Citric Acid

« Back to Glossary Index

Refer to Related Articles

Citric Acid (Wikipedia)
"E330" redirects here. For the locomotive, see FS Class E330.
Citric acid
Zitronensäure - Citric acid.svg
IUPAC name
3-carboxy-3-hydroxypentane-1,5-dioic acid
Other names
Citric Acid
3-carboxy-3-hydroxypentanedioic acid
2-hydroxy-1,2,3-propanetricarboxylic acid
77-92-9 YesY
ChEBI CHEBI:30769 YesY
ChemSpider 305 YesY
DrugBank DB04272 YesY
EC Number 201-069-1
Jmol 3D image Interactive graph
KEGG D00037 YesY
PubChem 22230 (monohydrate) 311, 22230 (monohydrate)
RTECS number GE7350000
Molar mass 192.12 g·mol−1
Appearance crystalline white solid
Odor odorless
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 alcohol, ether, ethyl acetate, DMSO
insoluble in C6H6, 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)
log P -1.64
Acidity (pKa) pKa1 = 3.13
pKa2 = 4.76
pKa3 = 6.39, 6.40
1.493 - 1.509 (20 °C)
1.46 (150 °C)
Viscosity 6.5 cP (50% aq. sol.)
226.51 J/mol·K (26.85 °C)
252.1 J/mol·K
-1548.8 kJ/mol
-1960.6 kJ/mol
-1972.34 kJ/mol (monohydrate)
A09AB04 (WHO)
Main hazards skin and eye irritant
Safety data sheet HMDB
GHS pictograms The exclamation-mark pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)
GHS signal word Warning
Irritant Xi Corrosive C
R-phrases R34, R36/37/38, R41
S-phrases S24/25, S26, S36/37/39, S45
NFPA 704
Flammability code 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g., canola oilHealth code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g., chloroformReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogenSpecial hazards (white): no codeNFPA 704 four-colored diamond
Flash point 155 °C (311 °F; 428 K)
345 °C (653 °F; 618 K)
Explosive limits 8%
Lethal dose or concentration (LD, LC):
3000 mg/kg (rats, oral)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YesYN ?)
Infobox references

Citric acid is a weak organic tribasic acid. It occurs naturally in citrus fruits. In biochemistry, it is an intermediate in the citric acid cycle, which occurs in the metabolism of all aerobic organisms.

More than a million tons of citric acid are manufactured every year. It is used widely as an acidifier, as a flavoring, and as a chelating agent.

A citrate is a derivative of citric acid; that is, the salts, esters, and the polyatomic anion found in solution. An example of the former, a salt is trisodium citrate; an ester is triethyl citrate. When part of a salt, the formula of the citrate ion is written as C6H5O73− or C3H5O(COO)33−.

« Back to Glossary Index