helianthin

from The Century Dictionary.

• noun A coal-tar color used in dyeing. It is the ammonia salt of dimethyl-aniline-azobenzene-sulphonic acid. It produces a fiery orange on silk and wool. Also called gold orange.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Chem.) An artificial, orange dyestuff, analogous to tropaolin, and like it used as an indicator in alkalimetry; -- called also methyl orange.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun methyl orange