4-(2-Pyridylazo)resorcinol (PAR),

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

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C₁₁H₉N₃O₂ free acid; C₁₁H8N₃NaO₂ monosodium salt 11        215.21,

free acid         237.21,

monosodium salt CAS RN^®: 1141-59-9, free acid; 16593-81-0, monosodium salt. -Use ACS reagent grade.