PerfumersWorld: Citric acid cyrystals are almost odourless with a sharp lemon-fruity-sour taste. used as a chelating agent to remove fe (iron) from oils and compounds. fe contamination comes from storage in steel drums or during distillation causing severe darkening of the oil. oils commonly affected by fe contamination patchouli clove cinnamon vetiver lemongrass litsea cubeba lemon orange grapefruit. add a pinch (or <1%) of citric acid to a material and wait 7-14 days to see if it lightens. the crystals precipitate so just pour off (decant) the oil from the top or filter the crystals out through a course filter paper.