Pierre Louis Dulong

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Pierre Louis Dulong
Pierre Louis Dulong.jpg
Born(1785-02-12)12 February 1785
Rouen, France
Died19 July 1838(1838-07-19) (aged 53)
Paris, France
Known for Dulong–Petit law

Pierre Louis Dulong FRS FRSE ( /dˈlɒŋ, -ˈlŋ/ ; French:  [dylɔ̃] ; 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. He collaborated several times with fellow scientist Alexis Petit, the co-creator of the Dulong–Petit law.

France Republic with mainland in Europe and numerous oversea territories

France, officially the French Republic, is a country whose territory consists of metropolitan France in Western Europe and several overseas regions and territories. The metropolitan area of France extends from the Mediterranean Sea to the English Channel and the North Sea, and from the Rhine to the Atlantic Ocean. It is bordered by Belgium, Luxembourg and Germany to the northeast, Switzerland and Italy to the east, and Andorra and Spain to the south. The overseas territories include French Guiana in South America and several islands in the Atlantic, Pacific and Indian oceans. The country's 18 integral regions span a combined area of 643,801 square kilometres (248,573 sq mi) and a total population of 67.3 million. France, a sovereign state, is a unitary semi-presidential republic with its capital in Paris, the country's largest city and main cultural and commercial centre. Other major urban areas include Lyon, Marseille, Toulouse, Bordeaux, Lille and Nice.

Physicist scientist who does research in physics

A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate causes of phenomena, and usually frame their understanding in mathematical terms. Physicists work across a wide range of research fields, spanning all length scales: from sub-atomic and particle physics, through biological physics, to cosmological length scales encompassing the universe as a whole. The field generally includes two types of physicists: experimental physicists who specialize in the observation of physical phenomena and the analysis of experiments, and theoretical physicists who specialize in mathematical modeling of physical systems to rationalize, explain and predict natural phenomena. Physicists can apply their knowledge towards solving practical problems or to developing new technologies.

Chemist scientist trained in the study of chemistry

A chemist is a scientist trained in the study of chemistry. Chemists study the composition of matter and its properties. Chemists carefully describe the properties they study in terms of quantities, with detail on the level of molecules and their component atoms. Chemists carefully measure substance proportions, reaction rates, and other chemical properties. The word 'chemist' is also used to address Pharmacists in Commonwealth English.


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 [1] before entering the École Polytechnique, Paris in 1801, only for his studies to be impeded by poor health. [2] He began studying medicine, but gave this up, possibly because of a lack of financial means, [2] to concentrate on science, working under the direction of Thénard.

Auxerre Prefecture and commune in Bourgogne-Franche-Comté, France

Auxerre is the capital of the Yonne department and the fourth-largest city in Burgundy. Auxerre's population today is about 39,000; the metropolitan area comprises roughly 92,000 inhabitants. Residents of Auxerre are referred to as Auxerrois.

École Polytechnique French institution of higher education and research in Palaiseau

École polytechnique is a French public institution of higher education and research in Palaiseau, a suburb southwest of Paris. It is one of the most prestigious and selective French scientific and engineering schools, called grandes écoles in French. It is known for its ingénieur polytechnicien scientific degree program which is equivalent to both a bachelor and master of science. Its entrance exam, the X-ENS exam, is renowned for its selectivity with a little over 500 admitted students out of the 53 848 students enrolled in the preparatory programs for the French scientific and engineering schools entrance exams.

Paris Capital of France

Paris is the capital and most populous city of France, with an area of 105 square kilometres and an official estimated population of 2,140,526 residents as of 1 January 2019. Since the 17th century, Paris is one of Europe's major centres of finance, diplomacy, commerce, fashion, science, and the arts.


In chemistry, he contributed to knowledge on:

Nitrous acid chemical compound

Nitrous acid (molecular formula HNO2) is a weak and monobasic acid known only in solution and in the form of nitrite (NO
) salts. Nitrous acid is used to make diazonium salts from amines. The resulting diazonium salts are reagents in azo coupling reactions to give azo dyes.

