Measuring instrument (ebullioscope, ebulliometer) for determining the alcohol content in alcoholic liquids. The first ebullioscopes were developed by Émile Hilaire Amagat, François Marie Raoult, Brossard-Vidal, E. Malligand and Tabarié. Ebullioscopy is the determination of the molecular weight of a liquid from the molecular increase in boiling point. The principle of alcohol determination by means of ebullioscopy is based on the fact that the boiling point of wine decreases with increasing alcohol content. The alcohol type ethanol has a lower boiling point of 78 °C than water. The lower the boiling point of the wine, the higher the alcohol content.
The exact boiling point of the water must be determined for the respective air pressure and the device adjusted accordingly in a first measuring run. For fully fermented wines, the alcohol content is measured by heating the unchanged wine. For wines with a very high content of residual sugar, the wine must be diluted 1:1 with water before the determination and then the determined alcohol value must be doubled. Likewise, this is necessary for an alcohol content of more than 25% vol. Therefore, the device is only conditionally suitable for distillates. In contrast to the so-called Rebelein method, no chemistry is required for the measurement. See other methods under analytical testing.
Description of how the Vidal ebullioscope works (diagram on the left). The measuring device consists of a small metal kettle (D), which holds the wine to be heated to boiling (heating device E). Attached to this is a small reflux condenser (A) in which the evaporated liquid is cooled and drips back into the vessel via a pipette (B). In the vapour space is the mercury-filled thermometer (C), on the scale of which the alcohol contents are read directly rather than the temperature degrees. At the very bottom is a drain cock (F).
Graphic text: WIKIPEDIA ebullioscope
Ebullioscope (left): by Userfaf9369 - Own work, public domain, link
Ebullioscope (right): By P. Doré - P. Doré, Public domain, Link
