Citric acid
[CAS# 77-92-9]

Identification

• Classification: Organic raw materials >> Carboxylic compounds and derivatives >> Acyclic carboxylic acid
• Name: Citric acid
• Synonyms: Citric acid anhydrous; 2-Hydroxy-1,2,3-propanetricarboxylic acid; 2-Hydroxytricarballylic acid
• Molecular Formula: C₆H₈O₇
• Molecular Weight: 192.12
• CAS Registry Number: 77-92-9
• EC Number: 201-069-1
• SMILES: C(C(=O)O)C(CC(=O)O)(C(=O)O)O

Properties

• Solubility: 1 M (water 20 °C)
• Density: 1.665 g/mL (20 °C)
• Melting point: 153-154.5 °C
• Flash point: 174 °C
• Water solubility: 750 g/L (20 °C)

Safety Data

• Hazard Symbols: GHS07 Warning
• Risk Statements: H319--H335
• Safety Statements: P261-P264+P265-P271-P280-P304+P340-P305+P351+P338-P319-P337+P317-P403+P233-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Eye irritation	Eye Irrit.	2	H319
Specific target organ toxicity - single exposure	STOT SE	3	H335
Skin irritation	Skin Irrit.	2	H315
Serious eye damage	Eye Dam.	1	H318
Skin corrosion	Skin Corr.	1B	H314
Eye irritation	Eye Irrit.	2A	H319
Chronic hazardous to the aquatic environment	Aquatic Chronic	3	H412
Reproductive toxicity	Repr.	2	H361

Discovery and Applications

Citric acid is a ubiquitous yet extraordinary compound that has left an indelible mark on numerous industries and everyday applications. Citric acid was first isolated from lemon juice in 1784 by Swedish chemist Carl Wilhelm Scheele. Its name is derived from the Latin word ""citrus,"" reflecting its abundant presence in citrus fruits such as lemons, oranges, and limes. In addition to fruits, citric acid is naturally found in a variety of vegetables and certain fungi, making it readily available and widely used.

Citric acid is a tricarboxylic acid with the molecular formula C6H8O7. It exists as a crystalline powder at room temperature and has a sour taste similar to that of citrus fruits. Citric acid has three carboxylic acid functional groups and is extremely soluble in water, allowing it to be used in a variety of aqueous solutions.

The industrial applications of citric acid are wide and varied. It is primarily used as an acidulant and flavor enhancer in the food and beverage industry. Its ability to impart a sour taste makes it valuable in soft drinks, confectionery, and processed foods. In addition, citric acid's chelating properties can be used for food preservation and color and flavor stabilization.

In addition to food, citric acid plays a key role in the pharmaceutical and cosmetic industries. It can be used as a pH adjuster in drug formulations to ensure the stability and bioavailability of active ingredients. In cosmetics, it can be used as a natural preservative and pH balancer in skin care products, demonstrating its versatility and safety.

In biomedical research, the role of citric acid extends to the development of medical devices and drug delivery systems. Its biocompatibility and ability to enhance solubility make it ideal for formulating parenteral solutions and as a component of hemodialysis solutions. In addition, citric acid's antimicrobial properties contribute to its use as a household cleaner and disinfectant, promoting environmental sustainability and safety.

Despite the many benefits of citric acid, challenges such as price fluctuations due to fluctuations in raw material costs and the need for effective waste management in production remain. Future research aims to optimize citric acid production technology, enhance its functional properties, and explore new applications in emerging fields such as bioplastics and renewable energy.

References

2025. 3D nanofiber sponge based on natural insect quaternized chitosan/pullulan/citric acid for accelerating wound healing. Carbohydrate Polymers, 346.
DOI: 10.1016/j.carbpol.2024.122827

2025. Physiological iron chelators pyrophosphate and citrate have different effects on the proportions of monoferric transferrin metalloforms. Journal of Inorganic Biochemistry, 263.
DOI: 10.1016/j.jinorgbio.2024.112773

2025. Eco-friendly hydrotropic spectrophotometric analysis of ranolazine hydrochloride. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 326.
DOI: 10.1016/j.saa.2024.125122