The Collaborative International Dictionary
Helianthin
Helianthin \He`li*an"thin\, n. [Prob. fr. L. helianthes, or NL. helianthus, sunflower, in allusion to its color.] (Chem.) An artificial, orange dyestuff, analogous to tropaolin, and like it used as an indicator in alkalimetry; -- called also methyl orange.
Wiktionary
helianthin
n. methyl orange