Bernard Courtois Biography

Bernard Courtois was born in Dijon, France. Exposed to chemistry at an early age, he divided his time between the saltpeter (potassium nitrate) works of his father, Jean- Baptiste Courtois, and the laboratory at the Dijon Academy. In 1791, he became an apprentice for three years to a pharmacist at Auxerre. Courtois was admitted to the famous engineering school in Paris, the École Polytechnique, where he studied under the chemist Antoine François, Comte de Fourcroy.

In 1799, Courtois was drafted in the French military and served as a pharmacist. He then became assistant to chemist Louis Jacques Thénard (1801) and assistant to chemist Armand Seguin (1804). Courtois returned to Dijon to take over his father's business. In 1808, he married a young, nearly-illiterate peasant girl, Madeleine Eulalie Morand.

During the Napoleonic Wars, the British naval blockade cut off foreign imports of saltpeter needed to prepare gunpowder. Courtois used seaweed ash from algae found in Normandy and Britanny as a source of valuable potassium and sodium salts. Because the mother liquor obtained by leaching the ash with water contained undesirable impurities, he removed these by treatment with sulfuric acid. In late 1811 Courtois apparently used too much acid and observed clouds of violet vapor, which had an irritating odor similar to that of chlorine and condensed on cold surfaces, to form dark, almost black, lustrous crystals with a metallic sheen. He had accidentally produced iodine by oxidizing the sodium and potassium iodides in the mother liquor. Suspecting that the new substance was a previously unknown element, Courtois spent approximately six months investigating it but was unable to conduct a thorough study in his primitive laboratory. Lacking the financial resources to continue the research and barely able to support his family by the saltpeter business, he abandoned his work on the substance.

In July 1812, Courtois informed two chemist friends, Charles Bernard Desormes and Nicolas Clément, of his discovery and allowed them to report it to the Institut de France, which they did on November 9, 1813. Upon his request, Desormes and Clémenty continued his research at the laboratory of the Conservatoire des Arts et Métiers. Clément extensively studied the new substance and concluded that it was an element similar to chlorine. That same year, French chemist Joseph Louis Gay- Lussac called the substance "iode" from the Greek word for violet, and English chemist Sir Humphry Davy confirmed its elementary nature. Their results convinced skeptics that chlorine was an element, for if iodine was an element, the chemically-similar chlorine probably was as well. In 1826, Antoine Jérôme Balard confirmed the elementary nature of both iodine and chlorine by discovering a third halogen element, bromine.

During the 1820s Courtois abandoned his saltpeter business and began manufacturing iodine compounds and other chemicals, but this business likewise failed to prosper, and he abandoned it in 1835. Courtois was acknowledged as the discoverer of iodine, which was widely used in the treatment of goiter, and in 1831 the Dijon Academy awarded him the Montyon prize of 6,000 francs "for having improved the art of healing."

Courtois died in Paris on September 27, 1838, without ever having published a scientific paper during his lifetime. On November 9, 1913, the centenary of Desormes and Clément's announcement of his discovery of iodine, a ceremony was held in honor of Courtois' achievements at the Dijon Academy, and a commemorative plaque was placed on the house in which he was born. In 1914 a street in Dijon was named after him.