Pierre Louis Dulong

Pierre Louis Dulong (* February 12, 1785 in Rouen, † July 19, 1838 in Paris) was a French physician, physicist and chemist.

Life

He lost, as an only child, both parents at the age of 4 years. As a well -situated orphan, he was taken in by his aunt in Auxerre. He attended high school in Auxerre and then the Lycée Pierre Corneille in Rouen before 1801 passed the entrance examination at the École Polytechnique in Paris. First, he wanted to study there ship technology, but then occupied in the absence of a place in the artillery school. Health weaknesses but forced him to leave the artillery school before the end of the second year. P. L. Dulong occupied then at the École Polytechnique in Paris, physics and chemistry.

He began the study of human medicine, studied and worked as a doctor for some time in a poor neighborhood in Paris, the Faubourg Saint -Marceau. He then turns to the natural sciences such as botany at will employees in the chemical laboratory of Claude -Louis Berthollet (1748-1822), where he among other things, operates on the solubility of salts. P. L. Dulong also learned the tremendous explosiveness of Stickstofftrichlorids ( NCl3 ) know, in 1812, he lost two fingers and an eye in one of his experiments. In 1820 he was appointed Director of Studies, then a professor at the École Polytechnique and 1830.

Since 1823 he was a member of the Académie des sciences in 1832 and its permanent secretary. As of July 1807, he was mentioned in the Memoires de Physique et de Chimie de la Société d' Arcueil as a member of the Société d' Arcueil. He is immortalized in particular on the Eiffel Tower, see: The 72 names on the Eiffel Tower.

Pierre Louis Dulong died on 19 July 1838 in Paris.

Scientific achievements

PLDulong is best known by the mitbenannte after him Dulong - Petit law, that the specific heat capacity of solids, eg Metals associated with their molar mass. The fact that this is a rule that you can see the fact that there are differences especially for elements with lower atomic mass and at lower temperatures. He made this discovery together with Alexis Thérèse Petit ( 1791-1820 ). Both discovered in the year 1818/1819 the law of the constancy of the atomic heats (see also Chemistry in the modern era ).

The product of specific heat and atomic mass of solid elements is nearly constant and is on average 6.2 cal:

From this context, the approximate atomic mass of solids can be determined due to the estimation of atomic mass ≈ 6.2 / spec. Heat. The determination is not very accurate because the value 6.2 represents only an average.

Today, this relationship can be explained as follows: The possible movements of the atoms of a solid body are limited and done in elastic vibrations at certain centers of gravity in the crystal lattice. There are formally only three degrees of freedom or movement possibilities in the three-dimensional space. From an energy point of view but each degree of freedom is counted twice, as not only kinetic energy is stored ( during oscillation of atoms), but also potential energy. For heating a defined amount of a solid body by 1 ° C at constant volume Cv is the amount of heat (or atomic heat at constant volume ) of:

He also dealt with the structure elucidation of Stickstofftrichlorids (1811 ), where he by the explosions of this dangerous compound one eye and three fingers lost. Also he succeeded in the synthesis of phosphinic acid (1816 ).

In 1815, almost simultaneously with Humphry Davy ( 1778-1829 ), he proposed the hydrogen theory of acids (see acid-base concepts ) before.

Works

  • Dulong, PL: Recherches sur la mutuelle Decomposition of insolubles sels et des sels solubles. Annales de Chimie, t. LXXXII
  • Dulong, PL: Mémoire sur une nouvelle matière détonante ( Mémoires de la Société d' Arcueil, t III. );
  • Dulong, PL: Recherches sur les lois de la dilatation of the solid, the most liquid of the fluid élastiques et, et sur ​​la mesure exacte of températures. Annales de Chimie et de Physique, t. II
  • Dulong, PL: Observations sur quelques combinaisons de l' azote et de l' oxygène ( ibid.);
  • Dulong, PL: Mémoire sur les combinaisons you phosphore avec l' oxygène ( Mémoires de la Société d' Arcueil, t III. );
  • Dulong, PL: Recherches sur la mesure et sur ​​les lois of températures de la communication de la chaleur. Annales de Chimie et de Physique, t. VIl
  • Dulong, PL: Recherches sur quelques points importants de la théorie de la chaleur. ( ibid., X t. );
  • Dulong, PL: Nouvelle determination of the proportions de l' eau et de la densité de quelques fluid élastiques. ( ibid., t XV. );
  • Dulong, PL: Notes sur la propriété que quelques possèdent métaux de la combinaison faciliter of fluid élastiques. ( Mémoires de l'Institut, t V. );
  • Dulong, PL: Recherches sur les pouvoirs réfringents of fluid élastiques ( ibid., X t. );
  • Dulong, PL: Recherches sur la force de la vapeur d' eau élastique ( ibid., X t. );
  • Dulong, PL: Rapport fait le 9 janvier 1832 avec MM Arago, Prony et Cordier, Mémoire sur un relatif aux appareils producteurs de la vapeur, lu à l' Académie des Sciences, par le baron Seguier; Paris, 1832, in-8 °
France List of the 72 names on the Eiffel Tower Chemical element Integrated Authority File
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