Citric acid

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Citric acid
Zitronensäure - Citric acid.svg
IUPAC name 2-hydroxypropane-1,2,3-tricarboxylic acid
Other names 3-carboxy-3-hydroxypentanedioic acid
CAS number 77-92-9
PubChem 311
DrugBank DB04272
KEGG D00037
Molecular formula C6H8O7
Molar mass 192.124 g/mol (anhydrous)
210.14 g/mol (monohydrate)
Appearance crystalline white solid
Density 1.665 g/cm3(1.5g/cm3 for monohydrate)
Melting point

153 °C, 426 K, 307 °F

Boiling point

175 °C, 448 K, 347 °F (decomposes)

Solubility in water 73 g/100 ml (20 °C)
Acidity (pKa) pKa1 = 3.09
pKa2 = 4.75
pKa3 = 5.41 [1]
Main hazards skin and eye irritant
Related compounds
Related compounds sodium citrate, calcium citrate
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Citric acid crystals, magnified about 200 times, seen through a polarizing filter.

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.

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.

Main uses[change | change source]

References[change | change source]

  1. Dawson, R. M. C.; et al. (1959). Data for Biochemical Research. Oxford: Clarendon Press.

Other websites[change | change source]