Phenyl Isocyanate
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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)
C6H5NCO 119.12 CAS RN: 103-71-9.-Clear, colorless to straw-yellow liquid of medium volatility. [CAUTION-Phenyl Isocyanate is a violent lacrimator, and the vapor is highly toxic. Handle with care.]
Assay: Transfer 250 mg, accurately weighed, to a glass-stoppered, 250-mL flask. Exercise care to avoid loss by volatilization, and avoid breathing the vapor. Add 20 mL of butylamine solution (25 g of butylamine diluted to 1000 mL with dioxane previously dried over potassium hydroxide pellets), insert the stopper in the flask, and allow to stand for 15 minutes. Add a few drops of methyl red TS and 25 mL of water, and titrate the excess amine with 0.1 N sulfuric acid VS. Perform a blank titration on 20 mL of the butylamine solution (see Titrimetry (541) (CN 1-Aug-2024)). Subtract the volume of 0.1 N sulfuric acid consumed in the test specimen titration from that consumed in the blank titration. Each mL of 0.1 N sulfuric acid, representing this difference, is equivalent to 11.91 mg of C6H5NCO: not less than 97.0% of C6H5NCO is found.
