Citric Acid vs. Oxalic Acid

What's the Difference?

Citric acid and oxalic acid are both organic acids commonly found in nature. However, they differ in their chemical structures and properties. Citric acid, found in citrus fruits, has a tricarboxylic acid structure and is a weak acid. It is widely used as a food additive, flavor enhancer, and cleaning agent. On the other hand, oxalic acid, found in many plants, has a dicarboxylic acid structure and is a stronger acid. It is commonly used as a cleaning agent, rust remover, and in some industrial processes. While both acids have their own unique uses, citric acid is generally considered safer for consumption due to its lower toxicity compared to oxalic acid.


AttributeCitric AcidOxalic Acid
SolubilityHighly soluble in waterSoluble in water
Chemical FormulaC6H8O7C2H2O4
AppearanceColorless crystals or white powderColorless crystals or white powder
OccurrenceFound in citrus fruitsFound in many plants, including rhubarb and spinach
UsesFood and beverage additive, cleaning agent, pH adjusterWood bleach, rust remover, cleaning agent
ToxicityGenerally recognized as safe (GRAS) by FDAPoisonous if ingested in large quantities

Further Detail


Citric acid and oxalic acid are two organic acids that are commonly found in nature and have various applications in different industries. While both acids share some similarities, they also have distinct attributes that set them apart. In this article, we will explore the characteristics of citric acid and oxalic acid, their chemical properties, uses, and potential health effects.

Chemical Properties

Citric acid, with the chemical formula C6H8O7, is a weak organic acid that occurs naturally in citrus fruits such as lemons, oranges, and grapefruits. It is a white crystalline powder with a sour taste and is highly soluble in water. On the other hand, oxalic acid, with the chemical formula C2H2O4, is also a white crystalline solid but has a more acidic taste compared to citric acid. It is soluble in water and forms colorless crystals.


Citric acid is primarily found in citrus fruits and some berries. It is produced commercially through the fermentation process of sugar by certain strains of mold. Oxalic acid, on the other hand, is found in various plants, including rhubarb, spinach, and sorrel. It can also be synthesized through the oxidation of carbohydrates or by treating sodium formate with nitric acid.


Citric acid has a wide range of applications in the food and beverage industry. It is commonly used as a natural preservative, flavor enhancer, and acidulant in soft drinks, candies, jams, and other processed foods. It is also used in the production of effervescent tablets and as a cleaning agent due to its ability to remove limescale and rust. Additionally, citric acid is utilized in the pharmaceutical industry for its antioxidant properties and as a chelating agent in certain medications.

Oxalic acid, on the other hand, has diverse uses in various industries. In the textile industry, it is used as a bleaching agent for fabrics and fibers. It is also employed in the production of dyes and ink. In the metal cleaning and polishing industry, oxalic acid is used to remove rust and stains from metals. Furthermore, it finds applications in the synthesis of various chemicals, such as pharmaceuticals, as well as in the preparation of wood stains and varnishes.

Health Effects

When consumed in moderate amounts, citric acid is generally recognized as safe by regulatory authorities such as the U.S. Food and Drug Administration (FDA). It is naturally present in many fruits and is an essential component of the human diet. However, excessive consumption of citric acid may lead to dental erosion and can exacerbate symptoms in individuals with gastroesophageal reflux disease (GERD) due to its acidic nature.

Oxalic acid, on the other hand, can be toxic when ingested in large quantities. It can form insoluble crystals called calcium oxalate, which can lead to the formation of kidney stones. Individuals with a history of kidney problems or those prone to kidney stone formation should avoid consuming foods high in oxalic acid. However, it is important to note that oxalic acid is present in many common foods, and its consumption in moderate amounts is generally considered safe for most individuals.


In conclusion, citric acid and oxalic acid are two organic acids with distinct characteristics and applications. Citric acid is commonly found in citrus fruits and is widely used in the food and beverage industry as a preservative and flavor enhancer. It also has applications in cleaning agents and pharmaceuticals. Oxalic acid, on the other hand, is found in various plants and has uses in industries such as textiles, metal cleaning, and chemical synthesis. While citric acid is generally safe for consumption, excessive intake of oxalic acid can have adverse health effects. It is important to consider the source, chemical properties, and potential health implications when using these acids in various applications.

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