Editing CAS Registry Number (section)

== Granularity ==
* [[Stereoisomer]]s and [[racemic mixture]]s are assigned discrete CAS Registry Numbers: {{sc|L}}-[[epinephrine]] has 51-43-4, {{sc|D}}-epinephrine has 150-05-0, and racemic {{sc|DL}}-epinephrine has 329-65-7
* Different [[phase (matter)|phase]]s do not receive different CAS RNs (liquid water and ice both have 7732-18-5), but different crystal structures do ([[carbon]] in general is 7440-44-0, [[graphite]] is 7782-42-5 and [[diamond]] is 7782-40-3)
* Commonly encountered mixtures of known or unknown composition may receive a CAS RN; examples are [[Leishman stain]] (12627-53-1) and [[mustard oil]] (8007-40-7).
* Some [[chemical elements]] are discerned by their oxidation state, e.g. the element [[chromium]] has 7440-47-3, the trivalent Cr(III) has 16065-83-1 and the [[Hexavalent chromium|hexavalent Cr(VI) species]] have 18540-29-9.
* Occasionally whole classes of molecules receive a single CAS RN: the class of enzymes known as [[alcohol dehydrogenase]]s has 9031-72-5.