An ebullioscope (from the Latin ''ēbullīre'' (to boil) + -scope) is an instrument for measuring the boiling point of a liquid. This can be used for determining the alcoholic strength of a mixture, or for determining the molecular weight of a non-volatile solute based on the

boiling-point elevation Boiling-point elevation describes the phenomenon that the boiling point of a liquid (a solvent) will be higher when another compound is added, meaning that a solution has a higher boiling point than a pure solvent. This happens whenever a non-vo ...

. The procedure is known as ebullioscopy. The first ebullioscope was invented in 1838 by Honoré Brossard-Vidal, and was used for measuring alcoholic content. The advantage of this method was that the boiling point is relatively insensitive to other components such as sugars. Older alcoholimeters were based on measuring the density, which is more sensitive to the presence of other solutes. A famous ebullioscope variant was built by Pierre Marie Edouard Malligand, patented in 1876 The device is used by winemakers still to this day to measure the alcohol contents of wines, using the "Malligand degree" (M°) as a unit of measure.{{Citation needed, date=September 2022 A later version was built by the French chemist

François-Marie Raoult François-Marie Raoult (; 10 May 1830 – 1 April 1901) was a French chemist who conducted research into the behavior of solutions, especially their physical properties. Life and work Raoult was born at Fournes, in the ''département'' of Nor ...

, but the difficulty of determining the exact temperature was overcome by the invention of the

Beckmann thermometer A Beckmann thermometer is a device used to measure small differences of temperature, but not absolute temperature values. It was invented by Ernst Otto Beckmann (1853 – 1923), a German chemist, for his measurements of colligative properties ...

Ernst Otto Beckmann Ernst Otto Beckmann (July 4, 1853 – July 12, 1923) was a German pharmacist and chemist who is remembered for his invention of the Beckmann differential thermometer and for his discovery of the Beckmann rearrangement. Scientific work Ernst Ott ...

in 1887.Ernst Beckmann (1888
"Über die Methode der Molekulargewichtsbestimmung durch Gefrierpunkterneidrigung"
(On the method for the determination of molecular weights by freezing point depression), ''Zeitschrift der Physikalische Chemie'', 2 : 638-715; see especially p. 644. This improvement made the ebullioscope a standard apparatus to determine the

molecular weight A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and bioch ...

of substances in solution by using the

ebullioscopic constant In thermodynamics, the ebullioscopic constant relates molality to boiling point elevation. It is the ratio of the latter to the former: :\Delta T = iK_\text b * is the van 't Hoff factor, the number of particles the solute splits into or forms ...

of the solvent.

References

Laboratory equipment

See also

References