François-Marie Raoult
Encyclopedia
François-Marie Raoult was a French chemist who conducted research into the behavior of solutions, especially their physical properties.
, in the département of Nord. He became aspirant répétiteur at the Lycée of Reims
in 1853, and after holding several intermediate positions was appointed in 1862 to the professorship of chemistry
in Sens
lycée. There he prepared a thesis on electromotive force
which gained him a doctor's degree in Paris the following year.
In 1867 Raoult was put in charge of chemistry classes at Grenoble
, and three years later he succeeded to the chair of chemistry, which he held until his death in 1901. Raoult's earliest researches were physical in character, being largely concerned with the phenomena of the voltaic cell; later there was a period when more purely chemical questions engaged his attention.
Raoult's name is best known in connection with work on solution
s, to which he devoted the last two decades of his life. His first paper describing how solutes depressed the freezing points
of solutions was published in 1878. Further experiments with various solvent
s, such as benzene
and acetic acid
, in addition to water, led him to believe in a simple relation between the molecular weights of a solute and the freezing-point
of a solution. He expressed the relationship as the loi générale de la congélation, that if one molecule
of a substance be dissolved in 100 molecules of any given solvent, the temperature of solidification of the latter will be lowered by 0.63 °C. Another relation on which Raoult worked was that concerning the depression of a solvent's vapor pressure
, due to a solute, showing that the decrease is proportional to the solute's molecular weight. This relationships holds best in the limiting case of a dilute solution. These two generalizations afforded a new method of determining the molecular weights of dissolved substances, and were utilized by Jacobus van 't Hoff
and Wilhelm Ostwald
, among other chemists, in support of the hypothesis of electrolytic dissociation in solutions. Raoult's freezing-point depression method became even more useful after it was improved by Ernst Otto Beckmann
and became a standard technique for determining molecular weights of organic substances.
An account of Raoult's life and work was given by Professor van 't Hoff in a memorial lecture delivered before the London Chemical Society
on the 26th of March 1902.
Life and work
Raoult was born at FournesFournes-en-Weppes
-References:*...
, in the département of Nord. He became aspirant répétiteur at the Lycée of Reims
Reims
Reims , a city in the Champagne-Ardenne region of France, lies east-northeast of Paris. Founded by the Gauls, it became a major city during the period of the Roman Empire....
in 1853, and after holding several intermediate positions was appointed in 1862 to the professorship of chemistry
Chemistry
Chemistry is the science of matter, especially its chemical reactions, but also its composition, structure and properties. Chemistry is concerned with atoms and their interactions with other atoms, and particularly with the properties of chemical bonds....
in Sens
Sens
Sens is a commune in the Yonne department in Burgundy in north-central France.Sens is a sub-prefecture of the department. It is crossed by the Yonne and the Vanne, which empties into the Yonne here.-History:...
lycée. There he prepared a thesis on electromotive force
Electromotive force
In physics, electromotive force, emf , or electromotance refers to voltage generated by a battery or by the magnetic force according to Faraday's Law, which states that a time varying magnetic field will induce an electric current.It is important to note that the electromotive "force" is not a...
which gained him a doctor's degree in Paris the following year.
In 1867 Raoult was put in charge of chemistry classes at Grenoble
Grenoble
Grenoble is a city in southeastern France, at the foot of the French Alps where the river Drac joins the Isère. Located in the Rhône-Alpes region, Grenoble is the capital of the department of Isère...
, and three years later he succeeded to the chair of chemistry, which he held until his death in 1901. Raoult's earliest researches were physical in character, being largely concerned with the phenomena of the voltaic cell; later there was a period when more purely chemical questions engaged his attention.
Raoult's name is best known in connection with work on solution
Solution
In chemistry, a solution is a homogeneous mixture composed of only one phase. In such a mixture, a solute is dissolved in another substance, known as a solvent. The solvent does the dissolving.- Types of solutions :...
s, to which he devoted the last two decades of his life. His first paper describing how solutes depressed the freezing points
Freezing-point depression
Freezing-point depression describes the phenomenon in which the freezing point of a liquid is depressed when another compound is added, meaning that a solution has a lower freezing point than a pure solvent. This happens whenever a non-volatile solute is added to a pure solvent, such as water...
of solutions was published in 1878. Further experiments with various solvent
Solvent
A solvent is a liquid, solid, or gas that dissolves another solid, liquid, or gaseous solute, resulting in a solution that is soluble in a certain volume of solvent at a specified temperature...
s, such as benzene
Benzene
Benzene is an organic chemical compound. It is composed of 6 carbon atoms in a ring, with 1 hydrogen atom attached to each carbon atom, with the molecular formula C6H6....
and acetic acid
Acetic acid
Acetic acid is an organic compound with the chemical formula CH3CO2H . It is a colourless liquid that when undiluted is also called glacial acetic acid. Acetic acid is the main component of vinegar , and has a distinctive sour taste and pungent smell...
, in addition to water, led him to believe in a simple relation between the molecular weights of a solute and the freezing-point
Melting point
The melting point of a solid is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends on pressure and is usually specified at standard atmospheric pressure...
of a solution. He expressed the relationship as the loi générale de la congélation, that if one molecule
Molecule
A molecule is an electrically neutral group of at least two atoms held together by covalent chemical bonds. Molecules are distinguished from ions by their electrical charge...
of a substance be dissolved in 100 molecules of any given solvent, the temperature of solidification of the latter will be lowered by 0.63 °C. Another relation on which Raoult worked was that concerning the depression of a solvent's vapor pressure
Vapor pressure
Vapor pressure or equilibrium vapor pressure is the pressure of a vapor in thermodynamic equilibrium with its condensed phases in a closed system. All liquids have a tendency to evaporate, and some solids can sublimate into a gaseous form...
, due to a solute, showing that the decrease is proportional to the solute's molecular weight. This relationships holds best in the limiting case of a dilute solution. These two generalizations afforded a new method of determining the molecular weights of dissolved substances, and were utilized by Jacobus van 't Hoff
Jacobus Henricus van 't Hoff
Jacobus Henricus van 't Hoff, Jr. was a Dutch physical and organic chemist and the first winner of the Nobel Prize in chemistry. He is best known for his discoveries in chemical kinetics, chemical equilibrium, osmotic pressure, and stereochemistry...
and Wilhelm Ostwald
Wilhelm Ostwald
Friedrich Wilhelm Ostwald was a Baltic German chemist. He received the Nobel Prize in Chemistry in 1909 for his work on catalysis, chemical equilibria and reaction velocities...
, among other chemists, in support of the hypothesis of electrolytic dissociation in solutions. Raoult's freezing-point depression method became even more useful after it was improved by Ernst Otto Beckmann
Ernst Otto Beckmann
Ernst Otto Beckmann was a German chemist who is remembered for his invention of the Beckmann differential thermometer and for his discovery of the Beckmann rearrangement.-Scientific work:...
and became a standard technique for determining molecular weights of organic substances.
An account of Raoult's life and work was given by Professor van 't Hoff in a memorial lecture delivered before the London Chemical Society
Chemical Society
The Chemical Society was formed in 1841 as a result of increased interest in scientific matters....
on the 26th of March 1902.
Activities and honors
- Prix International de Chimie LaCaze (1889)
- Davy Medal (1892)
- Prix de l'Institut (1895)
- Commandeur de la Légion d'Honneur (1900)