Oxide chemical compound with at least one oxygen atom

An oxide is a chemical compound that contains at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion of oxygen, an O2– atom. Metal oxides thus typically contain an anion of oxygen in the oxidation state of −2. Most of the Earth's crust consists of solid oxides, the result of elements being oxidized by the oxygen in air or in water. Hydrocarbon combustion affords the two principal carbon oxides: carbon monoxide and carbon dioxide. Even materials considered pure elements often develop an oxide coating. For example, aluminium foil develops a thin skin of Al2O3 (called a passivation layer) that protects the foil from further corrosion. Individual elements can often form multiple oxides, each containing different amounts of the element and oxygen. In some cases these are distinguished by specifying the number of atoms as in carbon monoxide and carbon dioxide, and in other cases by specifying the element's oxidation number, as in iron(II) oxide and iron(III) oxide. Certain elements can form many different oxides, such as those of nitrogen.

Phosphorus Chemical element with atomic number 15

Phosphorus is a chemical element with symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Earth. It has a concentration in the Earth's crust of about one gram per kilogram. With few exceptions, minerals containing phosphorus are in the maximally oxidized state as inorganic phosphate rocks.

Dulong also discovered the dangerously sensitive nitrogen trichloride in 1811, losing three fingers and an eye in the process. [3] The fact that Dulong kept the accident a secret meant that Sir Humphrey Davy's investigation of the compound had the same unfortunate consequence, although Davy's injuries were less severe. [4]

Nitrogen trichloride chemical compound

Nitrogen trichloride, also known as trichloramine, is the chemical compound with the formula NCl3. This yellow, oily, pungent-smelling and explosive liquid is most commonly encountered as a byproduct of chemical reactions between ammonia-derivatives and chlorine (for example, in swimming pools).

Humphry Davy Cornish chemist

Sir Humphry Davy, 1st Baronet was a Cornish chemist and inventor, who is best remembered today for isolating, using electricity, a series of elements for the first time: potassium and sodium in 1807 and calcium, strontium, barium, magnesium and boron the following year, as well as discovering the elemental nature of chlorine and iodine. He also studied the forces involved in these separations, inventing the new field of electrochemistry. In 1799 Davy experimented with nitrous oxide and was astonished at how it made him laugh, so he nicknamed it "laughing gas", and wrote about its potential anaesthetic properties in relieving pain during surgery.

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". [5]

Royal Society English learned society for science

The President, Council and Fellows of the Royal Society of London for Improving Natural Knowledge, commonly known as the Royal Society, is a learned society. Founded on 28 November 1660, it was granted a royal charter by King Charles II as "The Royal Society". It is the oldest national scientific institution in the world. The society is the United Kingdom's and Commonwealth of Nations' Academy of Sciences and fulfils a number of roles: promoting science and its benefits, recognising excellence in science, supporting outstanding science, providing scientific advice for policy, fostering international and global co-operation, education and public engagement.

In 1815, Dulong collaborated for the first time with Alexis Petit, in publishing a paper on heat expansion. [6] 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. [7] This law, though largely discredited in modern times, helped develop the periodic table and, more broadly, the examination of atomic masses. [7]

Alexis Thérèse Petit was a French physicist.

Metal element, compound, or alloy that is a good conductor of both electricity and heat

A metal is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typically malleable or ductile. A metal may be a chemical element such as iron, or an alloy such as stainless steel.

Chemical element a species of atoms having the same number of protons in the atomic nucleus

A chemical element is a species of atom having the same number of protons in their atomic nuclei. For example, the atomic number of oxygen is 8, so the element oxygen consists of all atoms which have exactly 8 protons.

In 1818, Dulong was honored by the French Academy for work that would contribute to his co-discovery of the Dulong–Petit law.

