Claude-Louis Berthollet, chemist, c 1810.
© Science Museum / Science & Society Picture Library
Engraving by Ambroise Tardieu. Comte Berthollet (1748-1822) was a French chemist who was elected to the Academy of Sciences in 1781. He helped Antoine Lavoisier research gunpowder and form the new chemical nomenclature. In 1785 he demonstrated the effectivenes of using chlorine for bleaching. He showed ammonia to be a compound of hydrogen and nitrogen. Napoleon made him a count and senator, but Berthollet later voted for his deposition and became a peer after the Bourbon restoration.