Which of the following items is NOT listed as a chemical precursor under HSC 481.124?

Hydrofluoric acid is not identified as a chemical precursor under HSC 481.124. This statute specifically delineates certain chemicals that are precursors in the synthesis of controlled substances, focusing primarily on those substances that can be used in illegal drug manufacturing processes. Anhydrous ammonia, phenylacetic acid, and ephedrine are among those listed due to their immediate applicability in the production of various illicit drugs. Hydrofluoric acid, while it is a hazardous chemical with industrial applications, does not have a role as a precursor for controlled substances as defined by this particular section of the Health and Safety Code. Thus, it stands apart from the other listed substances in this context.