Raoult , Francois-Marie

(1830–1901) French chemist

Raoult came from a poor background in Fournes-en-Weppes, France. He obtained his PhD in 1863 from the University of Paris and was 37 years old when he took up his first academic appointment at the University of Grenoble, where he was made professor of chemistry in 1870.

Raoult is noted for his work on the properties of solutions, in particular the effect of a dissolved substance in the lowering of freezing points. In 1882 he showed (Raoult's law) that the depression in the freezing point of a given solvent was proportional to the mass of substance dissolved divided by the substance's molecular weight. He later showed a similar effect for the vapor pressure of solutions. Measurement of freezing-point depression became an important technique for determining molecular weights.

Raoult's work was also important in validating Jacobus van't Hoff's theory of solutions. Also of significance in his work was his observation that the depression of the freezing point of water caused by an inorganic salt was double that caused by an organic solute (given the same molecular weight). This was one of the anomalies whose explanation led Sven Arrhenius to formulate his theory of ionic dissociation.