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C6H12N4 140.19


Hexamethylenetetramine [100-97-0].
» Methenamine, dried over phosphorus pentoxide for 4 hours, contains not less than 99.0 percent and not more than 100.5 percent of C6H12N4.
Packaging and storage— Preserve in well-closed containers.
B: Heat a solution (1 in 10) with 2 N sulfuric acid: formaldehyde is liberated, recognizable by its odor and by its darkening of paper moistened with silver ammonium nitrate TS. On the subsequent addition of an excess of 1 N sodium hydroxide to the solution, ammonia is evolved.
Loss on drying 731 Dry it over phosphorus pentoxide for 4 hours: it loses not more than 2.0% of its weight.
Residue on ignition 281: not more than 0.1%.
Chloride 221 A 1.0-g portion shows no more chloride than corresponds to 0.20 mL of 0.020 N hydrochloric acid (0.014%).
Sulfate— To 10 mL of a solution (1 in 50), acidified with 5 drops of hydrochloric acid, add 5 drops of barium chloride TS: no turbidity is produced within 1 minute.
Ammonium salts— To 10 mL of a solution (1 in 20) add 1 mL of alkaline mercuric-potassium iodide TS: the mixture is not darker in color than a mixture of 1 mL of the reagent and 10 mL of water.
Heavy metals, Method I 231 Dissolve 2 g in 10 mL of water, add 2 mL of 3 N hydrochloric acid, and dilute with water to 25 mL. Proceed as directed, except to use glacial acetic acid to adjust the pH: the limit is 0.001%.
Chromotropic acid spot test solution— Suspend 100 mg of chromotropic acid in 2 mL of water, and cautiously add 3 mL of sulfuric acid. Allow to cool. Add 25 mL of sulfuric acid, and mix. [note—If excessive heat generated during mixing causes a violet color to appear in the solution, discard the solution and prepare another, taking precautions to avoid excessive heat.]
Procedure— Transfer about 1 g of Methenamine, previously dried and accurately weighed, to a beaker. Add 40.0 mL of 1 N sulfuric acid VS, and heat to a gentle boil, adding water from time to time if necessary, until the formaldehyde has been expelled. Test for the absence of formaldehyde by adding a drop of the assay solution to a glass fiber filter disk, on a watch glass, on which has previously been placed 3 or 4 drops of Chromotropic acid spot test solution. Formaldehyde produces a violet color with this reagent; repeat the test until no violet color is obtained on the warmed test filter disk upon comparison with a blank filter disk to which no assay specimen is added. Cool, add 20 mL of water, then add methyl red TS, and titrate the excess acid with 1 N sodium hydroxide VS. Perform a blank determination (see Residual Titrations under Titrimetry 541). Each mL of 1 N sulfuric acid is equivalent to 35.05 mg of C6H12N4.
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Behnam Davani, Ph.D., M.B.A.
Senior Scientist
(MDAA05) Monograph Development-Antivirals and Antimicrobials
Reference Standards Lili Wang, Technical Services Scientist
USP32–NF27 Page 2920
Chromatographic Column—
Chromatographic columns text is not derived from, and not part of, USP 32 or NF 27.