weak organic acid
Citric acid is a weak organic acid. It can be found in citrus fruits ( like oranges). It is used by organisms for Krebs cycle. It acts like a preservative when added to food. It is also used to add a sour (acidic) taste to foods and soft drinks. In the European Union it is known as E 330, as a food additive.
|Preferred IUPAC name
3D model (JSmol)
|E number||E330 (antioxidants, ...)|
CompTox Dashboard (EPA)
|Molar mass||192.123 g/mol (anhydrous), 210.038 g/mol (monohydrate)|
|Appearance||Crystalline white solid|
|Density||1.665 g/cm3 (anhydrous)|
1.542 g/cm3 (18 °C, monohydrate)
|Melting point||156 °C (313 °F; 429 K)|
|Boiling point||310 °C (590 °F; 583 K) decomposes from 175 °C|
|117.43 g/100 mL (10 °C)|
147.76 g/100 mL (20 °C)
180.89 g/100 mL (30 °C)
220.19 g/100 mL (40 °C)
382.48 g/100 mL (80 °C)
547.79 g/100 mL (100 °C)
|Solubility||soluble in acetone, alcohol, ether, ethyl acetate, DMSO|
insoluble in C
6, CHCl3, CS2, toluene
|Solubility in ethanol||62 g/100 g (25 °C)|
|Solubility in amyl acetate||4.41 g/100 g (25 °C)|
|Solubility in diethyl ether||1.05 g/100 g (25 °C)|
|Solubility in 1,4-Dioxane||35.9 g/100 g (25 °C)|
|Acidity (pKa)||pKa1 = 3.13|
pKa2 = 4.76
pKa3 = 6.39, 6.40
Refractive index (nD)
|1.493–1.509 (20 °C)|
1.46 (150 °C)
|Viscosity||6.5 cP (50% aq. sol.)|
|Std enthalpy of
|Std enthalpy of
−1972.34 kJ/mol (monohydrate)
|Specific heat capacity, C||226.51 J/(mol·K) (26.85 °C)|
|Main hazards||skin and eye irritant|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|verify (what is ?)|
Carl Wilhelm Scheele was the first who could extract citric acid from lemons, in 1782. The substance was probably known to alchemists, perhaps with a different name. The Arabian alchemist Geber is said to have discovered citric acid in the 9th century. Citric Acid contains 6 Carbon atoms, 8 Hydrogen atoms and 7 Oxygen atoms. Its chemical formula is C6H8O7.
- As a water softener
- It is often used in detergents, to avoid the smell of acid, esp. Acetic acid
- As a preserving agent
- Citric acid and its salts prevent blood clotting. Blood donations are kept liquid using citric acid.
- ↑ CID 22230 from PubChem
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 "citric acid". chemister.ru.
- ↑ 3.0 3.1 3.2 3.3 3.4 CID 311 from PubChem
- ↑ "Data for Biochemical Research". ZirChrom Separations, Inc. Retrieved January 11, 2012.
- ↑ "Ionization Constants of Organic Acids". Michigan State University. Retrieved January 11, 2012.
- ↑ 6.0 6.1 6.2 Citric acid in Linstrom, Peter J.; Mallard, William G. (eds.); NIST Chemistry WebBook, NIST Standard Reference Database Number 69, National Institute of Standards and Technology, Gaithersburg (MD), http://webbook.nist.gov (retrieved 2014-06-02)