C4H4O4 -- 116.1 -- 110-16-7
DEFINITION
Maleic acid contains not less than 99.0 per cent and not more than the equivalent of
101.0 per cent of (Z)-butenedioic acid, calculated with reference to the anhydrous
substance.
CHARACTERS
A white, crystalline powder, freely soluble in water and in alcohol.
IDENTIFICATION
A. Dilute 5 ml of solution S (see Tests) to 10 ml with water. The pH of the dilution is
less than 2.
B. Examine the chromatograms obtained in the test for fumaric acid. The principal spot
in the chromatogram obtained with test solution (b) is similar in position and size to
the principal spot in the chromatogram obtained with reference solution (a).
C. Dissolve 0.1 g in 10 ml of water (solution a). To 0.3 ml of solution (a) add a
solution of 10 mg of resorcinol in 3 ml of sulphuric acid. Heat on a water-bath for 15
minUTES; no colour develops. To 3 ml of solution (a) add 1 ml of bromine water. Heat on
a water-bath to remove the bromine (15 min), heat to boiling and cool. To 0.2 ml of this
solution add a solution of 10 mg of resorcinol in 3 ml of sulphuric acid. Heat on a
water-bath for 15 min. A violet-pink colour develops.
TESTS
Solution S
Dissolve 5.0 g in water R and dilute to 50 ml with the same solvent.
Appearance of solution
Solution S is clear and not more intensely colored than reference solution.
Fumaric acid
To pass the test
Iron
To 10 ml of solution S add 2 ml of dilute hydrochloric acid and 0.05 ml of bromine
water. After 5 min, remove the excess of bromine by passing a current of air and add 3
ml of potassium thiocyanate solution. Shake. Prepare a standard at the same time and in
the same manner, using a mixture of 5 ml of iron standard solution (1 ppm Fe) R, 1 ml of
dilute hydrochloric acid, 6 ml of water and 0.05 ml of bromine water. Allow both
solutions to stand for 5 min. Any red colour in the test solution is not more intense
than that in the standard (5 ppm).
Heavy metals
1.0 g complies with limit test D for heavy metals (10 ppm).
Water
Not more than 2.0 per cent, determined on 1.00 g by the semi-micro determination of
water.
Sulphated ash
Not more than 0.1 per cent, determined on 1.0 g.
Maleic Acid
C4H4O4 116.07
(Z)-Butenedioic acid
Cis-Butenedioic acid [CAS 110-16-7].
Maleic Acid contains not less than 99.0 percent and not more than 101.0 percent of
C4H4O4, calculated on the anhydrous basis.
Identification—
A: Dissolve about 500 mg of Maleic Acid in 10 mL of water: the pH of the solution is
less than 2.
B: To pass chromatography test
C: Dissolve about 35 mg of resorcinol in 10 mL of sulfuric acid (Resorcinol solution).
Dissolve about 100 mg of Maleic Acid in 10 mL of water (Test solution). To 0.3 mL of the
Test solution add 3 mL of the Resorcinol solution, and heat in a water bath for 15
minutes: no color develops. To 3 mL of the Test solution add 1 mL of bromine TS, heat in
a water bath for 15 minutes to remove the bromine, then heat to boiling, and cool. To
0.2 mL of this solution, add 3 mL of the Resorcinol solution, and heat in a water bath
for 15 minutes: a violet-pink color develops.
Color and clarity of solution—
Dilute hydrochloric acid solution— Mix 27.5 mL of hydrochloric acid with
sufficient water to make 1000 mL.
Reference solution— Mix 2.4 mL of ferric chloride CS and 0.6 mL of cobaltous
chloride CS with Dilute hydrochloric acid solution to make 10 mL. Dilute 5 mL of this
solution with Dilute hydrochloric acid solution to make 100 mL.
Test solution— Dissolve about 5 g of Maleic Acid in 50 mL of water.
Procedure— Place the Reference solution and the Test solution in matched
color-comparison tubes, and compare the solutions by viewing them downward against a
white surface : the Test solution is clear and not more intensely colored than the
Reference solution.
Water: not more than 2.0% is found.
Residue on ignition: not more than 0.1%, determined on a 1.0-g portion.
Heavy metals— not more than 10 µg per g.
Limit of fumaric acid— To pass the test
Limit of iron—: not more than 5 µg per g.
