Bromocresol purple

In its cyclic sulfonate ester form, it has a pKa value of 6.3, and is usually prepared as a 0.04% aqueous solution.

Use of BCP in this application may provide some advantage over older methods using bromocresol green.

[6] Bromocresol purple milk solids glucose agar is used as a medium used to distinguish dermatophytes from bacteria and other organisms in cases of ringworm fungus (T. verrucosum) infestation in cattle and other animals.

Changing the level of acidity causes a shift in the equilibrium between two different structures that have different colors.

As the pH decreases, it converts to a sultone (cyclic sulfonic ester) that colors the solution yellow.

Skeletal formula of bromocresol purple in cyclic form
Ball-and-stick model of the bromocresol purple molecule in cyclic form
NFPA 704 four-colored diamond Health 1: Exposure would cause irritation but only minor residual injury. E.g. turpentine Flammability 0: Will not burn. E.g. water Instability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogen Special hazards (white): no code
A sample of bromocresol purple in its violet form