Meanwhile his father's saltpeter business had been running into difficulties because the product could be manufactured more cheaply in India, and Courtois returned to help his father. Saltpeter was obtained from the seaweed washed ashore in Normandy; the ashes (known as 'varec') were leached for
sodium
and
potassium
salts. Courtois noticed that the
copper
vats in which the lye was stored were becoming corroded by some unknown substance. By chance, in 1811, during the process of extracting the salts, he added excess concentrated
sulfuric
acid to the lye (the solution obtained by leaching) and was astonished to see a vapor of a superb violet colour that condensed on cold surfaces to form brilliant crystalline plates. Courtois suspected that this was a new element but lacked the confidence and the laboratory equipment to establish this and asked Charles Bernard Desormes (1777-1862), the discoverer in 1801 of carbon dioxide, to continue his researches. His discovery was announced in 1813, and Joseph-Louis Gay-Lussac and
Humphry Davy
oon verified that it was an element, Gay-Lussac naming it
iodine
(from the Greek for 'violet'). |