Historedia
Episode 1 of 4

Discovery from Seaweed Ash

When
1811
Where
Normandy and Brittany shores
Part of
Bernard Courtois discovers iodine

Courtois discovered iodine in late 1811 by adding sulfuric acid to seaweed ash while producing saltpetre.

By 1811, the Napoleonic Wars caused a shortage of wood ashes for saltpetre production. Courtois derived potassium nitrate from seaweed abundant on Normandy and Brittany shores. While isolating sodium and potassium compounds from seaweed ash, he added sulfuric acid and discovered iodine.

Sources

  1. Bernard Courtois Wikipedia, revision of 2026-07-21
  2. Iodine Wikipedia, revision of 2026-10-01

Machine-drafted from the cited Wikipedia passages and checked by a reviewing model, not by a human editor. Every passage cites the revision it was written from; dates and places follow those passages.