Pierre Louis Dulong FRS FRSE (; ; 12 February 1785 – 19 July 1838) was a French physicist and chemist. He is remembered today largely for the law of Dulong and Petit, although he was much-lauded by his contemporaries for his studies into the elasticity of steam, conduction of heat, and specific heats of gases. He worked most extensively on the specific heat capacity and the expansion and refractive indices of gases. His collaboration with Alexis Thérèse Petit led to the discovery of the Dulong–Petit law on heat capacity.
Early life and education
Dulong was born in Rouen, France.
An only child, he was orphaned at the age of 4, he was brought up by his aunt in Auxerre. He gained his secondary education in Auxerre and the Lycée Pierre Corneille in Rouen before entering the École polytechnique, Paris in 1801, only for his studies to be impeded by poor health. He began studying medicine, but gave this up, possibly because of a lack of financial means, The fact that Dulong kept the accident a secret meant that Humphry Davy's investigation of the compound had the same unfortunate consequence, although Davy's injuries were less severe.
In addition to his accomplishments in chemistry, Dulong has been hailed as an interdisciplinary expert. His contemporaries in the Royal Society of London acknowledged his "command of almost every department of physical science".
In 1815, Dulong collaborated for the first time with Alexis Thérèse Petit, in publishing a paper on heat expansion. The two would continue to collaborate, researching the specific heats of metals. In 1819, Dulong and Petit showed that the mass heat capacity of metallic elements are inversely proportional to their atomic masses, this being now known as the Dulong–Petit law. For this discovery Dulong was honored by the French Academy in 1818. This law helped develop the periodic table and, more broadly, the examination of atomic masses. He made the first precise comparison of the mercury- and air-temperature scales. In 1830, he was elected a foreign member of the Royal Swedish Academy of Sciences.
He died of stomach cancer in Paris. At the time of his death, he was working on the development of precise methods in calorimetry. His last paper, published the year of his death, examined the heat released from chemical reactions.
Dulong was noted both for his devotion to science and the stolid, almost casual, bravery he displayed in prosecuting his experiments. One such experiment involved the construction of a glass tubular apparatus atop the tower at the Abbey of Saint Genevieve. The tower was unsteady enough that an explosion of the experimental materials, considerably likely considering their volatility, could easily have toppled the tower and killed the researching physicists, including Dulong. The experiment though "full of danger and difficulty", was completed under Dulong's leadership.
Another example of Dulong's indifference to danger amid scientific pursuit came about in his studies into nitrogen trichloride. Despite losing two fingers and one eye in his initial experiments, Dulong continued to research the unknown substance. His inquiry led to more injuries, after which he turned over the results of his studies to Humphry Davy.
Burial and honors
In life, Dulong poured the bulk of his finances into his scientific experiments. He was often destitute. As a result, he died without leaving his family any significant inheritance.