Pierre Louis Dulong, a French naturalist, born in Rouen, Feb. 12, 1785, died in Paris, July 19, 1838. He studied medicine, which he practised for some time, and then devoted himself to physical science. After numerous analyses and researches upon chlorine and ammonia, he was led in 1811 to the discovery of the chloride of nitrogen. He was twice injured by the explosions of this new compound, and lost an eye and a finger. In 1816 he discovered hypophosphorous acid, and introduced into the nomenclature the prefix hypo, to denote a less degree of oxidation. In 1820 he labored with Berzelius in the laboratory of Berthollet, and investigated the origin of animal heat. He found that in the carnivora the heat due to the transformation of oxygen into carbonic acid is not more than one half of the whole, and in the herbivora even a smaller proportion. In 1825 he was appointed on the commission to provide precautions against the explosion of steam boilers; and for four years he labored almost alone with Arago in determining the elastic force of steam at different temperatures. Dulong was a member of the academy of sciences, and in 1832 succeeded Cuvier as perpetual secretary for the department of physical sciences.

His numerous works treat particularly of gases and heat.