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VSAT 2022

Ammonium Oxalate: An Overview

In Chemistry, salt is known as a substance made by the reaction between acid and base. Ammonium oxalate is an oxalate salt with ammonium (sometimes as a monohydrate). It is a colourless (white) salt under standard conditions and is odourless and non-volatile. It is the ammonium salt of oxalic acid and occurs in many plants and vegetables. Ammonium oxalate is used as an analytical reagent and general reducing agent. It and other oxalates are used as anticoagulants to preserve blood outside the body. Acid ammonium oxalate (ammonium oxalate acidified to pH 3 with oxalic acid) is commonly employed in soil chemical analysis to extract iron and aluminium from poorly-crystalline minerals (such as ferrihydrite), iron (II)-bearing minerals (such as magnetite), and organic matter.


Ammonium Oxalate

A 2:1 ratio of ammonium and oxalate ions is used to produce the ammonium salt known as ammonium oxalate. It is both an oxalate and an ammonium salt. Other names for it include Ethanedioic acid, diammonium salt, Oxalic acid, and diammonium salt. It can be found in a wide variety of plants and vegetables as well.

Ascorbic acid or glyoxylic acid metabolism in the human body also produces it. It is eliminated in the urine rather than being digested. It serves as a general reducing agent and analytical reagent. Ammonium oxalate is an odourless and colourless crystalline powder.

The compound ammonium oxalate can be found in many distinct kidney stone types. It can also be found in seals, seabirds, and/or bat droppings. Since the higher concentration of ammonium oxalate and urate can be utilised as fungicides and fertilisers for plants, the mixture is rich in nitrogen.


Ammonium Oxalate Formula

The chemical formula for ammonium oxalate is NH4OOCCOONH4. The molecular formula for Ammonium oxalate is C2H8N2O4. Ammonium oxalate as the name suggests contains 2 molecules of ammonia and one molecule of oxalate.


Ammonium Oxalate Solution

To make ammonium oxalate solution, first oxalic acid is dissolved in the desired amount of water and then mixed with the required amount of ammonium. Ammonium oxalate is a solid substance that slowly dissolves and combines in water. Oxalic acid is converted into oxalate ion (C2O4)22- by the dissociation of two acidic hydrogens, which results in the formation of an anion. The molecules include two ammonium ions (NH4)+ in the form of cations, with one ammonium replacing each hydrogen lost.


Ammonium Oxalate Test

Oxalic acid can be determined by using a method such as permanganate titration and atomic absorption. As ammonium oxalate helps in preventing or inhibiting the coagulation of blood plasma; hence, it is used in blood tests to prevent blood coagulation. The lead or calcium ions present in blood as well as other analytes can be measured by complexing this chemical with specific metals.


Structure of Ammonium Oxalate



Structure of Ammonium Oxalate


Ammonium Oxalate Uses

Ammonium oxalate can be used in the following ways:

  • Ammonium oxalate is produced by the metabolism of either glycolic acid or ascorbic acid.

  • It can be used in mineral form as oxammite.

  • It can be utilised as an analytical reagent in various tests.

  • This salt form can also be used as a reducing agent.

  • It can be used as an anticoagulant for preserving blood in the test tube.

  • In textile, it is used for dyeing.

There are some side effects of ammonium oxalate as given below:

  • Ammonium oxalate dust when ingested or inhaled excessively causes systemic poisoning in the body.

  • Ammonium oxalate when comes in contact with the eyes can irritate. Similarly, contact with skin can irritate severe burns.

Molecular Weight of Ammonium Oxalate

The chemical formula of ammonium oxalate is C2H8N2O4.

So, (12×2) + (1×8) + (14×2) + (16×4) =124.1

Thus, the molecular weight of ammonium oxalate is 124.1 g/mol.


Ammonium Oxalate Monohydrate [(NH4)2C2O4]

The molecular weight of ammonium oxalate monohydrate is 142.11 g/mol. Same as ammonium oxalate, it is also used for the detection of lead and calcium. Ammonium oxalate monohydrate is most famously used as a buffering agent. The monohydrate is the main commercial form of ammonium oxalate.

Interesting Facts

  • Ammonium oxalate is an odourless solid. Sinks and mixes slowly with water.

  • Ammonium oxalate is a salt that is made up of ammonium and oxalic acid in the ratio of 2:1. It is colourless, odourless, and soluble in water.

Key Features of Ammonium Oxalate

  • Ammonium oxalate is used to make explosives and metal polishes and in textile dyeing and analytical chemistry.

  • It is used as a buffering agent, anticoagulatory for blood and determination of lead calcium, etc.

  • Calcium chloride solution forms a precipitate of calcium oxalate with ammonium oxalate.

  • Ammonium oxalate is usually acidic in nature. The acidity depends on the amount of oxalic acid present.

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FAQs on Ammonium Oxalate

1. How is Ammonium Oxalate Prepared?

Ammonium oxalate is prepared from the neutralization of an oxalic acid diluted in water. Ammonium hydroxide or ammonium carbonate are used as an ammonium source.


(NH4)2CO3 + H2C2O4 (NH4)22C2O4 + CO2 + H2O


2NH4OH + H2C2O4 (NH4)22C2O42H2O

2. What are the Health Hazards of Ammonium Oxalate?

Ammonium oxalate has many severe health hazards. These are explained below:

  • On ingesting or inhaling the ammonium oxalate dust in excess, it tends to cause systemic poisoning.

  • If it comes in contact with the eyes, it irritates. If it comes in contact with the body or skin, the skin gets irritated and sometimes even severely burned.

  • Ammonium oxalate can be easily absorbed through the skin and irritates immediately and to a greater extent. If a person tends to get exposed to ammonium oxalate and if they notice any signs or symptoms, they should immediately contact a physician.

3. Is Ammonium Oxalate Covalent or Ionic?

Ammonium oxalate molecules tend to have an ionic bond between the oxalate anion and the ammonium cation. Therefore, ammonium oxalate is called an ionic compound. Also, this particular compound tends to have two polyatomic ions. The ammonium cation is known to be a polyatomic ion which is made up of nitrogen and hydrogen. The oxalate anion is also known to be a polyatomic ion that is made up of carbon and oxygen atoms. So, it is concluded that ammonium oxalate is an ionic compound and not a covalent compound since the anion and cation have ionic bonds between them.

4. How does ammonium oxalate act as an anticoagulant?

The oxalates from the ammonium oxalate combine with calcium in the blood and produce an insoluble precipitate. This insoluble precipitate is calcium oxalate. Hence, there is a lower calcium molecule for the formation of coagulation.

5. How do you dispose of ammonium oxalate?

For a Solid ammonium oxalate, it should be collected in a beaker and dissolved in a large amount of water. Soda ash is added and mixed and which is followed by neutralisation with 6M hydrochloric acid and collected in a corrosion-proof container for disposal.

6. What is the odour of ammonium oxalate?

Ammonium oxalate does not have any smell and is non-volatile by nature.

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