[nahy-gruh-seen, -sin] 
| any of the class of deep blue or black dyes obtained by the oxidation of aniline, used as coloring agents in inks and shoe polishes and for dyeing leather, wood, textiles, and furs. |
nigrosine (nī'grə-sēn', -sĭn) or ni·gro·sin (-sĭn)
n.
Any of a class of aniline dyes that vary from blue to black and are used as stains for nervous tissue and as a negative stain for bacteria and spirochetes.
grəˌsin