3. If, as indicated in paragraph 2 of Annex III to the Directive, a substance is identified in Part I of this Schedule as an “. . . acid, salt” and has salts of one or more of the following names (that is to say, salts of aluminium, ammonium, calcium, iron, magnesium, potassium, sodium or zinc), then the free acid corresponding to that substance is not treated as included in the specification of that substance.