In 1820, Dulong succeeded Petit (1791-1820), who retired due to poor health, [6] as professor of physics at École Polytechnique. Dulong studied the elasticity of steam, the measurement of temperatures, and the behavior of elastic fluids. He studied how metals enabled the combinations of certain gases. [8] 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. His is one of the names of 72 scientists inscribed on the Eiffel Tower. 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. [8]

Roberto Piazza’s 2016 paper [9] on the Dulong–Petit law provides biographical and temperament details by contemporary and fellow physicist, Jules Jamin. “Petit had a lively intelligence, an elegant and easy speech, he seduced with an amiable look, got easily attached, and surrendered himself to his tendencies rather than governing them. He was credited with an instinctive scientific intuition, a power of premature invention, certain presages of an assured future that everyone foresaw and even desired, so great was the benevolence which he inspired. Dulong was the opposite: His language was thoughtful, his attitude serious and his appearance cold[. . . ] He worked slowly but with certainty, with a continuity and a power of will that nothing stopped, I should say with a courage that no danger could push back. In the absence of that vivacity of the mind which invents easily, but likes to rest, he had the sense of scientific exactness, the gusto for precision experiments, the talent of combining them, the patience of completing them, and the art, unknown before him, to carry them to the limits of accuracy[. . . ] Petit had more mathematical tendency, Dulong was more experimental; the first carried in the work more brilliant easiness, the second more continuity; One represented imagination, the other reason, which moderates and contains it.”

Personal life

He was married to Emelie Augustine Riviere in 1803. [10]

Socially, Dulong was often dismissed as a dry, standoffish individual. His few friends disagreed with this view, viewing his personality as subdued rather than dull. [6]

The modern-day Tour Clovis, the tower Dulong climbed to conduct his experiments on steam. Tour clovis h4.jpg
The modern-day Tour Clovis, the tower Dulong climbed to conduct his experiments on steam.

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 St. 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. [11]

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 Sir Humphrey Davy. [6]


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. [6]

He is buried in Père Lachaise Cemetery. His monument was paid for by his scientific peers. [6]

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  1. Lycée Pierre Corneille de Rouen - History
  2. 1 2 Fox, Robert (1968). "The Background to the Discovery of Dulong and Petit's Law". The British Journal for the History of Science. 4: 1–22. doi:10.1017/s0007087400003150. JSTOR   4024983.
  3. Thénard J. L.; Berthollet C. L. (1813). "Report on the work of Pierre Louis Dulong". Annales de Chimie et de Physique . 86 (6): 37–43.
  4. Hale, William (April 1888). "Formation of the Explosive Chloride of Nitrogen by Electrolysis". Science. 11: 206. Bibcode:1888Sci....11..206H. doi:10.1126/science.ns-11.273.206. JSTOR   1764740.
  5. Britain), Royal Society (Great (1837-01-01). Abstracts of the Papers Printed in the Philosophical Transactions of the Royal Society of London. Richard Taylor.
  6. 1 2 3 4 5 6 Lemay, Pierre (1948). "Pierre Louis Dulong, His Life and Work". Chymia. 1: 171–190. JSTOR   27757122.
  7. 1 2 Laing, Mary; Laing, Michael (2006). "Dulong and Petit's Law: We Should Not Ignore Its Importance". Journal of Chemical Education. 83 (10): 1499–1504. Bibcode:2006JChEd..83.1499L. doi:10.1021/ed083p1499.
  8. 1 2 "Pierre-Louis Dulong | French scientist". Encyclopedia Britannica. Retrieved 2017-05-05.
  9. The strange case of Dr. Petit and Mr. Dulong, Roberto Piazza, arXiv, 2018-07-06
  10. Biographical Index of Former Fellows of the Royal Society of Edinburgh 1783–2002 (PDF). The Royal Society of Edinburgh. July 2006. ISBN   0 902 198 84 X.
  11. "Dulong, Pierre Louis". 1911 Encyclopædia Britannica. 8.

Further reading