Sweet orange essential oil

Freshly peeled orange: bright, sweet, juicy, without a bitter edge. It fades fast, usually in under half an hour on a smelling strip.

More than nine-tenths of the bottle is limonene, yet limonene contributes almost nothing to the smell of orange. The “orange” comes from a few aldehydes that make up less than one percent, because the nose picks them up at concentrations hundreds of times lower than limonene.

This is the easiest example of the principle the whole Lab rests on: the most abundant compound is not necessarily the one you smell. Two orange oils that are both 95 % limonene can still be clearly different.