When diluting a hydroalcoholic mixture with water, the final volume is lower than the sum of the volume of water + the starting volume.
This article explains its origin. He presents a study which demonstrates that in the case where analysis by distillation requires dilution, it is nevertheless possible to obtain good precision in the measurement of the alcohol level.
To measure the alcohol content in a spirit, the official method by distillation is still the most used method because it is the most universal and the least expensive in investment.
There are different types of distillation devices (direct distillation or steam entrainment), more or less automated, but which all have a maximum field of application for measuring the alcohol level.
This article explains how to use the device even if the alcohol level is above its use limit, while obtaining accurate results using appropriate methodology.
To meet internal production control requirements, this article presents the various methods and equipment for measuring the alcohol content in alcoholic beverages.
It guides you in choosing the most suitable method based on your objectives, whether in terms of the type of beverage to be analyzed, the desired result accuracy, response time, frequency of analysis, operator qualifications, or budget constraints linked to investment and operation.
The official method for determining the alcohol content of a spirit requires prior distillation to eliminate residues that could distort the density measurement. However, distillation does not completely eliminate all volatile compounds other than ethanol.
What about measurements made with automatic or semi-automatic devices, very selective for the analysis of ethanol, such as near infrared analyzers?
During a temperature increase, volume of alcohols expands or conversely, during a temperature decrease, the volume contracts. The higher the alcohol content, the more pronounced this phenomenon becomes.
In the field of spirits, during production, for inventory management and bulk transactions, the measured volume can vary significantly due to temperature fluctuations. Therefore, it is essential to convert the measured volumes to 20°C for accuracy.
So how to calculate the volume at 20°C ?