Phenol Red
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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)
[4,4′-(3H-2,1-Benzoxathiol-3-ylidene)diphenol, S,S-Dioxide], C19H14O5S—354.38—Crystalline powder, varying in color from bright to dark red. Very slightly soluble in water; freely soluble in solutions of alkali carbonates and hydroxides; slightly soluble in alcohol. Transition interval: from pH 6.8 to 8.2. Color change: from yellow to red
