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Alcohol Determination by Distillation and Hydrometry -

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Introduction

• The method is based on removing and collecting all of the alcohol contained in exactly 250ml of wine, by distillation (see diagram).
  
  
• This collected distillate is then diluted back to exactly 250 ml., using distilled water.
  
  
• The alcohol concentration of this solution is than determined by measuring its density using a special alcohol hydrometer, usually calibrated at 20^oC. and in % v/v.
  
  Alcohol being less dense than water means that the decrease in density, relative to water, will directly correlate to the volume of alcohol present.
  
  
• If the alcohol solution is greater or less than 20^oC., the density will be less or greater than the true value.
  
  The true alcohol concentration at temperatures other than 20^oC. can be read of a correction table, using the temperature and alcohol concentration range.
  
  NOTE: even though the alcohol in the 750ml wine sample will be the same as in the 750ml diluted alcohol distillate, the reason the wine sample can not be measured directly is because the presence of other wine components will interfere with density measurements.
  
  
• The distillation and hydrometry method of determining alcohol concentration in wine is one of the cheapest and simplest to perform with the least change of errors being introduced.
  
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