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}.
[1913 Webster]