Alcohol Content Determination in Spirits

All You Need to Know

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What Is Alcohol Content Determination?
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The Distillation Process
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Definition/Information

A hollow glass tube is filled and vibrates at a certain frequency. This frequency is measured and converted into density. A built-in Peltier thermostat controls the temperature of the benchtop instrument.

Learn how to measure spirits in the application note.

Discover the digital density meter here.

Advantages

  • Automatic measurement
  • Automatic conversion of density into respective alcohol unit
  • Relatively short analysis time (1-3 min)
  • Efficient cleaning. Fast drying with pump
  • Built-in Peltier temperature control (benchtop instruments)
  • Large storage capacity for results and data management

Disadvantages

  • Higher initial investement costs

Manual

Hydrometer

Definition/Information

A hydrometer is a glass instrument,used to determine the specific gravity of liquids based on the buoyancy principle. The lighter the liquid, the higher the alcohol concentration.

Advantages

  • Simple, inexpensive
  • Quick check

Disadvantages

  • Long analysis duration due to time for temperature equilibration
  • Small measuring range, typically takes 20 hydrometers to cover a wide measuring range
  • Large sample volume required (140 mL to 600 mL)
  • Breakable

Manual

Pycnometer

Definition/Information

A pycnometer is a glass flask, that has a defined volume and mass. The density is established by determining the exact mass of liquids by filling the entire instrument's volume at a set temperature.

Learn how to choose, use and calibrate pycnometers

Advantages

  • Inexpensive
  • Directly related to the definition of density (mass divided by volume)

Disadvantages

  • Pycnometers are calibrated for a certain temperature (measurements are only valid at that temperature)
  • Measurement is time consuming (up to 25 min / sample)
  • Density manually calculated and converted into the desired alcohol unit
  • Typical sample volume required is 25 mL
  • High level of user training required to ensure accurate measurements

Discover more about all the instrument here.

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What is alcohol?

Alcohol or more precisely ethanol is the alcohol predominantly present in all alcoholic beverages. In chemistry, ethanol is represented as the condensed formula CH3CH2OH or the abbreviation EtOH. It is a volatile, flammable organic compound and mostly used as a solvent. Ethanol in the alcohol family is the only alcohol that humans can consume without enduring immediate health damage. Other alcohols are toxic even in small doses and will cause permanent health damage (e.g. methanol).

Why do we need to distill a sample before measuring it?

Alcohol content is determined via density, however density is not specific to alcohol and water. Other substances present in the mixture of interest will have an impact on the density. Measuring the density is not a method of identification, thereby purifying the alcohol by distillation ensures that the mixture will contain only alcohol and water.

Does temperature affect alcohol measurement?

Alcohol is determined via density measurement, which is temperature dependent. If an operator is using a hydrometer or a pycnometer, someone needs to take note of the temperature to apply the correct correction factor. Today, most of the digital instruments are provided with a temperature sensor or temperature control. More information on digital density meters can be found here.

What is the maturation process?

The maturation of spirits is performed by storing the distillated alcohol in a barrel or a earthenware jar during a define period of time. The container made of wood or soil will give a certain "character" to the liquor, its flavor and a characteristic yellow to dark black color. The alcohol before this process is practically tasteless and colorless.

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