Definition: a solution prepared by adding a 2% solution of phenol in water to aqueous ferric chloride until the solution becomes violet; this turns lemon yellow in the presence of lactic acid, assumes an opaline tint in butyric acid, and is decolorized by hydrochloric acid.
[J. A. C. Uffelmann]
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Examples: glitazone, GI cocktail, etc.