apans · noun1
See the etymology of the corresponding lemma form.
apans · noun2
From arsonic + phenyl + azo- + naphthalene + sulfonic, from disodium salt of 4-[(2-arsonophenyl)azo]-3-hydroxy-2,7-naphthalenedisulfonic acid.
Etymology from Wiktionary, CC BY-SA 4.0.