I require Congo red indicator for an experiment I wish to perform involving dipping a cellulose sponge into an acid and a base. I first want to dye the cellulose sponge with Congo red, and observe the color change of the sponge as I place it in acids and bases.
Congo red apparently binds to cellulose and thus is suitable for this experiment. Unfortunately the laboratory doesn't have this indicator at the moment. Are there any other indicators that could be used for this effect instead?