Citric acid is a weak organic acid that has the chemical formula C6H8O7. 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 chelating agent.
Anhydrous citric acid is a Calculi Dissolution Agent and Anti-coagulant. The mechanism of action of anhydrous citric acid is as an Acidifying Activity and Calcium Chelating Activity. The physiologic effect of anhydrous citric acid is by means of Decreased Coagulation Factor Activity.
Anhydrous Citric Acid is a tricarboxylic acid found in citrus fruits. Citric acid is used as an excipient in pharmaceutical preparations due to its antioxidant properties. It maintains stability of active ingredients and is used as a preservative. It is also used as an acidulant to control pH and acts as an anticoagulant by chelating calcium in blood.
Citric acid was first isolated in 1784 by the chemist Carl Wilhelm Scheele, who crystallized it from lemon juice. It can exist either in an anhydrous (water-free) form or as a monohydrate. The anhydrous form crystallizes from hot water, while the monohydrate forms when citric acid is crystallized from cold water. The monohydrate can be converted to the anhydrous form at about 78 °C. Citric acid also dissolves in absolute (anhydrous) ethanol (76 parts of citric acid per 100 parts of ethanol) at 15 °C. It decomposes with loss of carbon dioxide above about 175 °C.
|Molar mass||192.12 g·mol−1|
|Appearance||crystalline white solid|
|Density||1.665 g/cm3 (anhydrous)|
|Melting point||156 °C (313 °F; 429 K)|
|Boiling point||310 °C (590 °F; 583 K) decomposes from 175 °C|
|Solubility in water||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
|Viscosity||6.5 cP (50% aq. sol.)|