Oxalic Acid: Structure, Formula & Uses

Instructor: Artem Cheprasov

Artem has a doctor of veterinary medicine degree.

Vitamin C, bees, and rust have something in common: oxalic acid. Find out how in this lesson on oxalic acid's structure, formula, and uses, and learn about some example chemical reactions involving the substance.

Oxalic Acid

Eat your veggies! Why? It's because veggies have a lot of important vitamins. One of them is vitamin C, also known as ascorbic acid. Your body actually turns this ascorbic acid into another compound called oxalic acid, also known as ethanedioic acid. If you are one of those people who pops massive doses of vitamin C thanks to Linus Pauling, you should be careful. That's because too much oxalic acid might contribute to the formation of calcium oxalate (the calcium salt of oxalic acid) kidney stones. Ouch!

But don't worry, this lesson won't be painful. Read on to learn more details about oxalic acid's structure, formula, and properties and some of its cool uses.

Structure, Formula & Properties

Oxalic acid can be symbolized by the following two molecular formulas:


Here, the C stands for carbon, the H stands for hydrogen and the O represents oxygen. The structure of oxalic acid can be shown through visual models as well.

The 2D structure of oxalic acid.

The 3D structure of oxalic acid.

Oxalic acid has numerous chemical and physical properties:

  • It's colorless
  • It's odorless
  • It's a powder or granular solid at room temperature
  • Its crystals can have a pyramidal shape to them

In addition, oxalic acid can react violently with things like alkali metals. It is also sensitive to heat, and it is potentially explosive when mixed with certain compounds.

Interestingly, a colorful oxidation reduction reaction occurs when potassium permanganate is mixed with oxalic acid. The reaction turns the purple potassium permanganate into a light brown color.


Oxalic acid itself can be made by numerous methods. One way is to heat sodium formate in the presence of sodium hydroxide. It can also be made via the nitric acid oxidation of ethylene glycol (ethylene glycol is famous for being an ingredient in antifreeze).


Regardless of how it's made, oxalic acid has many uses. Are you someone who works with a lot of rusty metal? Or, perhaps you work with ink? Oxalic acid to the rescue! It can be used in laundry facilities as an acid rinse that helps to get of rust and ink stains. The oxalic acid chemically reacts with the rust and ink makes it much easier to wash the stains away.

Various substances, such as dimethyl oxalate, can be produced through the esterification of oxalic acid in order to create compounds for other uses, such as as chelating agents in the cosmetics industry.

Likewise, phosphoryl chloride can be made when reacting oxalic acid with phosphorus pentachloride, and this can be used to help make flame retardants.

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