tropaeolin
noun
tro·pae·o·lin
variants or tropeolin
trōˈpēələ̇n
plural -s
often capitalized
: any of several orange or orange-yellow azo dyes some of which (as methyl orange) are used as acid-base indicators or as biological stains
Word History
Etymology
International Scientific Vocabulary tropaeol- (from New Latin Tropaeolum) + -in
First Known Use
1878, in the meaning defined above