on plumbing pipes and kitchen countertops, and is a major ingredient found in commercial rust removers for sinks, tubs, and rust stains.

4. Other Uses

Aside from bleaching, rust removing, and stain removing, oxalic acid is also used as a reducing agent in developing photographic film. You can also find it used in wastewater treatment as well since oxalic acid can effectively remove calcium from wastewater. Oxalic acid is also used as a grinding agent when polishing marble.

Safety Precautions

Oxalic acid in its pure form is very dangerous. It is toxic and corrosive and should be carefully handled. When mixing the powdered acid with water, always wear latex gloves to protect your skin. You should also use protective glasses and a dust mask to avoid eye irritation and to prevent the noxious fumes from getting into your lungs.

Always mix oxalic acid in an area that is well-ventilated—preferably outdoors. In case of accidental swallowing, never induce vomiting; instead, contact your physician or your local poison control center immediately.

Oxalic Acid FAQ

What is the everyday use of oxalic acid?

Oxalic acid is a cleaning agent that can be used for tough jobs, such as removing rust stains. You will find it often included in the ingredient list for laundry detergents and bleaches, but these are small amounts.

Can you clean a toilet with oxalic acid?

Oxalic acid is especially useful against tough stains, including limescale. It can definitely be used to remove tough stains from the toilet.

Is oxalic acid safe for humans?

Because oxalic acid is colorless but poisonous, it is dangerous. Colorless acid looks harmless and this is not, so you need to be extremely cautious with this.

Oxalic acid can cause severe damage to the skin because it is an acid. It should not come into contact with skin or soft tissues and if it does, you need to get medical attention immediately.

Can you pour oxalic acid down the drain?

Oxalic acid can be poured down the drain but only with copious amounts of water. Flush the acid down the drain very well with a lot of water and not only will the oxalic acid be disposed of but it will also remove mineral deposits in pipes to help prevent clogs.

Does baking soda react with oxalic acid?

Baking soda reacts with many cleaning agents, including vinegar and lemon juice, but has no reaction with oxalic acid. Only when water is added to the two ingredients do they begin to react.