The FCC (Food Chemicals Codex) method for Substances Darkened by Sulfuric Acid in Ethanol is a qualitative test used to detect oxidizable or reactive organic impurities in ethanol that may cause discoloration when exposed to concentrated sulfuric acid (H₂SO₄). These substances, if present, can affect the odor, color, and stability of ethanol, especially in food, beverage, or pharmaceutical applications.