Definition

Chemical name

Citric acid

2-Hydroxy-1,2,3-propanetricarboxylic acid

β-Hydroxytricarballytic acid

Einecs

201-069-1

Chemical formula

1. (a)

   C₆H₈O₇ (anhydrous)

1. (b)

   C₆H₈O₇·H₂O (monohydrate)

Molecular weight

1. (a)

   192,13 (anhydrous)

1. (b)

   210,15 (monohydrate)

Assay

Citric acid may be anhydrous or it may contain 1 molecule of water. Citric acid contains not less than 99,5 % of C₆H₈O₇, calculated on the anhydrous basis

Description

Citric acid is a white or colourless, odourless, crystalline solid, having a strongly acid taste. The monohydrate effloresces in dry air

Identification

Very soluble in water; freely soluble in ethanol; soluble in ether

Purity

Water content

Anhydrous citric acid contains not more than 0,5 % water; citric acid monohydrate contains not more than 8,8 % water (Karl Fischer method)

Sulphated ash

Not more than 0,05 % after calcination at 800 ± 25 ^oC

Arsenic

Not more than 1 mg/kg

Lead

Not more than 1 mg/kg

Mercury

Not more than 1 mg/kg

Heavy metals (as Pb)

Not more than 5 mg/kg

Oxalates

Not more than 100 mg/kg, expressed as oxalic acid, after drying

Readily carbonisable substances

Heat 1 g of powdered sample with 10 ml of 98 % minimum sulphuric acid in a water bath at 90 ^oC in the dark for one hour. Not more than a pale brown colour should be produced (Matching Fluid K)