Ebullioscope Explained

In physics, an ebullioscope 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. 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.^{[1] [2]}

A famous ebullioscope variant was built by Pierre Marie Edouard Malligand, patented in 1876.^[3] 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.

A later version was built by the French chemist François-Marie Raoult,^[4] but the difficulty of determining the exact temperature was overcome by the invention of the Beckmann thermometer by Ernst Otto Beckmann in 1887.^[5] This improvement made the ebullioscope a standard apparatus to determine the molecular weight of substances in solution by using the ebullioscopic constant of the solvent.

See also

• Ebulliometer

References

1. See:
   • P. Doré. Leçons de chimie élémentaire appliquées aux arts industriels …, (Paris, France: Victor Dalmont, 1857), pages 323-325.
   • Brossard Vidal, Observations sur les instruments de l'administration et du commerce pour reconnaître la richesse alcoolique des liquides spiritueux (Paris, France: A. Henry, 1842)
   • Ad. Chambon (1845), "Considérations sur l'Ebullioscope alcoométrique de MM. Vaille et Vidal Brossard," Répertoire des Travaux de la Société de Statisque, 8 : 93-98.
   • Louis-François Desbordes and Honoré Brossard-Vidal, "alcoomètre Vidal," French patent 415 (filed: November 23, 1844; issued: June 18, 1845), Bulletin des lois du Royaume de France (1846), 9th series, vol. 31, page 72.
2. See:
   • E. Malligand and E. Brossard-Vidal (May 25, 1874) "Sur l'ébullioscope Vidal," Comptes rendus, 78 : 1470-1471.
   • [Anon.] (July 17, 1874) Chemical Notices from Foreign Sources: "Vidal Ebullioscope," The Chemical News and Journal of Physical Science, 30 (762) : 30.
3. Pierre M. E. Malligand - Improvement in Ebullioscope, No. 173 128, February 8 1876 https://museo.pastafabbri.it/wp-content/uploads/2018/07/US-patent-Ebullioscopes-Malligand.pdf
4. R. Lespieau (1890) "Sur l'ébullioscope de M. Raoult," Bulletin de la Société chimique de France, 3rd series, 3 : 855-858.
5. 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.