Claude Berthollet was a French theoretical chemist, born at Talloire, a village of Savoy, who played an important role in the birth of modern chemistry. Berthollet studied at Turin, and afterwards went to Paris; in 1781 he was elected a member of the Academy of Sciences. In 1785 he announced his support for the antiphlogistic doctrines (see phlogiston) of Antoine Lavoisier, whom he aided both in his researches on gunpowder and in the formation of a new chemical nomenclature. In the same year, Berthollet published a paper on "dephlogisticated marine air" – now called chlorine – pointing out its use for bleaching purposes; and following up the experiments of Joseph Priestley, he showed ammonia to be a compound of three volumes of hydrogen gas and one volume of nitrogen gas.

During the early part of the French Revolution, Berthollet traveled through the country, giving instruction as to the process of smelting and converting iron into steel. He was made a senator by Napoleon Bonaparte, who also made him a count. Notwithstanding, he voted for the deposition of Bonaparte in 1814; and on the restoration of the Bourbons he was created a peer.