Congo red paper

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Description

A acid-base indicating paper. Congo red paper is made by impregnating filter paper with a 0.1% aqueous solution of Congo red dye. Congo red is red above pH 5 and blue below pH 3. It is only sensitive to strong acids (mineral acids) and not weak acids (organic acids).

Synonyms and Related Terms

Congo blue paper; Riegel's paper; Herzberg's paper