hemochromogen
noun
he·mo·chro·mo·gen
variants:
or chiefly British haemochromogen \ ˌhē-mō-ˈkrō-mə-ˌjen, -jən 
\
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Medical Definition of hemochromogen
: a colored compound formed from or related to hemoglobin
especially
: a bright red combination of a nitrogen base (as globin or pyridine) with heme — compare hemoprotein