PARAMETERS

USP

STANDARD

RESULT

REMARKS

Description

Colourless, translucent crystals, or white, granular to fine, crystalline powder.

Melting point

The anhydrous form melts at about 153? with decomposition

Solubility

Very soluble in water; freely soluble in alcohol; very slightly soluble in ether.

Clarity of solution

The test solution shows the same clarity as that of water

Colour of solution

The test solution is not more intensity coloured than the standard solutions A, B, C or water

Identification

<197K>

Infrared absorption

Water?Method I <921>

Not more than 1.0 %

Readily carbonizable substances

The colour of the acid is not darker than that of a similar volume of Matching Fluid K (Color and Achromicity <631>)

Residue on ignition <281>

Not more than 0.1% determined on 1.0 g

Sulfate

Any turbidity produced in the test solution after 5 minutes standing is not greater than that produced in the standard solution ( 0.015%)

Heavy metals <231>

The limit is 0.001%

Limit of oxalic acid

Any pink colour produced in the test solution is not more intense than that produced in the control solution (0.036 %)

Organic volatile impurities Method IV <467>

Meets the requirements

Assay

It contains not less than 99.5% and not more than 100.5% of C₆H₈O₇, calculated on the anhydrous basis