If you have a pH indicator that\'s water solube, such as Anthocyanin (from Red C

Question

If you have a pH indicator that's water solube, such as Anthocyanin (from Red Cabbage) in a solution, that let' say is pH 7.....so it turns purple. If you make that same solution more acidic, will the pH indicator continue to change color? Or will it stay fixed? I'm trying to find a water-soluble indicator that can stay "fixed" after initial exposure to a solution.

I'm curious because the pH indicator strips seem to be "fixed" after you expose them to a solution, so I'm wondering how that works that it stays that color. I'm curious how a pH indicator would hypothetically act as it travels through the body.

Explanation / Answer

In general, each indicator has a range over which it shows particular, beyond that range the color is not shown.

So the

Anthocyanins can be used as pH indicators because their color changes with pH; they are pink in acidic solutions (pH < 7), purple in neutral solutions (pH ~ 7), greenish-yellow in alkaline solutions (pH > 7), and colourless in very alkaline solutions, where the pigment is completely reduced.[5]

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