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Common errors during the determination of alcohol by distillation

Volume measurements

Leaks

Temperature Measurements

Hydrometer Measurements






















• Volume measurements are the most critical part of this technique.
  
  Make sure you read the method for using a volumetric flask correctly.
  
  If you do not have a hot/cold water bath to bring the temperature of the wine and the collected distillate up/down to 20^oC for an accurate measurement of 250ml, at least make sure that -
  
  
  • the volume of the wine and diluted distillate is measured accurately by -
    
    
    • using the same volumetric flask
      
      
    • and measuring both at the same temperature.
      
      
• Leaks anywhere in the apparatus, can allow alcohol to escape and be lost through these leaks, giving a false low reading.
  
  
  • Make sure all joints are secure (see safety note).
    
    
  • Make sure that the end of the adaptor receiver protrudes well below the water or distillate in the volumetric receiving flask (see diagram).
    
    This can best be achieved by attaching a small piece of plastic tubing to the end of the adapter reciever to obtain the appropriate length and to prevent breakage of the bottom of the receiving volumetric flask.
    
    
• Loss of alcohol can also occur through evaporation of the warm distillate from the volumetric receiving flask, however, this can be prevented by seating the flask in a cold water bath, packed with ice.
  
  ALso make sure that an adequate water flow is running through the condenser jacket .
  
  Also see leaks.
  
  
• Measure and record the temperature of your distillate solution as soon as possible after taking a reading of the apparent alcohol concentration with your alcohol hydrometer.
  
  Then apply the appropriate correction from the alcohol-temperature correction table to calculate and record the true alcohol concentration.
  
  
• Hydrometer measurement errors should also be checked