Which chemical is not commonly found in most neutralizers?

The correct choice identifies potassium as the chemical that is not commonly found in most neutralizers used in hair perming and relaxing procedures. Neutralizers are formulated to halt the action of the perming or relaxing agents and to help restore the hair's natural pH balance after the treatment.

Sodium bromate, hydrogen peroxide, and sodium perborate are all commonly used in neutralizers due to their oxidizing properties. These chemicals work by forming cross-links in the hair structure, essential for setting the new shape after a perm or relaxer treatment.

Potassium, while a common element in various hair products, does not play a role in the neutralization process in the same way that the other chemicals do. Thus, its absence from typical neutralizers is why it is the correct answer in this context.