Ichthammol Ointment
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This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition
Issued and maintained by the United States Pharmacopeial Convention (USP)
1 DEFINITION
Ichthammol Ointment contains an amount of ichthammol equivalent to NLT 0.25% of ammonia (NH₃).
Ichthammol: 100 g
Lanolin: 100 g
Petrolatum: 800 g
To make: 1000 g
Thoroughly incorporate the Ichthammol with the Lanolin, and combine this mixture with the Petrolatum.
2 ASSAY
Ammonia
Sample:
Transfer a portion of the Ointment, equivalent to 2 g of ichthammol, to a 250-mL beaker, and add 70 mL of boiling water. Mix with a glass rod, and heat on a steam bath with frequent agitation for 10 min. Cover with a watch glass without removing the stirring rod, and allow to stand at room temperature for 15–20 min. Place in a refrigerator to cause the upper layer to congeal, form a second opening through the congealed layer with the glass rod, and transfer the dark-colored aqueous extract to a funnel containing a pledget of cotton, collecting the ltrate in a 500-mL volumetric ask. Repeat the extraction of the portion of the Ointment several times in the same manner until the aqueous extract is practically colorless, passing each extract through the same cotton lter into the ask containing the main extract. Dilute with water to volume, and mix.
Titrimetric system
Mode: Residual titration
Titrant: 0.05 N sulfuric acid VS
Back-titrant: 0.05 N sodium hydroxide VS
Endpoint detection: Colorimetric
Analysis:
Transfer 100.0 mL of the Sample to a suitable distillation ask, add 3 g of paran, and add 20 mL of sodium hydroxide solution (4 in 10). Connect the ask to a condenser by means of a spray trap, and immerse the lower outlet tube of the condenser in 30.0 mL of Titrant. Distill slowly, collect about 50 mL of distillate, and then titrate the excess sulfuric acid with Back-titrant, using methyl red TS as the indicator. Perform a blank determination, and make any necessary correction.
Each mL of Titrant is equivalent to 0.8515 mg of ammonia (NH₃).
Acceptance criteria:
NLT 0.25% of ammonia (NH₃)
3 ADDITIONAL REQUIREMENTS
Packaging and Storage:
Package in collapsible tubes or in tight containers. Avoid prolonged exposure to temperatures exceeding 30°.
