I am wondering what could cause my litmus paper to first react to the alkaline. turning blue, and then changing to an acidic red color?
closed as unclear what you're asking by airhuff, Martin - マーチン♦ Jun 1 '17 at 10:16
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Litmus paper contains a pH indicator, which is a compound that changes color in the presence of acid or base. Natural litmus contains numerous pH-sensitive dyes, but most of them are based on the 7-hydroxyphenoxazone core. In the presence of acid, the imine nitrogen is protonated; in base, the phenolic oxygen is deprotonated. These reactions are reversible, so the color will change when the pH is changed.