OlfactionaryThe story everyone repeats
The legend goes like this: in 1920, perfumer Ernest Beaux was preparing sample formulas for Coco Chanel, and either he or a lab assistant accidentally used pure aldehydes instead of a 10-percent dilution, a mistake, bad handwriting, or a miscalculation, depending on which version you read. The overdosed sample became Chanel No. 5, the fragrance that introduced synthetic aldehydes to mainstream perfumery and defined an entire genre.
Why it probably isn't true
Fashion historians who've dug into the story consistently land on the same conclusion: it's unverifiable, and the more they look, the less accidental it seems. Ernest Beaux was already an accomplished, technically sophisticated Russian-trained perfumer by 1920, exactly the kind of chemist who understood aldehyde dosing precisely enough that a catastrophic accidental overdose reads as an unlikely explanation for a decision that took real skill to execute well.
What's actually certain
What's undisputed is the effect: Chanel No. 5 was one of the first fragrances built around a heavy aldehyde overdose deliberately or not, giving it a clean, almost metallic "frozen air" quality that had never been marketed at that scale before, and the formula's success permanently changed what mainstream perfumery was willing to smell like.